Ruby:用 block 初始化对象实例

Question

是否可以在不创建临时变量的情况下初始化 Object 实例、对其执行操作并返回该实例？

例如:

def create_custom_object
  Object.new do |instance|
    instance.define_singleton_method(:foo) { 'foo' }
  end
end 
# returns an instance, but defines nothing :(
def create_custom_object
  Object.new do 
    self.define_singleton_method(:foo) { 'foo' }
  end
end
# same thing 

而不是:

def create_custom_object 
  object = Object.new
  object.define_singleton_method(:foo) { 'foo' }
  object
end 

Answer 1

你可以使用 tap :

Yields self to the block, and then returns self.

例子:

def create_custom_object
  Object.new.tap { |o| o.define_singleton_method(:foo) { 'foo' } }
end

object = create_custom_object
#=> #<Object:0x007f9beb857b48>

object.foo
#=> "foo"