blocks|key|333074|text|我假设他们认为self.*更好，因为您可以肯定地说，它是一个类或实例方法，而不必向上滚动和搜索这个class+<<+self字符串。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|333075|entityMap^0|7|6|1D|D|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|M|8|@]|D|@]|E|$]]]|G|$]]

I assume that they think <code>self.*</code> is better because you can say for sure, it's a class or instance method, without having to scroll up and seaching this <code>class &lt;&lt; self</code> string.

blocks|key|333128|text|class+<<+self擅长将所有类方法保存在同一个块中。如果方法是以def+self.method形式添加的，那么就不能保证(除了约定和如意算盘之外)不会有额外的类方法隐藏在文件中。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|333129|def+self.method擅长显式地声明一个方法是一个类方法，而使用class+<<+self时，您必须自己找到容器。|333130|其中哪一个对你来说更重要是一个主观的决定，也取决于其他人有多少人在编写代码以及他们的偏好。|333131|entityMap^0|0|D|10|F|0|0|F|10|D|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@$9|M|A|N|B|C]|$9|O|A|P|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Q|8|@$9|R|A|S|B|C]|$9|T|A|U|B|C]]|D|@]|E|$]]|$1|H|3|I|5|6|7|V|8|@]|D|@]|E|$]]|$1|J|3|-4|5|6|7|W|8|@]|D|@]|E|$]]]|K|$]]

<code>class &lt;&lt; self</code> is good at keeping all of your class methods in the same block. If methods are being added in <code>def self.method</code> form then there's no guarantee (other than convention and wishful thinking) that there won't be an extra class method tucked away later in the file.
<code>def self.method</code> is good at explicitly stating that a method is a class method, whereas with <code>class &lt;&lt; self</code> you have to go and find the container yourself.
Which of these is more important to you is a subjective decision, and also depends on things like how many other people are working on the code and what their preferences are.

blocks|key|333221|text|如上所述，这两种风格似乎是等价的，但是使用class+<<+self可以将类方法标记为private或protected。例如：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|333222|class+UsingDefSelf
++def+self.a;+'public+class+method';+end
++private
++def+self.b;+'public+class+method!';+end
end

class+UsingSingletonClass
++class+<<+self
++++def+a;+'public+class+method';+end
++++private
++++def+b;+'private+class+method';+end
++end
end|code-block|syntax|javascript|333223|private仅影响实例方法。使用singleton类，我们定义了该类的实例方法，这些方法变成了包含类的类方法！|333224|我们还可以使用def+self将类方法标记为private|333225|class+UsingDefSelf
++def+self.a;+'private+class+method';+end
++def+self.b;+'private+class+method!';+end
++private_class_method+:a,+:b
++#+In+Ruby+2.1+there+is+an+alternative+syntax
++private_class_method+def+self.c;+'private+class+method!';+end
end|333226|但我们不能将它们标记为protected，因为没有protected_class_method。(但是，由于class是其singletonclass的唯一实例，所以私有类方法和受保护类方法几乎相同，只是它们的调用语法不同。)|333227|而且，与使用class+<<+self标记private类方法相比，它不那么容易，因为您必须列出private_class_method中的所有方法名称，或者在每个私有类方法定义中添加前缀private_class_method。|333228|entityMap^0|L|D|17|7|1F|9|0|0|0|7|0|7|8|M|7|0|0|B|9|P|M|0|6|D|L|7|1C|K|2M|K|0^^$0|@$1|2|3|4|5|6|7|W|8|@$9|X|A|Y|B|C]|$9|Z|A|10|B|C]|$9|11|A|12|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|13|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|14|8|@$9|15|A|16|B|C]]|D|@]|E|$]]|$1|M|3|N|5|6|7|17|8|@$9|18|A|19|B|C]|$9|1A|A|1B|B|C]]|D|@]|E|$]]|$1|O|3|P|5|H|7|1C|8|@]|D|@]|E|$I|J]]|$1|Q|3|R|5|6|7|1D|8|@$9|1E|A|1F|B|C]|$9|1G|A|1H|B|C]]|D|@]|E|$]]|$1|S|3|T|5|6|7|1I|8|@$9|1J|A|1K|B|C]|$9|1L|A|1M|B|C]|$9|1N|A|1O|B|C]|$9|1P|A|1Q|B|C]]|D|@]|E|$]]|$1|U|3|-4|5|6|7|1R|8|@]|D|@]|E|$]]]|V|$]]

