什么是“地图”方法做Ruby？ [英] What does the "map" method do in Ruby?

问题描述

我很习惯编程。有人可以解释什么 .map 将执行以下操作：

  params =（ 0 ... param_count）.map 
  

解决方案

map 方法使用可枚举的对象和块，并为每个元素运行块，从块中输出每个返回的值（原始对象不变，除非使用地图！）：

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

Array 和 Range 是枚举类型。带有块的 map 返回一个Array。 map！突变原始数组。

这在哪里有帮助，以及 map！和 each ？这里有一个例子：

  names = ['danil'，'edmund'] 
 
＃here我们将一个数组映射到另一个数组，通过一些规则
 names.map来转换每个元素！ {|名称| name.capitalize}＃现在名字包含['Danil'，'Edmund'] 
 
 names.each {| name |放置名称+'是一个程序员'}＃这里我们只是为每个元素做一些事情
  

输出：

  Danil是一个程序员
 Edmund是一个程序员
  

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

params = (0...param_count).map

解决方案

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

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

The output:

Danil is a programmer
Edmund is a programmer

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