(一元)*运算符在此Ruby代码中做什么? [英] What does the (unary) * operator do in this Ruby code?

问题描述

给出Ruby代码

line = "first_name=mickey;last_name=mouse;country=usa" 
record = Hash[*line.split(/=|;/)] 

除了*运算符外，我理解第二行中的所有内容-它在做什么，相关文档在哪里? (您可能会猜到，搜索这种情况非常困难...)

解决方案

*是 splat 运算符.

它将Array扩展为参数列表，在本例中为Hash.[]方法的参数列表. (更确切地说，它扩展了对to_ary/to_a或Ruby 1.9中的to_a作出响应的任何对象.)

为了说明，以下两个语句是相等的:

method arg1, arg2, arg3
method *[arg1, arg2, arg3]

它也可以在不同的上下文中使用，以捕获方法定义中所有剩余的方法参数.在这种情况下，它不会扩展，而是结合在一起:

def method2(*args)  # args will hold Array of all arguments
end

此处有更多详细信息.

Given the Ruby code

line = "first_name=mickey;last_name=mouse;country=usa" 
record = Hash[*line.split(/=|;/)] 

I understand everything in the second line apart from the * operator - what is it doing and where is the documentation for this? (as you might guess, searching for this case is proving hard...)

解决方案

The * is the splat operator.

It expands an Array into a list of arguments, in this case a list of arguments to the Hash.[] method. (To be more precise, it expands any object that responds to to_ary/to_a, or to_a in Ruby 1.9.)

To illustrate, the following two statements are equal:

method arg1, arg2, arg3
method *[arg1, arg2, arg3]

It can also be used in a different context, to catch all remaining method arguments in a method definition. In that case, it does not expand, but combine:

def method2(*args)  # args will hold Array of all arguments
end

Some more detailed information here.

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