这个 ruby​​ 注入魔法是如何工作的? [英] How does this ruby injection magic work?

问题描述

我今天看到了一个 ruby​​ 代码片段.

I saw a ruby code snippet today.

[1,2,3,4,5,6,7].inject(:+)  

<代码>=>28

[1,2,3,4,5,6,7].inject(:*)  

<代码>=>5040

这里的注入和我以前见过的完全不同，比如

The injection here is quite different from those I've seen before, like

[1,2,3,4,5,6,7].inject {|sum, x| sum + x}

请解释它是如何工作的?

Please explain how does it work?

推荐答案

没有魔法，符号(方法)只是可能的参数之一.这是来自文档:

There's no magic, symbol (method) is just one of the possible parameters. This is from the docs:

  # enum.inject(initial, sym) => obj
  # enum.inject(sym)          => obj
  # enum.inject(initial) {| memo, obj | block }  => obj
  # enum.inject          {| memo, obj | block }  => obj

我们的案例是第二个.

你也可以用传统块重写:

You can also rewrite it with traditional block:

op = :+   #  parameter of inject call
[1,2,3,4,5,6,7].inject {|sum, x| sum.send(op, x)} #  also returns 28

(回答它是如何工作的"部分)

(to answer "how does it work" part)

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