如何将参数传递给 array.map 快捷方式? [英] How do I pass an argument to array.map short cut?

问题描述

给定以下数组a:

a = [1, 2, 3, 4, 5]  

我该怎么做:

a.map { |num| num + 1 }  

使用简写:

a.map(&:+ 1)  

或:

a.map(&:+ 2)  

其中 1 和 2 是参数?

where 1 and 2 are the arguments?

推荐答案

你不能这样做.& 运算符用于将符号转换为过程.

You can't do it like this. The & operator is for turning symbols into procs.

a = [1, 2, 3, 4, 5]  
puts a.map(&:to_s) # prints array of strings
puts a.map(&:to_s2) # error, no such method `to_s2`.

& 是 to_proc:

def to_proc
  proc { |obj, *args| obj.send(self, *args) }
end

它创建并返回新的过程.如您所见，您无法向此方法传递任何参数.您只能调用生成的过程.

It creates and returns new proc. As you see, you can't pass any parameters to this method. You can only call the generated proc.

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