是否有“规则"?对于 Ruby 语法糖? [英] Are there "rules" for Ruby syntactic sugar?

问题描述

我正在学习 Ruby 的基础知识(刚刚开始)，并且遇到了 Hash.[] 方法.它被引入

I'm learning the basics of Ruby (just starting out), and I came across the Hash.[] method. It was introduced with

a = ["foo", 1, "bar", 2]
=> ["foo", 1, "bar", 2]
Hash[*a]
=> {"foo"=>1, "bar"=>2}

稍加思考，我发现 Hash[*a] 等价于 Hash.[](*a) 或 Hash.[]*a.我的问题是为什么会这样.是什么让您将 *a 放在方括号内，是否有某种规则可以在何时何地使用它"?

With a little thought, I figured out that Hash[*a] is equivalent to Hash.[](*a) or Hash.[] *a. My question is why that's the case. What is it that lets you put the *a inside the square brackets, and is there some kind of rule for where and when else "it" can be used?

我的措辞似乎引起了一些混乱.我不是在问阵列扩展.我明白了.我的问题基本上是:如果 [] 是一个方法名称，为什么可以将参数放在括号内?看起来几乎——但并不完全——就像说如果你有一个方法 Foo.dood，并且你想将字符串 "hey" 传递给它，那么你可以写Foo.do"hey"od.

My wording seems to be causing some confusion. I'm not asking about the array expansion. I get that. My question is basically: if [] is a method name, why is it okay to put arguments inside the brackets? It seems almost--but not quite--like saying that if you have a method Foo.dood, and you wanted to pass the string "hey" to it, then you could write Foo.do"hey"od.

推荐答案

ruby 有几个方法可以让你以一种特殊的方式调用.这些是您提到的 []、+、-、== 等其他人提及.另一个重要的例子是 something=(value) 形式的方法，它可以用 object.something = value 调用并允许你创建访问器.

There are a couple methods that ruby lets you call in a special way. These are the [] as you mentioned, the +, -, == and the like as someone else mentioned. Another important example are methods of the form something=(value) which can be called with object.something = value and allow you to create accessors.

有趣的事实 1:如果您定义一个 + 方法，您将免费获得 +=.

Fun fact 1: if you define a + method you get += for free.

有趣的事实 2:如果您定义了 <=>，您将获得所有比较方法，由 比较

Fun fact 2: if you define a <=> you get all comparison methods, courtesy of Comparable

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