Is it possible to use a complex data structure as a key in a dictionary?

In dictionaries (Dictionary) in iOS (Swift), keys can only be of types that conform to the Hashable protocol. This means that a complex data structure can be a key if it implements hashing and equality comparison.

For example, if you have a structure:

struct Point: Hashable {
    let x: Int
    let y: Int
}

then you can use Point as a key in a dictionary:

var dict: [Point: String] = [:]
dict[Point(x: 1, y: 2)] = "Point A"

If the structure does not conform to Hashable, it cannot be used as a key. In this case, you need to either add conformance to the protocol or use a different key type.