Question

With Ruby 3 hash pattern matching, is it possible to specify that the rest contains only allowed keys? So far I only came up with this:

opts = { value: 5, limit: 10 } # valid
# opts = { value: 5 } # valid
# opts = { value: 5, foo: 10 } # not valid

case opts
in value:, **rest if rest.nil? || (rest.keys - %i[limit]).empty?
end

Something inspired by Flowtype might be in value:, limit?: or even in value: Integer, limit?: Integer

Answer 1

请注意,<代码>rest.nil?永远不会成为true<>/code>,因此你根本不需要:


case opts
in value:, **rest if (rest.keys - %i[limit]).empty?
end

www.un.org/spanish/ga/president

没有任何与你试图做的工作相匹配的模式,这与我能够利用其他模式一样接近:
opts = {value: 5, limit: 10}
case opts
in value:, **rest if rest in {limit:_}|{}
  [value, rest]
end

#=> [5, {:limit=>10}]

opts = {value: 5}
case opts
in value:, **rest if rest in {limit:_}|{}
  [value, rest]
end

#=> [5, {}]

opts = {value: 5, foo: 1}
case opts
in value:, **rest if rest in {limit:_}|{}
  [value, rest]
end

#=> (irb):346:in `<main> : {:value=>5, :foo=>1}: guard clause does not return true (NoMatchingPatternError)

Answer 2


也许我误解了这个问题,但你可以指出多种模式,例如:
options = [{ value: 5, limit: 10 }, 
        { value: 5 },
        { value: 5, foo: 10 }]

outputs = options.map do |opts| 
  {opts: opts,
   matched: case opts
    in {value: Integer, **nil} 
       matched value 
    in {value: Integer, limit: Integer, **nil}
       matched value and limit 
    else 
       no match 
  end}
end

#=> [{:opts=>{:value=>5, :limit=>10}, :matched=>"matched value and limit"}, 
#    {:opts=>{:value=>5}, :matched=>"matched value"}, 
#    {:opts=>{:value=>5, :foo=>10}, :matched=>"no match"}]

似乎符合这一要求。

参考<代码>**nil系指“和没有其他钥匙”。

友情链接