Iterating through references to variables in Swift - arrays

Question

I am looking for a way to change the values of multiple variables using iteration in Swift. An example would be something like this:
var a = false
var b = false
var c = false
func makeAllTrue() {
for n in [a, b, c] {
n = true
}
}
...but rather than an array of values, I want to iterate through an array of pointers/references to the variables above.
Any advice would be greatly appreciated.

Answer 1

var a = false
var b = false
var c = false
mutateValues(&a, &b, &c) { n in
n = true
}
print(a, b, c) // will be printed "true true true"
func mutateValues<Value>(_ values: UnsafeMutablePointer<Value>..., mutate: (inout Value) -> Void) {
values.forEach {
mutate(&$0.pointee)
}
}

Answer 2

It is possible to do this with key paths. Let's say the properties are in a class Foo:
class Foo {
var a = false
var b = false
var c = false
func makeAllTrue() {
for n in [\Foo.a, \Foo.b, \Foo.c] {
self[keyPath: n] = true
}
}
}
If Foo is a struct, use mutating func instead:
struct Foo {
var a = false
var b = false
var c = false
mutating func makeAllTrue() {
for n in [\Foo.a, \Foo.b, \Foo.c] {
self[keyPath: n] = true
}
}
}
However, if the class name is long, I don't think it is worth doing this way.
If these three properties are very related, I would not bother with the key path stuff and replace a, b and c with an array:
var abc = [false, false, false]
and have the for loop loop over the indices:
for i in abc.indices {
abc[i] = true
}

Answer 3

An Array in Swift is a struct, hence a value type.
Iterating over his children, and changing one, will not be possible unless:
The type of child is aa class (which is reference typed)
You iterate over the indices and change the real values!
E.G:
var a: Int = 1
var b: Int = 2
var array: [Int] = [a,b]
for index in array.indices {
array[index] += 1
}
print(array) // [2,3]