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iOS Intermediate Swift Extensions and Protocols Extending a Native Type

Richard Pitts
PLUS
Richard Pitts
Courses Plus Student 1,243 Points

What is the correct answer?

I have no clue, but am looking for the correct answer and maybe a little explanation relative to my attempt. Thanks.

types.swift
// Enter your code below

extension String { add(value: Int) } -> Bool return Int?

1 Answer

David Papandrew
David Papandrew
8,386 Points

Hi Richard,

You need to create a new method called "add". The method may or may not return an Int. So you are headed in the right direction with your solution above.

In the body of the method, you want to check if a string ("self") calling the add method can be recast as an Integer or not. So you'll use an if statement to do this.

Here's the code:

extension String {
    func add(value: Int) -> Int? {
        if Int(self) != nil {
            return Int(self)! + value
        } else {
            return nil
        }
    }
}

And to use the extension:

"2".add(value: 10)  // <== returns 12
"Dog".add(value: 10)   // <== returns nil