方法的 ruby​​ 关键字参数 [英] ruby keyword arguments of method

问题描述

如何像 rails 一样声明一个带有关键字参数的方法.一些例子可能是

How can I declare a method with keyword arguments just like rails do. some examples may be

Person.find(:all, :conditions => "..."). 

如何使用符号创建与上述类似的方法?

How can I use symbols to create methods similar to the above?

我对 ruby​​ 很陌生.提前致谢！

I am very new to ruby. Thanks in advance!

推荐答案

Ruby 实际上没有关键字参数.Rails 正在利用 Ruby 的一个特性，它允许您省略散列周围的大括号.例如，对于find，我们真正调用的是:

Ruby doesn't actually have keyword arguments. Rails is exploiting a feature of Ruby which lets you omit the braces around a hash. For example, with find, what we're really calling is:

Person.find(:all, { :conditions => "...", :offset => 10, :limit => 10 } )

但是如果散列是方法的最后一个参数，您可以省略大括号，它仍然会被视为散列:

But if the hash is the last argument of the method, you can leave out the braces and it will still be treated as a hash:

Person.find(:all, :conditions => "...", :offset => 10, :limit => 10)

您可以在自己的方法中使用它:

You can use this in your own methods:

def explode(options={})
    defaults = { :message => "Kabloooie!", :timer => 10, :count => 1 }
    options = defaults.merge(options)

    options[:count].times do
        sleep options[:timer]
        puts options[:message]
    end
end

然后调用它:

explode :message => "Meh.", :count => 3

或者不带参数调用它，导致使用所有默认值:

Or call it without an argument, resulting in all default values being used:

explode

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