Using Any instead of generics - swift

Question

Generics
Generic code enables you to write flexible, reusable functions and types that can work with any type, subject to requirements that you define. You can write code that avoids duplication and expresses its intent in a clear, abstracted manner.
Generics are one of the most powerful features of Swift, and much of the Swift standard library is built with generic code. In fact, you’ve been using generics throughout the Language Guide, even if you didn’t realize it. For example, Swift’s Array and Dictionary types are both generic collections. You can create an array that holds Int values, or an array that holds String values, or indeed an array for any other type that can be created in Swift. Similarly, you can create a dictionary to store values of any specified type, and there are no limitations on what that type can be.
The Problem That Generics Solve
Here’s a standard, nongeneric function called swapTwoInts(::), which swaps two Int values:
func swapTwoInts(_ a: inout Int, _ b: inout Int) {
let temporaryA = a
a = b
b = temporaryA
}
This function makes use of in-out parameters to swap the values of a
and b, as described in In-Out Parameters.
The swapTwoInts(::) function swaps the original value of b into a,
and the original value of a into b. You can call this function to swap
the values in two Int variables:
var someInt = 3
var anotherInt = 107
swapTwoInts(&someInt, &anotherInt)
print("someInt is now \(someInt), and anotherInt is now \(anotherInt)")
// Prints "someInt is now 107, and anotherInt is now 3" The
swapTwoInts(::) function is useful, but it can only be used with Int
values. If you want to swap two String values, or two Double values,
you have to write more functions, such as the swapTwoStrings(::) and
swapTwoDoubles(::) functions shown below:
func swapTwoStrings(_ a: inout String, _ b: inout String) {
let temporaryA = a
a = b
b = temporaryA
}
func swapTwoDoubles(_ a: inout Double, _ b: inout Double) {
let temporaryA = a
a = b
b = temporaryA
}
My question:
Instead of using generics function we could have just used Any type as the argument type right, that will simple as this
func swapTwoInts(_a:inout Any,_b:inout Int){
let temporaryA = a
a = b
b = temporaryA
}
So how to plays important role in swift?
Can I write code without generics like this
var num = 3
var numtwo = 5
print(num)
print(numtwo)
func swap(_ a: inout Any, _ b: inout Any){
let tempA=a
a=b
b=tempA
}
swap(a: &num, b: &numtwo)

Answer 1

In swift, you can assign value to a variable ONLY if the type of the variable is same with the value. So imagine you have this:
var a = 1
var b = 2
func swapTwoValues(_ a: inout Any, _ b: inout Any) {
let temporaryA = a
a = b
b = temporaryA
}
swapTwoValues(&a, &b) // <- Cannot pass immutable value as inout argument: implicit conversion from 'Int' to 'Any' requires a temporary
So compiler forces you to implicitly assign Any for the type of the variables. This is not what you want I think. So you have to tell the compiler that it doesn't matter the type of the arguments. The only thing matters is they both have same type to fulfill compilers need. So to achieve this, you can use generic or some kind of protocol.
func swapTwoValues<T>(_ a: inout T, _ b: inout T) {
let temporaryA = a
a = b
b = temporaryA
}
swapTwoValues(&a, &b) // Done
Tip: You can swap values with tuple in single line of code without using temporaryVar like this: (Even without function and generic and etc.)
(a, b) = (b, a)