Swift Generics

Swift Generics

Write reusable code with type parameters and constraints to ensure correctness without duplication.

Generic Functions

Generics let you write flexible, reusable functions and types.

Use a placeholder type name like T and constrain when needed.

Syntax:

• func name<T>(_ a: T) -> T
• struct Box<T> { ... }

Constraints:

• T: Comparable
• where clauses for more complex bounds.

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

var x = 1, y = 2
swapTwo(&x, &y)
print(x)
print(y)

This example defines a generic T-typed swap function and shows it working with integers.

Generic Constraints (where)

Constrain generic parameters to types that meet certain requirements, like Comparable, using where clauses.

func minValue<T: Comparable>(_ a: T, _ b: T) -> T { a < b ? a : b }

print(minValue(3, 7))        // 3
print(minValue("b", "a"))  // a

This example constrains T to Comparable so < can be used to pick a minimum.