map(&:name)在Ruby中是什么意思? [英] What does map(&:name) mean in Ruby?

问题描述

我在 a RailsCast 中找到了这段代码:

I found this code in a RailsCast:

def tag_names
  @tag_names || tags.map(&:name).join(' ')
end

map(&:name)中的(&:name)是什么意思?

推荐答案

这是tags.map(&:name.to_proc).join(' ')

如果foo是具有to_proc方法的对象，则可以将其作为&foo传递给方法，该方法将调用foo.to_proc并将其用作方法的块.

If foo is an object with a to_proc method, then you can pass it to a method as &foo, which will call foo.to_proc and use that as the method's block.

Symbol#to_proc方法最初由ActiveSupport添加，但已集成到Ruby 1.8.7中.这是它的实现:

The Symbol#to_proc method was originally added by ActiveSupport but has been integrated into Ruby 1.8.7. This is its implementation:

class Symbol
  def to_proc
    Proc.new do |obj, *args|
      obj.send self, *args
    end
  end
end

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