KeyValuePattern

KeyValuePattern[{patt1, ...}] is a pattern object that represents an association or list of rules that includes elements matching each of the patti.

Examples

Match an association with specific keys:

MatchQ[<|"a" -> 1, "b" -> 2|>, KeyValuePattern[{"a" -> _}]]
(* True *)

Use in pattern matching:

Cases[{<|"x" -> 1|>, <|"y" -> 2|>, <|"x" -> 3|>}, KeyValuePattern[{"x" -> _}]]
(* {<|"x" -> 1|>, <|"x" -> 3|>} *)

Please visit the official Wolfram Language Reference for more details.