Millised andmetüübid või objektid võivad toimida võtmetena sõnaraamatutes või hajutustabelites?

In dictionaries or hash tables, keys can be objects that meet the following requirements:

• Have correctly implemented equality comparison methods (equals in Java, isEqual in Swift) and hash code calculation (hashCode in Java).
• Are immutable or at least do not change after being used as a key, to avoid search problems.

In iOS (Swift), keys in dictionaries (Dictionary) are usually types that conform to the Hashable protocol. These can be:

• Standard types: String, Int, Double, Bool.
• User-defined structures or classes that implement the Hashable protocol.

Example:

struct Person: Hashable {
    let id: Int
    let name: String
}

var dict: [Person: String] = [:]
dict[Person(id: 1, name: "Alice")] = "Developer"

Therefore, keys must be hashable and immutable for the dictionary to work correctly.