确定地图是否具有某些键的正确方法
问题描述：
我有一个必填键（required_keys）列表：
I have a List of required keys (required_keys):
["artist", "track", "year"]
和地图（参数）：
%{"track" => "bogus", "artist" => "someone"}
，我想确定参数具有 required_keys 。我来自Ruby背景，对于Elixir来说，迭代似乎是错误的，但是不确定如何进行模式匹配。
and I want to determine if the params has the required_keys. I'm coming from a Ruby background and iterating seems wrong for Elixir, but not sure how to pattern-match to do this.
答
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
但不确定如何进行模式匹配来做到这一点
but not sure how to pattern-match to do this
模式匹配不正确如果 required_keys 是动态的，则可能。如果是静态列表，则可以使用模式匹配：
Pattern matching is not possible if required_keys is dynamic. If it's a static list, you could use pattern matching:
iex(6)> match?(%{"artist" => _, "track" => _, "year" => _}, map)
false
iex(7)> match?(%{"artist" => _, "track" => _, "year" => _}, map2)
true