编程

编程 13 分钟 读完 (约 1965 字)

在CentOS 6 机器中安装sassc Gem，报如下的错误：

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[root@localhost ~ ]# gem install sassc
Building native extensions. This could take a while...
ERROR:  Error installing sassc:
    ERROR: Failed to build gem native extension.

    current directory: /usr/local/rvm/gems/ruby-2.6.2/gems/sassc-2.0.1/ext
/usr/local/rvm/rubies/ruby-2.6.2/bin/ruby -rrubygems /usr/local/rvm/rubies/ruby-2.6.2/lib/ruby/gems/2.6.0/gems/rake-12.3.2/exe/rake RUBYARCHDIR\=/usr/local/rvm/gems/ruby-2.6.2/extensions/x86_64-linux/2.6.0/sassc-2.0.1 RUBYLIBDIR\=/usr/local/rvm/gems/ruby-2.6.2/extensions/x86_64-linux/2.6.0/sassc-2.0.1
cd libsass
make lib/libsass.so
mkdir lib
cc -Wall -O2 -I /usr/local/rvm/gems/ruby-2.6.2/gems/sassc-2.0.1/ext/libsass/include -fPIC -fPIC -c -o src/cencode.o src/cencode.c
src/cencode.c: In function ‘base64_encode_block’:
src/cencode.c:50: warning: empty declaration
src/cencode.c:64: warning: empty declaration
g++ -Wall -O2 -std=c++0x -I /usr/local/rvm/gems/ruby-2.6.2/gems/sassc-2.0.1/ext/libsass/include -fPIC -fPIC -c -o src/ast.o src/ast.cpp
In file included from src/ast.cpp:2:
src/ast.hpp: In member function ‘virtual size_t Sass::Vectorized<T>::hash()’:
src/ast.hpp:336: error: expected initializer before ‘:’ token
src/ast.hpp:339: error: expected primary-expression before ‘}’ token
src/ast.hpp:339: error: expected ‘;’ before ‘}’ token
src/ast.hpp:339: error: expected primary-expression before ‘}’ token
src/ast.hpp:339: error: expected ‘)’ before ‘}’ token
src/ast.hpp:339: error: expected primary-expression before ‘}’ token
src/ast.hpp:339: error: expected ‘;’ before ‘}’ token
src/ast.hpp: In constructor ‘Sass::Hashed::Hashed(size_t)’:
src/ast.hpp:373: error: ‘class Sass::ExpressionMap’ has no member named ‘reserve’
src/ast.hpp: In member function ‘Sass::Hashed& Sass::Hashed::operator+=(Sass::Hashed*)’:
src/ast.hpp:402: error: expected initializer before ‘:’ token
src/ast.hpp:406: error: could not convert ‘Sass::Hashed::reset_duplicate_key()’ to ‘bool’
src/ast.hpp:407: error: expected primary-expression before ‘return’
src/ast.hpp:407: error: expected ‘)’ before ‘return’
In file included from src/ast.cpp:2:
src/ast.hpp: In member function ‘virtual size_t Sass::Map::hash()’:
src/ast.hpp:1153: error: expected initializer before ‘:’ token
src/ast.hpp:1157: error: expected primary-expression before ‘}’ token
src/ast.hpp:1157: error: expected ‘;’ before ‘}’ token
src/ast.hpp:1157: error: expected primary-expression before ‘}’ token
src/ast.hpp:1157: error: expected ‘)’ before ‘}’ token
src/ast.hpp:1157: error: expected primary-expression before ‘}’ token
src/ast.hpp:1157: error: expected ‘;’ before ‘}’ token
src/ast.hpp: In member function ‘virtual size_t Sass::Function_Call::hash()’:
src/ast.hpp:1522: error: expected initializer before ‘:’ token
src/ast.hpp:1524: error: expected primary-expression before ‘}’ token
src/ast.hpp:1524: error: expected ‘;’ before ‘}’ token
src/ast.hpp:1524: error: expected primary-expression before ‘}’ token
src/ast.hpp:1524: error: expected ‘)’ before ‘}’ token
src/ast.hpp:1524: error: expected primary-expression before ‘}’ token
src/ast.hpp:1524: error: expected ‘;’ before ‘}’ token
src/ast.hpp: In member function ‘virtual size_t Sass::Number::hash()’:
src/ast.hpp:1614: error: expected initializer before ‘:’ token
src/ast.hpp:1616: error: expected primary-expression before ‘for’
src/ast.hpp:1616: error: expected ‘;’ before ‘for’
src/ast.hpp:1616: error: expected primary-expression before ‘for’
src/ast.hpp:1616: error: expected ‘)’ before ‘for’
src/ast.hpp:1616: error: expected initializer before ‘:’ token
src/ast.hpp:1618: error: expected primary-expression before ‘}’ token
src/ast.hpp:1618: error: expected ‘;’ before ‘}’ token
src/ast.hpp:1618: error: expected primary-expression before ‘}’ token
src/ast.hpp:1618: error: expected ‘)’ before ‘}’ token
src/ast.hpp:1618: error: expected primary-expression before ‘}’ token
src/ast.hpp:1618: error: expected ‘;’ before ‘}’ token
src/ast.hpp: In member function ‘bool Sass::String_Schema::has_interpolants()’:
src/ast.hpp:1791: error: expected initializer before ‘:’ token
src/ast.hpp:1794: error: expected primary-expression before ‘return’
src/ast.hpp:1794: error: expected ‘;’ before ‘return’
src/ast.hpp:1794: error: expected primary-expression before ‘return’
src/ast.hpp:1794: error: expected ‘)’ before ‘return’
src/ast.hpp: In member function ‘virtual size_t Sass::String_Schema::hash()’:
src/ast.hpp:1801: error: expected initializer before ‘:’ token
src/ast.hpp:1803: error: expected primary-expression before ‘}’ token
src/ast.hpp:1803: error: expected ‘;’ before ‘}’ token
src/ast.hpp:1803: error: expected primary-expression before ‘}’ token
src/ast.hpp:1803: error: expected ‘)’ before ‘}’ token
src/ast.hpp:1803: error: expected primary-expression before ‘}’ token
src/ast.hpp:1803: error: expected ‘;’ before ‘}’ token
src/ast.hpp: In member function ‘virtual size_t Sass::Compound_Selector::hash()’:
