How do you add a Dictionary of items into another Dictionary

Solution 1:

You can define += operator for Dictionary, e.g.,

func += <K, V> (left: inout [K:V], right: [K:V]) { 
    for (k, v) in right { 
        left[k] = v
    } 
}

Solution 2:

In Swift 4, one should use merging(_:uniquingKeysWith:):

Example:

let dictA = ["x" : 1, "y": 2, "z": 3]
let dictB = ["x" : 11, "y": 22, "w": 0]

let resultA = dictA.merging(dictB, uniquingKeysWith: { (first, _) in first })
let resultB = dictA.merging(dictB, uniquingKeysWith: { (_, last) in last })

print(resultA) // ["x": 1, "y": 2, "z": 3, "w": 0]
print(resultB) // ["x": 11, "y": 22, "z": 3, "w": 0]

Solution 3:

How about

dict2.forEach { (k,v) in dict1[k] = v }

That adds all of dict2's keys and values into dict1.