As noted above, both styles seem to be equivalent, however using <code>class &lt;&lt; self</code> allows one to mark class methods as <code>private</code> or <code>protected</code>. For example:

<pre><code>class UsingDefSelf
 def self.a; 'public class method'; end
 private
 def self.b; 'public class method!'; end
end

class UsingSingletonClass
 class &lt;&lt; self
 def a; 'public class method'; end
 private
 def b; 'private class method'; end
 end
end
</code></pre>

<code>private</code> only affects instance methods. Using the singleton class, we are defining instance methods of that class, which turn into class methods of the containing class!

We can also mark class methods as <code>private</code> with <code>def self</code>:

<pre><code>class UsingDefSelf
 def self.a; 'private class method'; end
 def self.b; 'private class method!'; end
 private_class_method :a, :b
 # In Ruby 2.1 there is an alternative syntax
 private_class_method def self.c; 'private class method!'; end
end
</code></pre>

But we cannot mark them as <code>protected</code>, there is no <code>protected_class_method</code>. (However, since class is the only instance of its singletonclass, private class method and protected class methods are almost the same except their calling syntax is different.)

Also it is less easier than using <code>class &lt;&lt; self</code> to mark <code>private</code> class methods, since you have to list all method names in <code>private_class_method</code> or prefix <code>private_class_method</code> to every private class method definition.

blocks|key|549954|text|到目前为止，问题和答案只讨论了这两个选项：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|549955|class+MyClass
++def+self.method_name
++++..
++end
end

class+MyClass
++class+<<+self
++++def+method_name
++++++..
++++end
++end
end|code-block|syntax|javascript|549956|对于类方法，还有第三种选择需要考虑：|549957|class+MyClass
++def+MyClass.method_name
++++..
++end
end|549958|它并不流行，而且更冗长，但它是最明确的选项。|549959|如果你把Python和Ruby的self行为混为一谈，也不会那么令人困惑。|offset|length|style|CODE|549960|entityMap^0|0|0|0|0|0|G|4|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|W|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|X|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|Y|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|Z|8|@$O|10|P|11|Q|R]]|9|@]|A|$]]|$1|S|3|-4|5|6|7|12|8|@]|9|@]|A|$]]]|T|$]]

So far the question and answers only discuss these two options:

<pre><code>class MyClass
 def self.method_name
 ..
 end
end

class MyClass
 class &lt;&lt; self
 def method_name
 ..
 end
 end
end
</code></pre>

There's a third option to consider for class methods:

<pre><code>class MyClass
 def MyClass.method_name
 ..
 end
end
</code></pre>

It's not popular and is more verbose, but it's the most explicit option.

It's also less confusing if you mix up <code>self</code> behaviour between Python and Ruby.

This <a href="https://github.com/styleguide/ruby" rel="noreferrer">Ruby Style Guide</a> tells that is better using <code>self.method_name</code> instead of <code>class method_name</code>. But Why?

<pre><code>class TestClass
 # bad
 class &lt;&lt; self
 def first_method
 # body omitted
 end

 def second_method_etc
 # body omitted
 end
 end

 # good
 def self.first_method
 # body omitted
 end

 def self.second_method_etc
 # body omitted
 end
end
</code></pre>

Are there performance issues?

class << self vs self.method with Ruby: what's better?

容器

Python

这个告诉我们，使用self.method_name比使用class method_name更好。但是为什么呢？class TestClass # bad class << self def first_method # body omitted end def second_method...

问class vs self.method with <<：哪个更好？
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