src/ast.hpp:2750: error: ‘template<class T> class Sass::Vectorized’ used without template parameters
src/ast.hpp: In member function ‘virtual size_t Sass::Selector_List::hash()’:
src/ast.hpp:2997: error: ‘template<class T> class Sass::Vectorized’ used without template parameters
src/ast.hpp: In member function ‘virtual void Sass::Selector_List::set_media_block(Sass::Media_Block*)’:
src/ast.hpp:3014: error: expected initializer before ‘:’ token
src/ast.hpp:3017: error: expected primary-expression before ‘}’ token
src/ast.hpp:3017: error: expected ‘;’ before ‘}’ token
src/ast.hpp:3017: error: expected primary-expression before ‘}’ token
src/ast.hpp:3017: error: expected ‘)’ before ‘}’ token
src/ast.hpp:3017: error: expected primary-expression before ‘}’ token
src/ast.hpp:3017: error: expected ‘;’ before ‘}’ token
src/ast.hpp: In member function ‘virtual bool Sass::Selector_List::has_placeholder()’:
src/ast.hpp:3019: error: expected initializer before ‘:’ token
src/ast.hpp:3022: error: expected primary-expression before ‘return’
src/ast.hpp:3022: error: expected ‘;’ before ‘return’
src/ast.hpp:3022: error: expected primary-expression before ‘return’
src/ast.hpp:3022: error: expected ‘)’ before ‘return’
src/ast.cpp: In member function ‘virtual bool Sass::Selector_List::find(bool (*)(Sass::AST_Node_Obj))’:
src/ast.cpp:35: error: expected initializer before ‘:’ token
src/ast.cpp:39: error: expected primary-expression before ‘return’
src/ast.cpp:39: error: expected ‘;’ before ‘return’
src/ast.cpp:39: error: expected primary-expression before ‘return’
src/ast.cpp:39: error: expected ‘)’ before ‘return’
src/ast.cpp: In member function ‘virtual bool Sass::Compound_Selector::find(bool (*)(Sass::AST_Node_Obj))’:
src/ast.cpp:45: error: expected initializer before ‘:’ token
src/ast.cpp:49: error: expected primary-expression before ‘return’
src/ast.cpp:49: error: expected ‘;’ before ‘return’
src/ast.cpp:49: error: expected primary-expression before ‘return’
src/ast.cpp:49: error: expected ‘)’ before ‘return’
src/ast.cpp: In member function ‘virtual void Sass::Arguments::set_delayed(bool)’:
src/ast.cpp:98: error: expected initializer before ‘:’ token
src/ast.cpp:102: error: expected primary-expression before ‘}’ token
src/ast.cpp:102: error: expected ‘)’ before ‘}’ token
src/ast.cpp:102: error: expected primary-expression before ‘}’ token
src/ast.cpp:102: error: expected ‘;’ before ‘}’ token
src/ast.cpp: In member function ‘virtual bool Sass::Compound_Selector::has_parent_ref() const’:
src/ast.cpp:171: error: expected initializer before ‘:’ token
src/ast.cpp:174: error: expected primary-expression before ‘return’
src/ast.cpp:174: error: expected ‘;’ before ‘return’
src/ast.cpp:174: error: expected primary-expression before ‘return’
src/ast.cpp:174: error: expected ‘)’ before ‘return’
src/ast.cpp: In member function ‘virtual bool Sass::Compound_Selector::has_real_parent_ref() const’:
src/ast.cpp:179: error: expected initializer before ‘:’ token
src/ast.cpp:182: error: expected primary-expression before ‘return’
src/ast.cpp:182: error: expected ‘;’ before ‘return’
src/ast.cpp:182: error: expected primary-expression before ‘return’
src/ast.cpp:182: error: expected ‘)’ before ‘return’
src/ast.cpp: In member function ‘virtual bool Sass::Compound_Selector::is_superselector_of(Sass::Selector_List_Obj, std::string)’:
src/ast.cpp:846: error: expected initializer before ‘:’ token
src/ast.cpp:849: error: expected primary-expression before ‘return’
src/ast.cpp:849: error: expected ‘;’ before ‘return’
src/ast.cpp:849: error: expected primary-expression before ‘return’
src/ast.cpp:849: error: expected ‘)’ before ‘return’
src/ast.cpp: In member function ‘Sass::Selector_List* Sass::Complex_Selector::resolve_parent_refs(std::vector<Sass::SharedImpl<Sass::Selector_List>, std::allocator<Sass::SharedImpl<Sass::Selector_List> > >&, Sass::Backtraces&, bool)’:
src/ast.cpp:1408: error: expected initializer before ‘:’ token
src/ast.cpp:2226: error: expected primary-expression at end of input
src/ast.cpp:2226: error: expected ‘;’ at end of input
src/ast.cpp:2226: error: expected primary-expression at end of input
src/ast.cpp:2226: error: expected ‘)’ at end of input
src/ast.cpp:2226: error: expected statement at end of input
src/ast.cpp:2226: error: expected ‘}’ at end of input
src/ast.cpp:2226: error: expected ‘}’ at end of input
src/ast.cpp: At global scope:
src/ast.cpp:2226: error: expected ‘}’ at end of input
src/units.hpp:11: warning: ‘Sass::PI’ defined but not used
make: *** [src/ast.o] Error 1
rake aborted!
Command failed with status (2): [make lib/libsass.so...]
/usr/local/rvm/gems/ruby-2.6.2/gems/sassc-2.0.1/lib/tasks/libsass.rb:31:in `block (2 levels) in <top (required)>'
/usr/local/rvm/gems/ruby-2.6.2/gems/sassc-2.0.1/lib/tasks/libsass.rb:13:in `block (3 levels) in <top (required)>'
/usr/local/rvm/gems/ruby-2.6.2/gems/sassc-2.0.1/lib/tasks/libsass.rb:12:in `block (2 levels) in <top (required)>'
Tasks: TOP => lib/libsass.so
(See full trace by running task with --trace)

