Ruby中的对象分配 [英] Object assignment in Ruby

问题描述

来自c ++背景，我对Ruby中的对象分配感到好奇.对于以下对象分配，应考虑哪些因素(如果有的话):

Coming from a c++ background I'm curious about object assignment in Ruby. What considerations (if any) should be made for the following object assignments:

class MyClass

  attr_accessor :a, :b

  def initialize(a, b)
    @a = a
    @b = b
  end

  def some_method
    puts "#{self.a} #{self.b}"
  end
end

m = MyClass.new("first", "last")
n = MyClass.new("pizza", "hello")

q = n
q.some_method

推荐答案

如果您熟悉C ++，则可能希望将Ruby中的每个变量(实例或其他实例)都视为对另一个对象的引用.由于Ruby中的所有内容都是对象，即使nil也是NilClass类型的对象，在任何情况下都适用.

If you're familiar with C++, then you might want to consider every variable in Ruby, instance or otherwise, as a reference to another object. Since everything in Ruby is an object, even nil, which is of type NilClass, this holds true under every circumstance.

要确定要引用的对象，可以使用object_id方法进行区分.这类似于在C ++中使用&转换为指针.

To determine which object you're referencing, you can use the object_id method to differentiate. That's similar to converting to a pointer using & in C++.

考虑一下:

a = "foo"
b = a

a.object_id == b.object_id
# => true

由于a是对该字符串的引用，而b是a的副本，因此它们实际上是对同一对象的不同引用.

Since a is a reference to that string, and b is a copy of a, then they are actually different references to the same object.

这很重要，因为修改对象的操作会同等影响所有对该对象的引用:

This is important because operations that modify an object affect all references to that equally:

a << "bar"
# => "foobar"
b
# => "foobar"

但是，创建 new 对象的操作不会修改所有副本:

However, operations that create a new object will not modify all copies:

a += "baz"
# => "foobarbaz"
b
# => "foobar"

!标识了Ruby中的许多方法，以区分就地版本和新副本版本，但这并非总是如此，因此您必须熟悉每种方法才能确定.

Many methods in Ruby are identified by a ! to distinguish in-place versus new-copy versions, but this is not always the case, so you have to be familiar with each method in order to be sure.

通常，一项任务会将旧的引用替换为新的引用，因此，根据经验，=将替换旧的引用.这适用于+=，-=，||=，&&=等.

Generally an assignment will replace an old reference with a new one, so as a rule of thumb, = will replace old references. This applies to +=, -=, ||=, &&= and so on.

根据Phrogz关于使用ObjectSpace._id2ref(object_id)将对象标识符转换为对象的注释进行了更新.

Updated based on Phrogz's comment about using ObjectSpace._id2ref(object_id) to convert an object identifier into an object.

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