+ =的Ruby方法 [英] Ruby method for +=

问题描述

是否有办法使Ruby能够执行类似的操作?

Is there a way to make Ruby able to do something like this?

class Plane
  @moved = 0
  @x = 0
  def x+=(v) # this is error
    @x += v
    @moved += 1
  end
  def to_s
    "moved #{@moved} times, current x is #{@x}"
  end
end

plane = Plane.new
plane.x += 5
plane.x += 10
puts plane.to_s # moved 2 times, current x is 15

推荐答案

+=运算符与任何方法都不相关，它只是语法糖，当您编写a += b时，Ruby解释器将其转换为a = a + b ，对于转换为a.b = a.b + c的a.b += c也是一样.因此，您只需要根据需要定义方法x=和x:

The += operator is not associated to any method, it is just syntactic sugar, when you write a += b the Ruby interpreter transform it to a = a + b, the same is for a.b += c that is transformed to a.b = a.b + c. Thus you just have to define the methods x= and x as you need:

class Plane 
  def initialize
    @moved = 0
    @x = 0
  end

  attr_reader :x
  def x=(x)
    @x = x
    @moved += 1
  end

  def to_s
    "moved #{@moved} times, current x is #{@x}"
  end       

end

plane = Plane.new
plane.x += 5
plane.x += 10
puts plane.to_s
# => moved 2 times, current x is 15

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