blocks|key|1105247|text|您可以简单地扩展类并简单地使用继承。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1105248|class+AbstractModel+<+ActiveRecord::Base++
++self.abstract_class+=+true
end

class+Foo+<+AbstractModel
end

class+Bar+<+AbstractModel
end|code-block|syntax|javascript|1105249|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

You can just extend the class and simply use inheritance. 

<pre><code>class AbstractModel &lt; ActiveRecord::Base 
 self.abstract_class = true
end

class Foo &lt; AbstractModel
end

class Bar &lt; AbstractModel
end
</code></pre>

blocks|key|1105287|text|您也可以使用ActiveSupport::Concern，更像是Rails的核心习惯用法：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1105288|module+MyExtension
++extend+ActiveSupport::Concern

++def+foo
++end

++module+ClassMethods
++++def+bar
++++end
++end
end

ActiveRecord::Base.send(:include,+MyExtension)|code-block|syntax|javascript|1105289|根据@daniel的评论进行编辑|1105290|然后，您的所有模型都将包含方法foo作为实例方法，并将ClassMethods中的方法包含为类方法。例如，在FooBar+<+ActiveRecord::Base上，您将拥有：FooBar.bar和FooBar#foo|1105291|http://api.rubyonrails.org/classes/ActiveSupport/Concern.html|1105292|entityMap|0|LINK|mutability|MUTABLE|url^0|6|M|0|0|0|F|3|R|C|1I|R|2G|A|2R|A|0|0|1P|0|0^^$0|@$1|2|3|4|5|6|7|X|8|@$9|Y|A|Z|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|10|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|11|8|@]|D|@]|E|$]]|$1|M|3|N|5|6|7|12|8|@$9|13|A|14|B|C]|$9|15|A|16|B|C]|$9|17|A|18|B|C]|$9|19|A|1A|B|C]|$9|1B|A|1C|B|C]]|D|@]|E|$]]|$1|O|3|P|5|6|7|1D|8|@]|D|@$9|1E|A|1F|1|1G]]|E|$]]|$1|Q|3|-4|5|6|7|1H|8|@]|D|@]|E|$]]]|R|$S|$5|T|U|V|E|$W|P]]]]

You can also use <code>ActiveSupport::Concern</code> and be more Rails core idiomatic like:

<pre><code>module MyExtension
 extend ActiveSupport::Concern

 def foo
 end

 module ClassMethods
 def bar
 end
 end
end

ActiveRecord::Base.send(:include, MyExtension)
</code></pre>

[Edit] following the comment from @daniel

Then all your models will have the method <code>foo</code> included as an instance method and the methods in <code>ClassMethods</code> included as class methods. E.g. on a <code>FooBar &lt; ActiveRecord::Base</code> you will have: <code>FooBar.bar</code> and <code>FooBar#foo</code>

<a href="http://api.rubyonrails.org/classes/ActiveSupport/Concern.html">http://api.rubyonrails.org/classes/ActiveSupport/Concern.html</a>

blocks|key|1320345|text|Rails5提供了一个扩展ActiveRecord::Base的内置机制。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1320346|这是通过提供额外的层来实现的：|1320347|#+app/models/application_record.rb
class+ApplicationRecord+<+ActiveRecord::Base
++self.abstract_class+=+true
++#+put+your+extensions+here
end|code-block|syntax|javascript|1320348|所有的模型都是从这个模型继承过来的：|1320349|class+Post+<+ApplicationRecord
end|1320350|例如，参见this+blogpost。|1320351|entityMap|0|LINK|mutability|MUTABLE|url|http://blog.bigbinary.com/2015/12/28/application-record-in-rails-5.html^0|D|I|0|0|0|0|0|5|D|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@$9|11|A|12|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|13|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|14|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|15|8|@]|D|@]|E|$]]|$1|O|3|P|5|J|7|16|8|@]|D|@]|E|$K|L]]|$1|Q|3|R|5|6|7|17|8|@]|D|@$9|18|A|19|1|1A]]|E|$]]|$1|S|3|-4|5|6|7|1B|8|@]|D|@]|E|$]]]|T|$U|$5|V|W|X|E|$Y|Z]]]]

Rails 5 provides a built-in mechanism for extending <code>ActiveRecord::Base</code>.

This is achieved by providing additional layer:

<pre class="lang-rb prettyprint-override"><code># app/models/application_record.rb
class ApplicationRecord &lt; ActiveRecord::Base
 self.abstract_class = true
 # put your extensions here
end
</code></pre>

and all models inherit from that one:

<pre class="lang-rb prettyprint-override"><code>class Post &lt; ApplicationRecord
end
</code></pre>

See e.g. <a href="http://blog.bigbinary.com/2015/12/28/application-record-in-rails-5.html" rel="noreferrer">this blogpost</a>.

blocks|key|1320372|text|在Rails5中，所有模型都继承自ApplicationRecord+&它提供了很好的方式来包含或扩展其他扩展库。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1320373|#+app/models/concerns/special_methods.rb
module+SpecialMethods
++extend+ActiveSupport::Concern