rake failed, exit code 1

Gem files will remain installed in /usr/local/rvm/gems/ruby-2.6.2/gems/sassc-2.0.1 for inspection.
Results logged to /usr/local/rvm/gems/ruby-2.6.2/extensions/x86_64-linux/2.6.0/sassc-2.0.1/gem_make.out

经排查，是因为GCC的版本过低导致的。

按照这个步骤，检查下GCC版本，如果是同样的版本和报错，那么可以参考以下的解决方法：

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[root@localhost ~]# gcc --version | head -n1
gcc (GCC) 4.4.7 20120313 (Red Hat 4.4.7-23)

如果GCC是这个版本，那就安装新版本的的GCC：

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yum install centos-release-scl-rh
yum install devtoolset-7-gcc devtoolset-7-gcc-c++ devtoolset-7-binutils

安装好以后，再次配置GCC环境并检查版本：

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[root@localhost ~]# cat << _EOF_ > /etc/profile.d/devtoolset.sh
> #!/bin/bash
> source scl_source enable devtoolset-7
> _EOF_
[root@localhost ~]# 
[root@localhost ~]# gcc --version | head -n1
gcc (GCC) 4.4.7 20120313 (Red Hat 4.4.7-23)
[root@localhost ~]# cat /etc/profile.d/devtoolset.sh
#!/bin/bash
source scl_source enable devtoolset-7
[root@localhost ~]# source /etc/profile.d/devtoolset.sh
[root@localhost ~]# gcc --version | head -n1
gcc (GCC) 7.3.1 20180303 (Red Hat 7.3.1-5)

确认GCC配置好以后，再次执行bundle或者执行gem install sassc来安装即可。

编程 5 分钟 读完 (约 686 字)

随着现代浏览器性能的提升，前端工程师设计出的交互方式也多种多样。其中瀑布流方式滚动更新加载已经是一种常见的Web前端交互方式了。

然而在Rails中如何实现这样一种随着用户滚动页面就能自动追加内容到页面的方式呢？

有一些现成的Gem可以推荐，例如jquery-infinite-pages和will_paginate_infinite等。不过我觉得它们使用比较复杂，不如自己去实现一个。

本文既然提到最方便，自然是需要用一种最小化改动的方式来实现这样的功能。

具体如何实现，请往下看。

首先假设我们要实现瀑布流式动态更新的对象是Post(或者是Article、News或者其他)，第一步我们需要在Gemfile中加入以下两个Gem：

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gem 'will_paginate'
gem 'bootstrap-will_paginate'

然后执行bundle，接着去修改posts_controller.rb，修改其中的index方法：

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def index
  @posts = Post.all.paginate(:page => params[:page], :per_page => 10)

  respond_to do |format|
    format.html
    format.js
  end
end

这里由于我们增加了js的渲染格式，所以要去views/posts中添加一个index.js.erb模板文件，内容如下:

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$('#posts_list').append('<%= j render @posts %>');
<% if @posts.next_page %>
  $('.pagination').replaceWith('<%= j will_paginate @posts %>');
<% else %>
  $(window).off('scroll');
  $('.pagination').remove();
<% end %>

上面的代码通过js定位页面中的posts_list作为要追加元素的目标，所以我们稍微修改一下views/posts/index.html.erb，在其中加入posts_list元素：

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<div id="posts_list">
  <%= render @posts %>
</div>

<div id="infinite-scrolling">
  <%= will_paginate %>
</div>

在这段代码中，我们将@posts集合交给其他模板去渲染了，而这里暂时还没有用来渲染@posts的模板，所以要在views/posts中创建一个_post.html.erb模板文件，内容如下：

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<div>
<h3><%= post.title %></h3>
<p><%= post.content %></p>
<hr/>
</div>

就这么简单，用来输出标题和内容。

最后关键的一步，需要创建一个事件监听器来捕获页面的滚动变化，所以在assets/javascripts/posts.coffee中，加入以下代码：

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$(document).on "turbolinks:load", ->
  $(window).on 'scroll', ->
    more_posts_url = $('.pagination .next_page a').attr('href')
    if more_posts_url && $(window).scrollTop() > $(document).height() - $(window).height() - 60
      $('.pagination').html('<img src="/assets/ajax-loader.gif" alt="Loading..." title="Loading..." />')
      $.getScript more_posts_url
      return
    return

