var dict1 = ["May 21": [1,2], "May 22": [3,4]] var dict2 = ["May 22": [5,6], "May 23": [7,8]] dict1.merge(dict2, uniquingKeysWith: +) print(dict1) // ["May 22": [3, 4, 5, 6], "May 23": [7, 8], "May 21": [1, 2]]var dict1 = ["May 21": [1,2], "May 22": [3,4]] var dict2 = ["May 22": [5,6], "May 23": [7,8]] dict1.merge(dict2, uniquingKeysWith: +) print(dict1) // ["May 22": [3, 4, 5, 6], "May 23": [7, 8], "May 21": [1, 2]]