Generics & Casting

Generics

Use <T> to write functions and types that work with any type:

func first<T>(items: Array<T>) -> Optional<T> {
    if items.isEmpty() { return null }
    return items[0]
}

let names: Array<string> = ["Alice", "Bob"]
let name = first(names)   // Optional<string>

Built-in generic types

Array<string>
Dictionary<string, int>
Optional<Player>
Result<float>
Array<Dictionary<string, Player>>   // nesting works

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Type casting

Use as to convert between numeric types:

let n = 3.9 as int      // 3 (truncates)
let f = 42 as float     // 42.0