Swift抽象返​​回类型的方法

Question

I wanna to create a function that returns a value an array from the UserDefauts, like this:

func GetBool(name: String) -> Bool {
    let defaults = UserDefaults.standard
    return defaults.bool(forKey: name)
}

func GetBoolArray(name: String) -> [Bool] {
    let defaults = UserDefaults.standard
    return defaults.array(forKey: name) as? [Bool] ?? [Bool]()
}

But I don't wanna create a function for Bool, another for Int, another for CGFloat, etc.

What's the best way to abstract all functions (for Bool, Int, etc.) into one (one for single values, other for array values)?

Answer 1

Would something like this work for you?

func GetValue(name: String) -> Any? {
    let defaults = UserDefaults.standard
    return defaults.value(forKey: name)
}

func GetValueArray(name: String) -> [Any] {
    let defaults = UserDefaults.standard
    return defaults.array(forKey: name) ?? [Any]()
}

Note that the first function needs to be unwrapped when used because the key you used might not match a value. Also, I believe array for key works with NSArrays only so the first function would probably work for both cases for you.

Answer 2

Thanks to @Martin R, I discovered swift generics, this is what I was looking for

func GetValue<T>(name: String) -> T {
    let defaults = UserDefaults.standard
    return defaults.value(forKey: name) as! T
}

func GetArray<T>(name: String) -> [T] {
    let defaults = UserDefaults.standard
    return defaults.array(forKey: name) as? [T] ?? [T]()
}