❗specialize generic function

Applying constraints to individual functions

💾 程式

// generic function
func viewFactory<T: UIView>(numberOfView: Int) -> [T] {
    return Array(repeating: T(), count: numberOfView)
}

// ⛔️ Cannot explicitly specialize a generic function
let buttons = viewFactory<UIButton>(numberOfView: 3)

// ✅ infer from return type
let buttons: [UIButton] = viewFactory(numberOfView: 3)

// ✅ infer from method parameter type
func methodThatsNeedButtons(_ buttons: [UIButton]) {}
methodThatsNeedButtons(viewFactory(numberOfView: 3))

// ✅ explicitly put the type parameter (T) in parameter list
func viewFactory<T: UIView>(_ t: T.Type, numberOfView: Int) -> [T] {
    return Array(repeating: T(), count: numberOfView)
}

viewFactory(UIButton.self, numberOfView: 3)

📗 參考

• Sarunw ⟩ How to explicitly specialize a generic function in Swift ⭐️

• Sundell ⟩ Specialized extensions using generic type constraints ⟩ Applying constraints to individual functions

👥 相關

• Sundell ⟩ Specializing protocols in Swift

• shape.outlined()

🗣 討論

• Swift - Cannot specialize a non-generic definition

• GitHub ⟩ Swift ⟩ Specifying type arguments for uses of generic functions