find the union of two maps in swift

In Swift, you can use the merge function to combine two dictionaries. Here's an example:

main.swift
var map1 = ["A": 1, "B": 2]
var map2 = ["B": 3, "C": 4]

map2.merge(map1) { (_, new) in new }

print(map2) // prints ["A": 1, "B": 2, "C": 4]
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In this example, we first create two dictionaries map1 and map2. We want to take the union of these dictionaries, where if there are common keys, we take the value from map2.

We call the merge function on map2, which will merge the key-value pairs from map1. The closure we pass to merge is used to specify what to do when there are common keys. In our case, we simply take the value from map1.

After calling merge, map2 will contain the union of the key-value pairs from map1 and map2.