“地图"有什么作用?方法在 Ruby 中做什么? [英] What does the "map" method do in Ruby?

问题描述

我是编程新手.有人能解释一下 .map 会做什么吗:

I'm new to programming. Can someone explain what .map would do in:

params = (0...param_count).map

推荐答案

map 方法接受一个可枚举对象和一个块，并为每个元素运行块，输出块的每个返回值(原始对象不变，除非你使用 map！):

The map method takes an enumerable object and a block, and runs the block for each element, outputting each returned value from the block (the original object is unchanged unless you use map!):

[1, 2, 3].map { |n| n * n } #=> [1, 4, 9]

Array 和 Range 是可枚举类型.带有块的 map 返回一个数组.map! 改变原始数组.

Array and Range are enumerable types. map with a block returns an Array. map! mutates the original array.

这有什么帮助，map! 和 each 之间有什么区别?下面是一个例子:

Where is this helpful, and what is the difference between map! and each? Here is an example:

names = ['danil', 'edmund']

# here we map one array to another, convert each element by some rule
names.map! {|name| name.capitalize } # now names contains ['Danil', 'Edmund']

names.each { |name| puts name + ' is a programmer' } # here we just do something with each element

输出:

Danil is a programmer
Edmund is a programmer

这篇关于“地图"有什么作用?方法在 Ruby 中做什么?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！