Does "didSet" work with tuples in arrays?

Question

I want to know if "didSet" works with tuples in arrays.

I'm writing something like the following code and I want to observe the tuple's value inside the array. Is it available to do that sort of thing?

var array :[(foo: Int, bar: Int)] = []]{
    didSet{
        // println code
    }
}

init(){
    var tuple = (foo: 0, bar:0)
    array = Array(count: 16, repeatedValue: tuple)
}

// change the value somewhere in the code
// and for example, want to println just only (and when) the value changed
array[3].foo = 100

Answer 1

Yes it works:

var array : [(foo: Int, bar: Int)] = [] {
    didSet {
        println("~~~~~~")
    }
}

let tup = (foo: 0, bar: 42)
array.append(tup)

println(array)
array[0].foo = 33
println(array)

didSet is executed each time the array is modified, as expected:

~~~~~~
[(0, 42)]
~~~~~~
[(33, 42)]

---

If you want to know the changed values, use "didSet" + "oldValue" and/or "willSet" + "newValue":

var array : [(foo: Int, bar: Int)] = [] {
    willSet {
        println(newValue)
    }
    didSet {
        println(oldValue)
    }
}

let tup = (foo: 0, bar: 42)
array.append(tup)
array[0].foo = 33

[(0, 42)]
[]
[(33, 42)]
[(0, 42)]

newValue and oldValue are both variables generated by Swift. Both "willSet" and "didSet" are called when the array is modified.

UPDATE:

You can access the actual object behind newValue and oldValue. Example:

var array : [(foo: Int, bar: Int)] = [] {
    willSet {
        println(newValue[0].foo)
    }
    didSet {
        if oldValue.count > 0 {
            println(oldValue[0].foo)
        } else {
            println(oldValue)
        }

    }
}

let tup = (foo: 0, bar: 42)
array.append(tup)
array[0].foo = 33