Existence of Key-Value Item
This lesson focuses on two major concepts: how to find a value associated with a key and how to delete a key-value pair from a map.
We'll cover the following...
Testing the existence of a key
We saw in the previous lesson that val1 = map1[key1] returns the value val1 associated with key1. If key1 does not exist in the map, val1 becomes the zero-value for the value’s type, but this is ambiguous. Now we can’t distinguish between this case or the case where key1 does exist and its value is the zero-value! In order to test this, we can use the following comma ok form:
val1, isPresent = map1[key1]
The variable isPresent will contain a Boolean value. If ...