如此一来，就实现了通过ajax方式请求原来需要在下一页展现内容，并把内容追加到index.html的文章列表中，也就实现了瀑布流加载了。

一切修改好以后，重启Rails服务，在页面滚动一下试试吧。

本方法参考自https://www.sitepoint.com/infinite-scrolling-rails-basics/

编程 5 分钟 读完 (约 802 字)

CentOS6由于版本过老和源组织不当等原因，成功安装Python3和一些较新的依赖库是一件很幸运的事情。这里记录下遇到的报错和解决过程。
按照惯例，先记录一下报错内容，方便搜索引擎索引：

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[root@localhost ~]# pip3 install --upgrade pip
pip is configured with locations that require TLS/SSL, however the ssl module in Python is not available.
Retrying (Retry(total=4, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError("Can't connect to HTTPS URL because the SSL module is not available.")': /simple/pip/
Retrying (Retry(total=3, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError("Can't connect to HTTPS URL because the SSL module is not available.")': /simple/pip/
Retrying (Retry(total=2, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError("Can't connect to HTTPS URL because the SSL module is not available.")': /simple/pip/
Retrying (Retry(total=1, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError("Can't connect to HTTPS URL because the SSL module is not available.")': /simple/pip/
Retrying (Retry(total=0, connect=None, read=None, redirect=None, status=None)) after connection broken by 'SSLError("Can't connect to HTTPS URL because the SSL module is not available.")': /simple/pip/
Could not fetch URL https://pypi.org/simple/pip/: There was a problem confirming the ssl certificate: HTTPSConnectionPool(host='pypi.org', port=443): Max retries exceeded with url: /simple/pip/ (Caused by SSLError("Can't connect to HTTPS URL because the SSL module is not available.")) - skipping
Requirement already up-to-date: pip in /usr/local/lib/python3.7/site-packages (19.0.3)
pip is configured with locations that require TLS/SSL, however the ssl module in Python is not available.
Could not fetch URL https://pypi.org/simple/pip/: There was a problem confirming the ssl certificate: HTTPSConnectionPool(host='pypi.org', port=443): Max retries exceeded with url: /simple/pip/ (Caused by SSLError("Can't connect to HTTPS URL because the SSL module is not available.")) - skipping

解决方法：

1.编译安装OpenSSL 1.0.2j版本并配置环境变量

下载OpenSSL源码包：

wget http://www.openssl.org/source/openssl-1.0.2j.tar.gz

解压缩，编译安装：

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tar -zxvf openssl-1.0.2j.tar.gz
cd openssl-1.0.2j
./config --prefix=/usr/local/openssl-1.0.2j shared zlib
make && make install

2.编译安装Python3,使用自定义的OpenSSL

下载Python3.7.3源码包：

wget https://www.python.org/ftp/python/3.7.3/Python-3.7.3.tgz

解压缩，编译安装：

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tar -zxvf Python-3.7.3.tgz
cd Python-3.7.3
./configure

在这一步之后，先不要着急运行make命令。先修改Modules/Setup文件：

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# Socket module helper for socket(2)
#_socket socketmodule.c

# Socket module helper for SSL support; you must comment out the other
# socket line above, and possibly edit the SSL variable:
SSL=/usr/local/openssl-1.0.2j/      #取消这一行的注释，并将原来的/usr/local/ssl改为/usr/local/openssl-1.0.2j/
_ssl _ssl.c \     #取消这一行的注释
    -DUSE_SSL -I$(SSL)/include -I$(SSL)/include/openssl \      #取消这一行的注释
    -L$(SSL)/lib -lssl -lcrypto      #取消这一行的注释

# The crypt module is now disabled by default because it breaks builds
# on many systems (where -lcrypt is needed), e.g. Linux (I believe).

#_crypt _cryptmodule.c # -lcrypt    # crypt(3); needs -lcrypt on some systems

修改完成以后，还需要创建两个指向动态链接库的软链接文件：

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ln -s /usr/local/openssl-1.0.2j/lib/libssl.so.1.0.0 /usr/lib64/libssl.so.1.0.0
ln -s /usr/local/openssl-1.0.2j/lib/libcrypto.so.1.0.0 /usr/lib64/libcrypto.so.1.0.0

最后编译并安装：

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make && make install

安装完成以后，再次运行pip3 install --upgrade pip，可以看到原先SSL连接报错的问题已经解决：

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[root@localhost Python-3.7.3]# pip3 install --upgrade pip
Collecting pip
  Using cached https://files.pythonhosted.org/packages/5c/e0/be401c003291b56efc55aeba6a80ab790d3d4cece2778288d65323009420/pip-19.1.1-py2.py3-none-any.whl
Installing collected packages: pip
  Found existing installation: pip 19.0.3
    Uninstalling pip-19.0.3:
      Successfully uninstalled pip-19.0.3
Successfully installed pip-19.1.1

编程 3 分钟 读完 (约 496 字)

在以root用户运行Puppeteer程序时，遇到一些错误，这里记录下解决的过程。
首先提示一个X11错误，这是因为我在服务器上运行Chrome，而服务器没有安装桌面环境导致的。
安装以下依赖项即可，以Debian系统为例：

