红宝石全局方法上轨型号 [英] global methods in ruby on rails models

问题描述

我在我所有的模型的方法是这样的：

I have methods in all of my models that look like this:

def formatted_start_date
  start_date ? start_date.to_s(:date) : nil
end

我想有一些东西，在每个模型自动写一个这样的方法对于每个时间字段，什么是做到这一点的最好方法是什么？

I would like to have something that automatically writes a method like this for each datetime field in each model, what's the best way to do this?

-C

推荐答案

我刚要回答这个问题，因为这一切是一个有趣的Ruby锻炼; Tibial。

I just had to answer this, cos it's a fun Ruby excercise.

添加方法，一类是可以做到的方法很多，但最巧妙的方法之一是使用了Ruby的反思和评价功能。

Adding methods to a class can be done many ways, but one of the neatest ways is to use some of the reflection and evaluation features of Ruby.

在你的lib文件夹中的lib / date_methods.rb创建这个文件

Create this file in your lib folder as lib/date_methods.rb

module DateMethods

  def self.included(klass)

    # get all dates
    # Loop through the class's column names
    # then determine if each column is of the :date type.
    fields = klass.column_names.select do |k| 
                  klass.columns_hash[k].type == :date
                end


    # for each of the fields we'll use class_eval to
    # define the methods.
    fields.each do |field|
      klass.class_eval <<-EOF
        def formatted_#{field}
          #{field} ? #{field}.to_s(:date) : nil
        end

      EOF
    end
  end
end

现在只是其包含到任何需要它的模型

Now just include it into any models that need it

 class CourseSection < ActiveRecord::Base
   include DateMethods
 end

在包括在内，该模块将看任何日期列，并生成formatted_方法给你。

When included, the module will look at any date columns and generate the formatted_ methods for you.

了解如何红宝石东西的作品。这是一个很大的乐趣。

Learn how this Ruby stuff works. It's a lot of fun.

这是说，你要问自己，如果这是必要的。我不认为这是个人的，但再一次，很好玩写。

That said, you have to ask yourself if this is necessary. I don't think it is personally, but again, it was fun to write.

-b -

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