是否可以让 class.property = x 返回 x 以外的其他内容? [英] Is it possible to have class.property = x return something other than x?

问题描述

假设我有一个 Ruby 类:

Let's say I have a Ruby class:

class MyClass
  def self.property
    return "someVal"
  end

  def self.property=(newVal)
    # do something to set "property"
    success = true

    return success # success is a boolean
  end
end

如果我尝试做MyClass.property=x，整个语句的返回值总是x.许多基于 C 的/受启发的语言中的约定是返回布尔值成功"值 - 是否可以使用 Ruby 中的equals 语法"为 setter 执行此操作?

If I try and do MyClass.property=x, the return value of the whole statement is always x. It is a convention in a lot of C-based/inspired languages to return a boolean "success" value - is it possible to do this for a setter using the "equals syntax" in Ruby?

此外 - 如果这是不可能的，为什么不呢?允许equals setter"操作返回值有什么可以想象的缺点吗?

Furthermore - if this isn't possible, why not? Is there any conceivable downside to allowing an "equals setter" operation return a value?

推荐答案

一个缺点是你会打破链式赋值语义:

One downside is that you would break the chained assignment semantics:

$ irb 
irb(main):001:0> x = y = 3
=> 3
irb(main):002:0> p x
3
=> nil
irb(main):003:0> p y
3
=> nil
irb(main):004:0> 

考虑:

x = MyClass.property = 3

然后 x 将采用 true 如果这如您所料(右结合).对于使用您的界面并习惯于典型语义的人来说，这可能是一个惊喜.

Then x would take true if this worked as you had expected (right-associativity). That could be a surprise for people using your interface and used to the typical semantics.

你也让我想到了并行分配，例如:

You also got me thinking about parallel assignment, eg:

x, y = 1, 2

显然该表达式的返回值是具体实现...我想我不会链接并行分配:)

Apparently the return value from that expression is implementation specific... I guess I won't be chaining parallel assignments :)

好问题！

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