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apt-get install gconf-service libasound2 libatk1.0-0 libc6 libcairo2 libcups2 libdbus-1-3 libexpat1 libfontconfig1 libgcc1 libgconf-2-4 libgdk-pixbuf2.0-0 libglib2.0-0 libgtk-3-0 libnspr4 libpango-1.0-0 libpangocairo-1.0-0 libstdc++6 libx11-6 libx11-xcb1 libxcb1 libxcomposite1 libxcursor1 libxdamage1 libxext6 libxfixes3 libxi6 libxrandr2 libxrender1 libxss1 libxtst6 ca-certificates fonts-liberation libappindicator1 libnss3 lsb-release xdg-utils wget

接着就是报了一个sandbox错误，报错内容是这样的：

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(node:4963) UnhandledPromiseRejectionWarning: Error: Failed to launch chrome!
[0428/104254.469304:ERROR:zygote_host_impl_linux.cc(89)] Running as root without --no-sandbox is not supported. See https://crbug.com/638180.


TROUBLESHOOTING: https://github.com/GoogleChrome/puppeteer/blob/master/docs/troubleshooting.md

    at onClose (/root/monkey/node_modules/puppeteer/lib/Launcher.js:342:14)
    at Interface.helper.addEventListener (/root/monkey/node_modules/puppeteer/lib/Launcher.js:331:50)
    at emitNone (events.js:111:20)
    at Interface.emit (events.js:208:7)
    at Interface.close (readline.js:370:8)
    at Socket.onend (readline.js:149:10)
    at emitNone (events.js:111:20)
    at Socket.emit (events.js:208:7)
    at endReadableNT (_stream_readable.js:1064:12)
    at _combinedTickCallback (internal/process/next_tick.js:138:11)
(node:4963) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 1)
(node:4963) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

不了解具体的含义，但是从sandbox来看，应该是和Chrome的安全沙箱有关，单纯的想解决这个问题，只需要在代码中加入--no-sandbox启动Chrome的参数即可。

Example:

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const puppeteer = require('puppeteer');
(async () => {
  const browser = await puppeteer.launch({args: ['--no-sandbox']});
  const page = await browser.newPage();
  await page.goto("https://www.baidu.com");
  await browser.close();
})()

Tips：

但是这样做可能会造成一些风险，主要是Chrome的sandbox会多一些安全特性（我理解的），如果是将Node的代码作为生产环境运行在产品中，还是需要谨慎一些的，确保请求的站点安全可信（最好不信）。

编程 7 分钟 读完 (约 1070 字)

找Rails靠谱的编辑器是不是找了好久了？别找了，就用Simditor吧。
要如何在Rails中完美集成这样一个简洁大气又好用的编辑器呢？我们都知道，在高版本的Rails中使用CoffeeScript已经成为了一种习惯。所以本文将以CoffeeScript作为粘合剂来演示如何集成Simditor编辑器到Rails应用中，同时采用Rails原生的ActiveStorage作为上传支撑。

事先声明下我的环境配置：
Ruby: ruby 2.4.1p111 (2017-03-22 revision 58053) [x86_64-linux]
Rails: Rails 5.2.2

1. 准备工作

首先我们新建一个Rails项目，在命令行中，运行rails new Demo，待工程创建好以后我们进入Demo目录，新建一个脚手架。这里我们就以Article作为脚手架的名字，运行rails g scaffold Article title:string content:text

创建好之后，运行rails db:migrate，迁移数据库

此时，将simeditor添加到Gemfile中。修改Gemfile，加入以下内容并执行bundle（simditor需要jquery的支持）。

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gem 'jquery-rails'
gem 'simditor'

并在app/assets/javascripts/application.js中加入simditor的引用，此处需要注意，下面两行代码需要添加在//= require_tree这行代码之前，否则会出错。

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//= require jquery
//= require simditor
//= require_tree .

同时需要在app/assets/stylesheets/application.css中加入simditor的样式文件：

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*= require simditor

启动Rails应用，在浏览器中访问/articles/new，此时的界面如下：

到这里，准备工作就完成了。

2. 修改编辑框，集成Simditor

按照Rails的命名惯例，此处编辑框textarea的ID是article_content，我们的CoffeeScript脚本中，则需用选择器来绑定这个text_area。

修改app/assets/javascripts/article.coffee，加入以下内容：

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$(document).on "turbolinks:load", ->
    editor = new Simditor(
        textarea: $('#article_content')
        toolbar: [ 'bold', 'italic', 'underline', 'strikethrough', 'color',
            'code', 'blockquote', 'link', 'image', 'ol', 'ul', 'table', 'indent','outdent','alignment']
        pasteImage: true,
        fileKey: 'file',
        upload: {
            url: '/images',
            params: {"content":"image"},
            connectionCount: 3,
            leaveConfirm: '有图片正在上传，确定要离开?'
    })

再次在浏览器中访问/articles/new，界面变成了这样：

此时Simditor已经集成到了应用中了。

3. 使用ActiveStorage配置上传功能

ActiveStorage是Rails 5.2 以后推出的用于专门管理Web上传内容的组件，和ActiveRecord一样，是一个很方便同时又很强大的Rails Web开发组件。想要集成基于ActiveStorage的上传功能，首先要在我们的应用中安装ActiveStorage：

运行rails active_storage:install然后再运行rails db:migrate:

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root@debian:~/Demo# rails active_storage:install
Copied migration 20190327123314_create_active_storage_tables.active_storage.rb from active_storage
root@debian:~/Demo# rails db:migrate
== 20190327123314 CreateActiveStorageTables: migrating ========================
-- create_table(:active_storage_blobs)
   -> 0.0050s
-- create_table(:active_storage_attachments)
   -> 0.0027s
== 20190327123314 CreateActiveStorageTables: migrated (0.0086s) ===============

