[英]How to write a method in ruby that takes hash-style, square bracketed arguments, like mymethod[arg]?
I want to write a method in ruby to replace a current method that simply returns a hash.我想用 ruby 编写一个方法来替换当前只返回散列的方法。
So currently we have this所以目前我们有这个
def some_stats
{
:foo => "bar",
:zoo => "zar"
}
end
which can be called like this:可以这样调用:
some_stats[:foo]
I want to replace this with a method that is called with :foo, which does some more complicated things that just building a hash.我想用一个用 :foo 调用的方法来替换它,它会做一些更复杂的事情,只是构建一个散列。 However, I'd like it to be called in the same way, with the square bracket notation.
但是,我希望以相同的方式调用它,并使用方括号表示法。 EG
例如
#this is a bit pseudo-cody but hopefully you get the idea.
def some_stats[](key)
if key.to_s =~ /something/
#do something
return something
else
#do something else
return something_else
end
end
This would still be called like some_stats[:foo]
这仍然会像
some_stats[:foo]
一样被调用
I can't work out the syntax for defining the method name: the above, def some_stats[](key)
doesn't work.我无法计算出定义方法名称的语法:上面的
def some_stats[](key)
不起作用。 I feel like this should be possible though.不过我觉得这应该是可能的。
You're quite close.你很接近。
object[sth]
is just a syntax sugar for object.[](sth)
. object[sth]
只是object.[](sth)
的语法糖。 So to do what you need you have to define some_stats
method that returns the object which defines []
method:因此,要执行您需要的操作,您必须定义
some_stats
方法,该方法返回定义[]
方法的对象:
class Stats
def [](key)
if key.to_s =~ /something/
#do something
return something
else
#do something else
return something_else
end
end
def some_stats
Stats.new
end
some_stats[:something_new] #=> something
some_stats[:not_new] #=> something_else
Your original method is not called with square brackets ;您的原始方法不是用方括号调用的; it is called without any argument , but returns an object (in your case a
Hash
), which has method :[]
defined and hence understands square brackets.它在没有任何参数的情况下被调用,但返回一个对象(在你的情况下是一个
Hash
),它定义了方法:[]
,因此理解方括号。 Your method call is equivalent to您的方法调用相当于
(some_stats())[:foo]
or, more explicitly, to或者,更明确地说,
x = some_stats()
x[:foo]
Therefore you need - inside your method return an instance of some class which offers the []
method.因此你需要 - 在你的方法中返回一个提供
[]
方法的类的实例。 Say you have written a class named MyClass
which has a []
defined.假设您编写了一个名为
MyClass
的类,它定义了一个[]
。 You could then write a function然后你可以写一个函数
def some_stats
if _your condition goes here_
{ ... } # Return your Hash
else
Myclass.new
end
end
This would be used as这将用作
some_stats[:whatever]
However, to be really useful, your condition would make use of a parameter to the method, ie但是,要真正有用,您的条件将使用该方法的参数,即
def some_stats(param)
if param < 4000
{ ... } # Return your Hash
else
Myclass.new
end
end
And you would invoke it by你会调用它
some_stats(4711)[:whatever]
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