How to be an independent Ruby programmer_问答_开发者

I am tired of asking unanswered questions when using many outdated plugins / gems, and sometimes they don't really work how I really wanted.

So my question is simple:

If I was a PHP programmer, and Rails was m开发者_开发知识库y first framework, what do I need to learn next so I can depend on myself when working with troublesome plugins or code snippets or tutorials?

I used to be quite good with an (rather silly now that I know MVC) e-commerce system in PHP, and normally I would just go ahead and read out the plugin's code to find out what it does, but apparently doing so is extremely hard in Ruby on Rails, should I keep doing it, or am I going the right track? (I did learn by the way, but in very slow pace compared when I was still using PHP and that "e-commerce framework")

This is like a generic programming question for me. If you have any troubles with some Rails plugin, you can always debug its code with a bunch of hardcore or easy methods, try to understand and fix the error. The question is, which methods should you use in particular situations.

I will give you a little example. When you are debugging your Rails application, always check either logs/production.log or logs/development.log (depending on mode you're working) for errors of any kinds. Every error in Ruby/Rails is represented by a huge stack-trace that you should read from top to bottom. Like this one:

Processing CommentsController#create (for ***.***.***.171 at 2010-08-27 03:31:29) [POST]
  Parameters: {"authenticity_token"=>"[STRIPPED]"}, "last_comment_id"=>"0", "original_controller"=>"projects", "thread"=>"true", "thread_id"=>"Conversation_31", "commit"=>"Save", "_"=>"", "controller"=>"comments", "action"=>"create", "conversation_id"=>"31"}
Sent mail to email@email.com

ArgumentError (invalid byte sequence in UTF-8):
  /usr/lib/ruby/1.9.1/net/protocol.rb:294:in `slice!'
  /usr/lib/ruby/1.9.1/net/protocol.rb:294:in `each_crlf_line'
  /usr/lib/ruby/1.9.1/net/protocol.rb:236:in `write_message_0'
  /usr/lib/ruby/1.9.1/net/protocol.rb:250:in `block (2 levels) in write_message'
  /usr/lib/ruby/1.9.1/net/protocol.rb:280:in `using_each_crlf_line'
  /usr/lib/ruby/1.9.1/net/protocol.rb:250:in `block in write_message'
  /usr/lib/ruby/1.9.1/net/protocol.rb:169:in `writing'
  /usr/lib/ruby/1.9.1/net/protocol.rb:249:in `write_message'
  /usr/lib/ruby/1.9.1/net/smtp.rb:878:in `block in data'
  /usr/lib/ruby/1.9.1/net/smtp.rb:921:in `critical'
  /usr/lib/ruby/1.9.1/net/smtp.rb:875:in `data'
  /usr/lib/ruby/1.9.1/net/smtp.rb:655:in `send_message'
  actionmailer (2.3.8) lib/action_mailer/base.rb:684:in `block in perform_delivery_smtp'
  /usr/lib/ruby/1.9.1/net/smtp.rb:526:in `start'
  actionmailer (2.3.8) lib/action_mailer/base.rb:682:in `perform_delivery_smtp'
  actionmailer (2.3.8) lib/action_mailer/base.rb:523:in `deliver!'
  actionmailer (2.3.8) lib/action_mailer/base.rb:395:in `method_missing'
  app/models/emailer.rb:89:in `send_with_language'
  app/models/conversation.rb:51:in `block in notify_new_comment'
  app/models/conversation.rb:47:in `each'
  app/models/conversation.rb:47:in `notify_new_comment'
  ...

Here we are! The line ArgumentError (invalid byte sequence in UTF-8):, on the very top of this trace, always tells us the error type. It's an argument error!

After that, look at the next line: /usr/lib/ruby/1.9.1/net/protocol.rb:294:in 'slice!'. It tells where the exception (ArgumentError) was raised in the following format:

 /path/to/file/:line:in `method_name'`

Let's open that neglectful file and find the source around that line:

def each_crlf_line(src)
    buffer_filling(@wbuf, src) do
        while line = @wbuf.slice!(/\A.*(?:\n|\r\n|\r(?!\z))/n)
            yield line.chomp("\n") + "\r\n"
        end
    end
end

The error is on the following line:

while line = @wbuf.slice!(/\A.*(?:\n|\r\n|\r(?!\z))/n)

From this point we know where the error is and only need to fix it, but this process is out of scope of my short story. I just wanted to show you how to work with errors in Rails.

You should keep reading plugin code.

If it is extremely hard, you may become extremely good at it.

Go watch the Yehuda Katz video at on the homepage of railsconf.blip.tv. He's now one of the core rails developers and discusses how he got into it.