++scope+:this_month,+->+{+
++++where("date_trunc('month',created_at)+=+date_trunc('month',now())")
++}

++def+foo
++++#+Code
++end
end|code-block|syntax|javascript|1320374|假设特殊方法模块需要在所有模型中都可用，请将其包含在application_record.rb文件中。如果我们想要将其应用于一组特定的模型，则将其包含在相应的模型类中。|1320375|#+app/models/application_record.rb
class+ApplicationRecord+<+ActiveRecord::Base
++self.abstract_class+=+true
++include+SpecialMethods
end

#+app/models/user.rb
class+User+<+ApplicationRecord
++include+SpecialMethods

++#+Code
end|1320376|如果希望将模块中的方法定义为类方法，请将该模块扩展为ApplicationRecord。|1320377|#+app/models/application_record.rb
class+ApplicationRecord+<+ActiveRecord::Base
++self.abstract_class+=+true
++extend+SpecialMethods
end|1320378|希望它能帮助其他人！|1320379|entityMap^0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|W|8|@]|9|@]|A|$]]|$1|M|3|N|5|D|7|X|8|@]|9|@]|A|$E|F]]|$1|O|3|P|5|6|7|Y|8|@]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

With Rails 5, all models are inherited from ApplicationRecord &amp; it gives nice way to include or extend other extension libraries. 

<pre><code># app/models/concerns/special_methods.rb
module SpecialMethods
 extend ActiveSupport::Concern

 scope :this_month, -&gt; { 
 where("date_trunc('month',created_at) = date_trunc('month',now())")
 }

 def foo
 # Code
 end
end
</code></pre>

Suppose the special methods module needs to be available across all models, include it in application_record.rb file. If we wants to apply this for a particular set of models, then include it in the respective model classes.

<pre><code># app/models/application_record.rb
class ApplicationRecord &lt; ActiveRecord::Base
 self.abstract_class = true
 include SpecialMethods
end

# app/models/user.rb
class User &lt; ApplicationRecord
 include SpecialMethods

 # Code
end
</code></pre>

If you want to have the methods defined in the module as class methods, extend the module to ApplicationRecord.

<pre><code># app/models/application_record.rb
class ApplicationRecord &lt; ActiveRecord::Base
 self.abstract_class = true
 extend SpecialMethods
end
</code></pre>

Hope it help others !

blocks|key|1320273|text|为了补充这个主题，我花了一些时间研究如何测试这些扩展(我沿着ActiveSupport::Concern路线进行了测试)。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1320274|下面是我如何建立一个模型来测试我的扩展。|1320275|describe+ModelExtensions+do
++describe+:some_method+do
++++it+'should+return+the+value+of+foo'+do
++++++ActiveRecord::Migration.create_table+:test_models+do+%7Ct%7C
++++++++t.string+:foo
++++++end

++++++test_model_class+=+Class.new(ActiveRecord::Base)+do
++++++++def+self.name
++++++++++'TestModel'
++++++++end

++++++++attr_accessible+:foo
++++++end

++++++model+=+test_model_class.new(:foo+=>+'bar')

++++++model.some_method.should+==+'bar'
++++end
++end
end|code-block|syntax|javascript|1320276|entityMap^0|U|M|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|R|8|@]|D|@]|E|$]]|$1|H|3|I|5|J|7|S|8|@]|D|@]|E|$K|L]]|$1|M|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|N|$]]

Just to add to this topic, I spent a while working out how to test such extensions (I went down the <code>ActiveSupport::Concern</code> route.)

Here's how I set up a model for testing my extensions.

<pre><code>describe ModelExtensions do
 describe :some_method do
 it 'should return the value of foo' do
 ActiveRecord::Migration.create_table :test_models do |t|
 t.string :foo
 end

 test_model_class = Class.new(ActiveRecord::Base) do
 def self.name
 'TestModel'
 end

 attr_accessible :foo
 end

 model = test_model_class.new(:foo =&gt; 'bar')

 model.some_method.should == 'bar'
 end
 end
end
</code></pre>

blocks|key|1320317|text|我有过|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1320318|ActiveRecord::Base.extend+Foo::Bar|code-block|syntax|javascript|1320319|在初始化器中|1320320|对于如下所示的模块|1320321|module+Foo
++module+Bar
++end
end|1320322|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|D|7|S|8|@]|9|@]|A|$E|F]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

I have 

<pre><code>ActiveRecord::Base.extend Foo::Bar
</code></pre>

in an initializer

For a module like below

<pre><code>module Foo
 module Bar
 end
end
</code></pre>

I've done some reading about how to extend ActiveRecord:Base class so my models would have some special methods. What is the easy way to extend it (step by step tutorial)?

Rails extending ActiveRecord::Base

我读过一些关于如何扩展ActiveRecord:基类的文章，这样我的模型就会有一些特殊的方法。扩展它的简单方法是什么(逐步教程)？

问Rails扩展ActiveRecord::Base
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