迁移完成以后，我们新建一个Upload控制器，使用rails g controller Upload命令生成它。修改Upload控制器代码，位于app/controllers/upload_controller.rb，添加一个upload方法：

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#app/controllers/upload_controller.rb
class UploadController < ApplicationController

  skip_before_action :verify_authenticity_token, :only => [:upload]

  def upload

    puts "*"*64
    puts params

    blob = ActiveStorage::Blob.create_after_upload!(
      io: params[:image],
      filename: params[:image].original_filename,
      content_type: params[:image].content_type
    )

    if blob.save
      success = true
      msg = 'upload success'
    else
      success = false
      msg = "upload error"
    end

    render json: { :success=> success, :msg=>msg, :file_path=> rails_blob_path(blob) }

  end

end


修改路由配置文件，指定我们的上传路由：

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#config/routes.rb
Rails.application.routes.draw do
  post 'images/upload' => 'upload#upload'
  resources :articles
  root to: 'articles#index'
  # For details on the DSL available within this file, see http://guides.rubyonrails.org/routing.html
end

还要稍微修改一下我们的articles.coffee文件，改一下其中的上传路径和参数，用于Ajax提交图片：

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//app/assets/javascripts/articles.coffee
$(document).on "turbolinks:load", ->
    editor = new Simditor(
        textarea: $('#article_content')
        toolbar: [ 'bold', 'italic', 'underline', 'strikethrough', 'color',
            'code', 'blockquote', 'link', 'image', 'ol', 'ul', 'table', 'indent','outdent','alignment']
        pasteImage: true,
        fileKey: 'file',
        upload: {
            url: '/images/upload', //<==上传接口
            fileKey: 'image', //<=参数名称
            params: {"content":"image"},
            connectionCount: 3,
            leaveConfirm: '有图片正在上传，确定要离开?'
    })

至此，已经可以在页面中正常地上传文件了，也可以直接从粘贴板复制文件，Simditor会自动上传文件：

本文涉及到的代码已经上传到Github，仓库链接：https://github.com/Chorder/RailsSimditorActiveStorageDemo

编程 6 分钟 读完 (约 971 字)

最近睡前把《Ruby元编程》作为枕边书，复习一些元编程技巧。顺手整理记录下这些技巧的同时，也为了这门语言能更广泛地传播，希望有更多的人喜欢Ruby这个神器。

一切都是对象

来到Ruby的世界，请你首先不要被这一切搞晕，实际上这些反而让Ruby的对象模型概念变得更加清晰。一切都是对象，对象是一个类，类也是一个对象。而实际上类是一个带有特殊功能的模块。

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2.5.1 :001 > Class.superclass
 => Module
2.5.1 :002 > Module.superclass
 => Object
2.5.1 :003 > Object.superclass
 => BasicObject
2.5.1 :004 > BasicObject.superclass
 => nil
2.5.1 :005 > Kernel.class
=> Module

模块的超类是BasicObject，BasicObject才是Ruby类系统的根。BasicObject派生了Objce和Kernel，Object又派生出了Module，Module派生出Class。
这像不像道德经里所说的“道生一，一生二，二生三，三生万物”？ 再说下去更迷糊了，去Ruby的世界里自己领悟吧。Ruby诞生自亚洲，一直觉得它是一门充满东方哲学的编程语言。

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2.5.1 :001 > Class.ancestors
 => [Class, Module, Object, Kernel, BasicObject]
2.5.1 :002 > Class.superclass
 => Module
2.5.1 :003 > Module.ancestors
 => [Module, Object, Kernel, BasicObject]
2.5.1 :004 > Module.superclass
 => Object
2.5.1 :005 > Object.ancestors
 => [Object, Kernel, BasicObject]
2.5.1 :006 > Object.superclass
 => BasicObject
2.5.1 :007 > BasicObject.superclass
 => nil
2.5.1 :008 > Kernel.ancestors
 => [Kernel]
2.5.1 :009 > BasicObject.ancestors
=> [BasicObject]

猴子补丁(Monkey Patch)

在元编程的所有技巧中，首先需要了解的就是Ruby的“猴子补丁”，这是一种打开类的技巧。不同于其他面向对象语言，Ruby的任何类都可以在运行态打“补丁”的，称之为Monkey Patch。

例如，对字符类String，可以在任何地方打开这个类，对它添加一些方法：

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2.5.1 :001 > class String
2.5.1 :002?>   def test_method
2.5.1 :003?>     return self+"AAA"
2.5.1 :004?>   end
2.5.1 :005?> end
 => :test_method
2.5.1 :006 > s="aaa"
 => "aaa"
2.5.1 :007 > s.class
 => String
2.5.1 :008 > s.test_method
 => "aaaAAA"
2.5.1 :009 >

在上面的操作中，我们可以看到，对于Ruby的内置类String，我们为其添加了test_method方法，在下文中，任何的String对象便具有了新添加的这个方法，这就是Ruby打开类的魔术。

你甚至可以对内核模块Kernel打一个Monkey Patch，让你的方法在下文中得到全局支持：

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2.5.1 :001 > test
Traceback (most recent call last):
        3: from /home/chorder/.rvm/rubies/ruby-2.5.1/bin/irb:11:in <main>
        2: from (irb):1
        1: from (irb):1:in test
ArgumentError (wrong number of arguments (given 0, expected 2..3))
2.5.1 :002 > module Kernel
2.5.1 :003?>   def test
2.5.1 :004?>     puts "OK"
2.5.1 :005?>   end
2.5.1 :006?> end
 => :test
2.5.1 :007 > test
OK
 => nil
2.5.1 :008 >

