ruby 如何在Ruby中的Array类中对数组的每个元素进行平方？
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How to square each element of an array in Array class in Ruby?
提问by mrdziuban
Part of my code is as follows:
我的部分代码如下：
class Array
def square!
self.map {|num| num ** 2}
self
end
end
When I call:
当我打电话时：
[1,2,3].square!
I expect to get [1,4,9], but instead I get [1,2,3]. Why is this the case? When I call:
我希望得到 [1,4,9]，但我得到的是 [1,2,3]。为什么会这样？当我打电话时：
[1,2,3].map {|num| num ** 2}
outside of the class method, I get the correct answer.
在课堂方法之外，我得到了正确的答案。
回答by Arup Rakshit
You have to use Array#map!, not Array#map.
您必须使用Array#map!，而不是Array#map。
Array#map-> Invokes the given block once for each element of self.Creates a new array containing the values returned by the block.
Array#map!-> Invokes the given block once for each element of self, replacing the element with the value returned by the block.
Array#map->为 self 的每个元素调用给定块一次。创建一个包含块返回值的新数组。
Array#map!->为 self 的每个元素调用给定块一次，用块返回的值替换该元素。
class Array
def square!
self.map! {|num| num ** 2}
end
end
[1,2,3].square! #=> [1, 4, 9]
