What is the role and application of generic data types in programming?

Generic data types allow creating functions, classes, or structures that work with different data types while maintaining type safety. This helps in writing more versatile and reusable code.

In iOS (Swift), generics enable, for example, creating an array or a function that can work with any type:

func swapValues<T>(_ a: inout T, _ b: inout T) {
    let temp = a
    a = b
    b = temp
}

var x = 5
var y = 10
swapValues(&x, &y)  // works with Int

var a = "hello"
var b = "world"
swapValues(&a, &b)  // works with String

Thus, generics increase code flexibility and reduce duplication.