Ruby条件分配和私有方法

从下面的代码中可以看出,|| =运算符正在从类外部进行求值.

class Foo
  attr_reader :bar

  def baz
    self.bar ||= 'baz'
  end

  private

  attr_writer :bar
end

puts Foo.new.baz
# => in `baz': private method `bar=' called for #<Foo:0x007fd9720829a8> (NoMethodError)

从Ruby: Official expansion of ||= conditional assignment operator接受的答复中引用：

In other words,the expansion c = c || 3 is (excluding bugs like in pre-1.9) correct.

将baz方法重写为self.bar = self.bar || ‘baz’不会引起错误.

我正在寻找一个关于Ruby如何以及为什么以这种方式行事的明确答案,因为它似乎是反直觉的.

这个行为存在于Ruby版本1.9.3,2.0.0和2.1.2上,这导致我相信这不是一个错误.

解决方法

看起来像一个 bug.

更新：bug在中继线是fixed,是slated for back porting to 2.1 and 2.0.

请注意,问题比这更普遍,对于所有缩写的分配,它不再是有条件的缩写分配：

private def foo=(*) end
public  def foo; 0  end

self.foo =  42

self.foo += 42
# private method `foo=' called for main:Object (NoMethodError)

private :foo

self.foo += 42
# private method `foo' called for main:Object (NoMethodError)