不同的是，Kernel是一个模块，需要用module关键字来打开。test方法一开始是不存在的，把它作为“补丁”加入到Kernel模块以后，就可以在下文调用了。

Monkey Patch在有些编程语言里是个贬义词，但在Ruby里，它是一个很实用的功能。

细化(refine)

如你所见，Ruby打开类的作用是如此神奇，以至于Monkey Patch一不小心可能会引发一些大的问题。因此有时候需要配合类的细化功能一起使用。

细化的用法如下：

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2.5.1 :001 > module Refine
2.5.1 :002?>   refine String do
2.5.1 :003 >       def test
2.5.1 :004?>         return self+"TEST"
2.5.1 :005?>       end
2.5.1 :006?>     end
2.5.1 :007?>   end
 => #<refinement:String@Refine>
2.5.1 :008 > "AAA".test
Traceback (most recent call last):
        2: from /home/chorder/.rvm/rubies/ruby-2.5.1/bin/irb:11:in <main>
        1: from (irb):8
NoMethodError (private method test called for "AAA":String)
2.5.1 :009 > module Test
2.5.1 :010?>   using Refine
2.5.1 :011?>   "AAA".test
2.5.1 :012?>   end
 => "AAATEST"
2.5.1 :013 >

在一个模块中使用refine关键字定义细化之后，在另一个模块中使用using关键字引入这个用于定义细化的模块，细化定义的作用于就只限于调用细化模块的模块内部。

命名空间(Name Space)

在Ruby中，使用::标识引入不同作用域中的类和模块，用于界定类和模块，防止命名冲突，也让源代码的结构更加清晰。

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2.5.1 :001 > module A
2.5.1 :002?>     module B
2.5.1 :003?>         class C
2.5.1 :004?>             D="Constant"
2.5.1 :005?>           end
2.5.1 :006?>       end
2.5.1 :007?>   end
 => "Constant"
2.5.1 :008 >
2.5.1 :009 > A::B::C::D
 => "Constant"
2.5.1 :010 >

编程 3 分钟 读完 (约 419 字)

在Debian系Linux中，用于标识应用的启动文件.desktop file是位于/usr/share/applications目录下的，Gnome会将这些文件在菜单中展示为启动图标，也可以固定在docker bar。

打开/usr/share/applications，可以看到有很多的.desktop文件，每一个文件就对应菜单中的一个启动图标。

如何手动编辑和制作这样一个.desktop文件呢，这里以IDEA集成开发环境为例。
我的IDEA安装在/opt/idea-IC-182.4505.22/目录，IDEA的启动脚本是/opt/idea-IC-182.4505.22/bin/idea.sh。打开/opt/idea-IC-182.4505.22/目录，还可以看到IDEA的图标文件/opt/idea-IC-182.4505.22/bin/idea.png。

所以我们在/opt/idea-IC-182.4505.22/目录下创建IDEA.desktop文件，内容如下：

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[Desktop Entry]
Name=IDEA
Encoding=UTF-8
Exec=/opt/idea-IC-182.4505.22/bin/idea.sh
Icon=/opt/idea-IC-182.4505.22/bin/idea.png
StartupNotify=false
Terminal=false
Type=Application
#Categories=

再将IDEA.desktop通过软链接添加到/usr/share/applications目录即可。

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ls -s /opt/idea-IC-182.4505.22/IDEA.desktop /usr/share/applications/IDEA.desktop

再次打开菜单，即可看见创建的启动图标。如果看不到，可以先注销，再重新登录即可。

再分享两个常用的.desktop文件：

burpsuite(可用在kali上)

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[Desktop Entry]
Name=burpsuite-pro-2
Encoding=UTF-8
Exec=sh -c "java -Xbootclasspath/p:/opt/burpsuite_pro_2.0.09/burp-loader-keygen.jar -jar /opt/burpsuite_pro_2.0.09/burpsuite_pro_v2.0.09beta.jar"
Icon=kali-burpsuite.png
StartupNotify=false
Terminal=false
Type=Application
#Categories=03-webapp-analysis;03-06-web-application-proxies;
X-Kali-Package=burpsuite

JD-GUI

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[Desktop Entry]
Name=JD-GUI
Encoding=UTF-8
Exec=sh -c "java -jar /opt/jd-gui-1.4.0/jd-gui-1.4.0.jar"
Icon=/usr/share/icons/hicolor/128x128/apps/jd-gui.png
StartupNotify=false
Terminal=false
Type=Application
#Categories=03-webapp-analysis;03-06-web-application-proxies;
Name[en_US]=JD-GUI

编程 2 分钟 读完 (约 266 字)

jar命令是用来将java编译产生的.class文件打包成jar包的工具。
Jar包可以方便地对外发布，甚至就像exe一样易于使用。

这里以一个工具类JarParser为例，这个示例程序是用来遍历Jar包中的类的。

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/*JarParser.java*/
/*源码转载自：https://blog.csdn.net/lululove19870526/article/details/78837119*/

import java.util.Enumeration;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;

public class JarParser {

    public static void main(String args[]) {
        if(args.length<1) System.exit(0);
        String jar = args[0];
        try {
            JarFile jarFile = new JarFile(jar);
            Enumeration enu = jarFile.entries();
            while (enu.hasMoreElements()) {
                JarEntry jarEntry = (JarEntry) enu.nextElement();
                String name = jarEntry.getName();
                if (name.endsWith(".class"))
                  System.out.println("Class: "+name.replace('/','.'));
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}


