create a generic function in swift

In Swift, we can create generic functions which can work with a variety of data types. This is achieved through the use of type parameters.

To create a generic function, we start by defining the function signature with the name, parameters, and return type. We then add angle brackets "<>" after the function name and list the type parameters inside the brackets. Type parameters are placeholders for actual data types that will be used when the function is called.

Here's an example of a generic function that swaps two variables of any data type, using a generic type parameter T with a type constraint that specifies that T must conform to the Equatable protocol:

main.swift
func swapTwoValues<T: Equatable>(_ a: inout T, _ b: inout T) {
    if a == b {
        return
    }
    let temp = a
    a = b
    b = temp
}
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In the example above, the type parameter T must conform to the Equatable protocol, which provides the equal to operator to compare its values.

We can call this function with any data type that conforms to the Equatable protocol, like this:

main.swift
var num1 = 5
var num2 = 10
swapTwoValues(&num1, &num2)
print("num1 = \(num1), num2 = \(num2)") // Output: num1 = 10, num2 = 5

var str1 = "hello"
var str2 = "world"
swapTwoValues(&str1, &str2)
print("str1 = \(str1), str2 = \(str2)") // Output: str1 = world, str2 = hello
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In the example above, we first call the function with two integer variables, and then with two string variables. The function works correctly for both cases, because it is generic and can work with any data type that conforms to the Equatable protocol.