我可以要求在Ruby中2.x的命名参数？

问题描述

限时删除！！

红宝石2.0是添加一个名为参数，就像这样：

Ruby 2.0 is adding named parameters, like this:

def say(greeting: 'hi')
  puts greeting
end

say                     # => puts 'hi'
say(greeting: 'howdy')  # => puts 'howdy'

我如何使用命名参数没有给一个默认值，因此它们需要？

How can I use named parameters without giving a default value, so that they are required?

推荐答案

有是用Ruby 2.0.0没有具体的办法，但你的，像语法高清美孚（A：，b :) ...

There is no specific way in Ruby 2.0.0, but you can do it Ruby 2.1.0, with syntax like def foo(a:, b:) ...

在红宝石2.0.x中，您可以通过将任何Ex pression抛出一个异常，例如强制执行：

In Ruby 2.0.x, you can enforce it by placing any expression raising an exception, e.g.:

def say(greeting: raise "greeting is required")
  # ...
end

如果你打算做这个有很多（且不能使用Ruby 2.1 +），你可以像使用一个辅助方法：

If you plan on doing this a lot (and can't use Ruby 2.1+), you could use a helper method like:

def required
  method = caller_locations(1,1)[0].label
  raise ArgumentError,
    "A required keyword argument was not specified when calling '#{method}'"
end

def say(greeting: required)
  # ...
end

say # => A required keyword argument was not specified when calling 'say'

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