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iOS Intermediate Swift Extensions and Protocols Extending a Native Type

Posted by Jon Senra Dearle
Jon Senra Dearle
4,316 Points

Code doesn't work against verifier but does on Xcode

The code provided doesn't seem to pass the test for the first code challenge of the chapter "Extensions & Protocols" from the Intermediate Swift course, however, it does compile and trying it on Xcode does seem to provide the expected results. Any idea why it isn't working?

types.swift 
// Enter your code below
extension String {
    func add (_ value: Int) -> Int? {
      if let ownValue = Int(self) {
        return ownValue + value
    } else {
        return nil
    }
  }
}

1 Answer

Clark Reilly
Clark Reilly
6,204 Points
Clark Reilly
Clark Reilly
6,204 Points

The compiler is really picky about how you name your arguments. You need to get rid of the “_” as the external name. The reason is that the checker is trying to call “1”.add(value: 2) and your code makes the correct syntax “1”.add(2) Which is confusing it.

Edit: fixed spelling error

Jon Senra Dearle
Jon Senra Dearle
4,316 Points

Thanks, Clark! That was indeed the issue and the change you proposed worked perfectly.