使用javac命令编译这个Java文件：javac JarParser.java

接着创建一个文本文件，这个文件用来作为jar包中的MANIFEST.MF描述文件。

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echo Main-Class: JarParser > test.mf

这句Main-Class的作用是指明Jar包的入口类。

最后使用jar命令打包：

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jar cvfm JarParser.jar test.mf JarParser.class

生成的jar包使用java -jar命令运行。

编程 3 分钟 读完 (约 469 字)

系统环境：

  • Ruby: ruby 2.5.1p57 (2018-03-29 revision 63029) [x86_64-linux]
  • Rails: Rails 5.2.2
  • Gem: 2.7.7
  • SQLite: sqlite3 (1.4.0, 1.3.13)

今天在基于上面的环境使用Rails新建项目的时候，报了一个ActiveRecord::ConnectionNotEstablished错误。
根据排查，是由于SQLite3 gem版本问题导致的。
具体的报错内容如下：

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Puma caught this error: Error loading the 'sqlite3' Active Record adapter. Missing a gem it depends on? can't activate sqlite3 (~> 1.3.6), already activated sqlite3-1.4.0. Make sure all dependencies are added to Gemfile. (LoadError)

页面报错如下：

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ActiveRecord::ConnectionNotEstablished
No connection pool with 'primary' found.

后来找到了解决方法，修改Gemfile，将sqlite3的版本降级到1.4.0以下即可。
修改Gemfile：

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source 'https://rubygems.org'
git_source(:github) { |repo| "https://github.com/#{repo}.git" }

ruby '2.5.1'

# Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
gem 'rails', '~> 5.2.2'
# Use sqlite3 as the database for Active Record
gem 'sqlite3', '< 1.4.0'  # <<修改这里，将sqlite3版本设定为小于1.4.0
# Use Puma as the app server
gem 'puma', '~> 3.11'
# Use SCSS for stylesheets
gem 'sass-rails', '~> 5.0'
# Use Uglifier as compressor for JavaScript assets
gem 'uglifier', '>= 1.3.0'
# See https://github.com/rails/execjs#readme for more supported runtimes
# gem 'mini_racer', platforms: :ruby

# Use CoffeeScript for .coffee assets and views
gem 'coffee-rails', '~> 4.2'
# Turbolinks makes navigating your web application faster. Read more: https://github.com/turbolinks/turbolinks
gem 'turbolinks', '~> 5'
# Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder
gem 'jbuilder', '~> 2.5'
# Use Redis adapter to run Action Cable in production
# gem 'redis', '~> 4.0'
# Use ActiveModel has_secure_password
# gem 'bcrypt', '~> 3.1.7'

# Use ActiveStorage variant
# gem 'mini_magick', '~> 4.8'

# Use Capistrano for deployment
# gem 'capistrano-rails', group: :development

# Reduces boot times through caching; required in config/boot.rb
gem 'bootsnap', '>= 1.1.0', require: false

group :development, :test do
  # Call 'byebug' anywhere in the code to stop execution and get a debugger console
  gem 'byebug', platforms: [:mri, :mingw, :x64_mingw]
end

group :development do
  # Access an interactive console on exception pages or by calling 'console' anywhere in the code.
  gem 'web-console', '>= 3.3.0'
  gem 'listen', '>= 3.0.5', '< 3.2'
  # Spring speeds up development by keeping your application running in the background. Read more: https://github.com/rails/spring
  gem 'spring'
  gem 'spring-watcher-listen', '~> 2.0.0'
end

group :test do
  # Adds support for Capybara system testing and selenium driver
  gem 'capybara', '>= 2.15'
  gem 'selenium-webdriver'
  # Easy installation and use of chromedriver to run system tests with Chrome
  gem 'chromedriver-helper'
end

# Windows does not include zoneinfo files, so bundle the tzinfo-data gem
gem 'tzinfo-data', platforms: [:mingw, :mswin, :x64_mingw, :jruby]


修改完后执行bundle即可。

编程 2 分钟 读完 (约 321 字)

你在MongoDB启动时也遇到以下警告吗？

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WARNING: You are running on a NUMA machine.
We suggest launching mongod like this to avoid performance problems:
numactl –interleave=all mongod [other options]

这是当MongoDB运行在非统一内存访问架构 NUMA(Non Uniform Memory Access Architecture)下产生的性能告警。
关于NUMA是什么，可以参考这篇文章：Non-uniform memory access

这里主要提一下在CentOS 7系统、NUMA架构服务器中上述告警该如何消除。

首先需要使用numactl这个命令，而这条命令服务器中默认是没有的，在支持NUMA架构的CentOS7服务器中，可以运行yum install numactl来安装它。

接着关闭MongoDB服务：
systemctl stop mongod

disable掉MongoDB服务的自动启动：
systemctl disable mongod

使用numactl来启动MongoDB：
numactl --interleave=all mongod --config /etc/mongod.conf

如果想要开机自动使用numactl启动MongoDB，将上述命令写到开机启动的脚本文件中即可。

笔者尝试修改mongod.service服务描述中的ExecStart选项，尝试将numctl作为mongod服务的执行体时报了很多错，如果你有相关的解决方法，欢迎来信或在评论里探讨。

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