Ruby 需要的关键字参数

Question

For Ruby methods, the required keyword syntax is nice

def foo(bar:, baz:)
  :
end

foo(bar: true, baz: false) # OK
foo(bar: true) # missing keyword argument error

Can one 'splat' the list of required keywords with some kind of magic? ie,

required_keywords = [:bar, :baz]
def foo(magic(required_keywords))
  :
end

I expect not, but I'm often surprised with what Ruby can be persuaded to do.

Answer 1

The splat (*) and double spla t (**) operators allow a method to take an arbitrary number of arguments. The former will store the arguments in an array and the latter will store them in a hash.

There is also the options hash , which is an optional hash parameter, usually included as the last parameter at the method declaration. It can also take an arbitrary number of arguments (actually, they are plain hash items).

However, in both of the above cases, the number of arguments is unknown when you declare the method. Hence, you can't make an unknown number of arguments "required".

More info on splat, double splat and required keyword parameters is available at this blog post .