def func(var) 和 def func=(var) 有什么区别? [英] What is the difference between def func(var) and def func=(var)?

问题描述

在类定义中，这两种方法有什么区别?

In a class definition, what is the difference between these two methods?

def func(var)
...
end

def func=(var)
...
end

有没有，或者其中一个无效?

Is there any, or is one of them not valid?

推荐答案

解释一些关于 Ruby 中读写器也称为 getter/setter 方法的事情:

To explain some things about reader/writer AKA getter/setter methods in Ruby:

Ruby 不强制我们在 setter 的方法定义中使用 =.我们可以选择该方法是否有一个.

Ruby doesn't force us to use = in the method definition for a setter. We get to choose whether the method has one.

考虑一下:

class Foo

  # automagically creates:
  #   .v
  #   .v=
  attr_accessor :v

  def initialize(v)
    puts "inside initialize(#{ v })"
    @v = v
  end

  def setter(v)
    puts "inside setter(#{ v })" 
    @v = v 
  end

  def setter=(v) 
    puts "inside setter=(#{ v })"
    @v = v 
  end

end

f = Foo.new(1)
puts f.v

f.setter(2)
puts f.v

f.setter = 3
puts f.v

f.setter=(4)
puts f.v

f.v = 5
puts f.v

f.v=(6)
puts f.v

运行代码输出:

inside initialize(1)
1
inside setter(2)
2
inside setter=(3)
3
inside setter=(4)
4
5
6

= 只是方法名称中的另一个字母，因为 Ruby 足够聪明，知道它是否看到 f.setter = 3 它应该使用 setter=(v) 方法.

The = is simply another letter in the method name because Ruby is smart enough to know if it sees f.setter = 3 it should use the setter=(v) method.

Ruby 不强制使用 = 来设置变量，您可以在定义方法时决定它是否对您更有意义.我们使用 = 是惯用的，因为它有助于使 setter 看起来像一个赋值，消除了将所有 setter 命名为类似 set_v(v) 的冲动.

Ruby doesn't force using = to set a variable, you can decide if it makes more sense to you when you define the method. It is idiomatic that we use = because it helps make a setter look like an assignment, removing the urge to name all the setters something like set_v(v).

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