elixir - 确定 Map 是否具有某些键的正确方法

Question

我有一个必需 key 列表(required_keys):

["artist", "track", "year"]

和 map (参数):

%{"track" => "bogus", "artist" => "someone"}

我想确定是否 params有 required_keys .我来自 Ruby 背景，迭代对于 Elixir 似乎是错误的，但不确定如何进行模式匹配来做到这一点。

Answer 1

使用 Enum.all?/2 和 Map.has_key?/2 :

iex(1)> map = %{"track" => "bogus", "artist" => "someone"}
%{"artist" => "someone", "track" => "bogus"}
iex(2)> map2 = %{"track" => "bogus", "artist" => "someone", "year" => 2016}
%{"artist" => "someone", "track" => "bogus", "year" => 2016}
iex(3)> required_keys = ["artist", "track", "year"]
["artist", "track", "year"]
iex(4)> Enum.all?(required_keys, &Map.has_key?(map, &1))
false
iex(5)> Enum.all?(required_keys, &Map.has_key?(map2, &1))
true

but not sure how to pattern-match to do this

如果 required_keys，则无法进行模式匹配是动态的。如果是静态列表，则可以使用模式匹配:

iex(6)> match?(%{"artist" => _, "track" => _, "year" => _}, map)
false
iex(7)> match?(%{"artist" => _, "track" => _, "year" => _}, map2)
true