Check out example codes for "extension swift". It will help you in understanding the concepts better.

Code Example 1

extension Example {
  // code here for the Example type...
}

Code Example 2

// A basic class
class MyClass {
    private let a = 5

    func getA() -> Int {
        return self.a
    } 
}

// An extension of that class - adds a function
extension MyClass {
    // Add an amount to the value of `a`
    func add(_ amount: Int) -> Int {
        return getA() + amount
    }
}

var mc = MyClass()

print(mc.getA()) // Direct part of class (Output: 5)
print(mc.add(5)) // Function from extension - called as if the fucntion were in the original definition (Output: 10)

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