+= ruby​​ 中的运算符重载 [英] += operator overloading in ruby

问题描述

class Fracpri
attr_accessor:whole, :numer, :denom, :dec, :flofrac
def initialize()
    puts "Hey! It's an empty constructor"
end
def getFraction(whole,numer,denom)
    @whole=whole
    @numer=numer
    @denom=denom
end
def showFraction
    puts "#{whole} #{numer}/#{denom}"
end
def +=(obj)
    if(self.whole+(self.numer.to_f/self.denom.to_f) < obj.whole+(obj.numer.to_f/obj.denom.to_f))
        puts "Yes"
    else
        puts "No"
    end
end

end
puts "10 question"
r3=Fracpri.new()
r3.getFraction(1,2,3)
r2=Fracpri.new()
r2.getFraction(4,6,5)
r1=Fracpri.new()
r1.getFraction(2,6,5)
r1 += r2

这是我收到的错误消息:

this is the error message I'm getting:

syntax error, unexpected '=', expecting ';' or '\n'

    def +=(obj)
          ^

 syntax error, unexpected keyword_end, expecting end-of-input

建议我如何纠正这个错误，以便我可以执行重载，我需要使用+="运算符添加一个常量

suggest me how to rectify this error so that i can perform overloading,i need to add a constant using "+=" operator

推荐答案

不能覆盖 =，也不能覆盖诸如 += 之类的变体.这些是内置的关键字，而不是 方法，例如 +.

It is not possible to override =, nor variants such as +=. These are built in keywords and not methods such as +.

如果您将补丁从 def +=(obj) 更改为 def +(obj)，您仍然可以调用 r1 += r2> 并且它的效果与您修补 += 的效果相同.这是因为 += 在幕后调用您修补的 + 方法.

If you change your patch from def +=(obj) to def +(obj), you can still call r1 += r2 and it will have the same effect as if you'd patched +=. This is because += is calling your patched + method under the hood.

顺便说一下，你的 + 方法实际上并没有返回一个值，所以任何时候你调用 += 它总是会导致 nil .... 但它看起来这仍然是一个 WIP，所以希望你能解决这个问题.

By the way, your + method doesn't actually return a value so any time you call += it will always result in nil .... but it seems like this is still a WIP so hopefully you can sort that bit out.

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