SOLVED: Day 7: Not understanding calling parameter vs value

@Caleb

Apr '20

This was a review question for "Using closures as parameters when they return values" section of Day 7 of 100 Days of Swift. The question was: This code is valid Swift - true or false?

func scoreToGrade(score: Int, gradeMapping: (Int) -> String) {
    print("Your score was \(score)%.")
    let result = gradeMapping(score)
    print("That's a \(result).")
}
scoreToGrade(score: 80) { (grade: Int) in
    if grade < 85 {
        return "Fail"
    }
}

I answered that it was valid Swift and I got it wrong. 🙁 The answer response was "The call to scoreToGrade() must return a value.", but I don't understand this. Isn't the (score: 80) in the scoreToGrade parameter going to be the return value? If not, where to the parameters go? What am I misunderstanding about parameters feeding in data to values feeding in data?
Lastly, how was this code supposed to look in order to work correctly?

Thanks for any help.

@roosterboy HWS+

Apr '20

Maybe this will help you figure it out...

What does the closure return if score >= 85?

@Caleb

Apr '20

Thank you, @roosterboy. I had been so focused on how the parameters and return values work that I didn't even notice that it needed to have an else statement.

Fixed!

func scoreToGrade(score: Int, gradeMapping: (Int) -> String) {
    print("Your score was \(score)%.")
    let result = gradeMapping(score)
    print("That's a \(result).")
}
scoreToGrade(score: 80) { (grade: Int) in
    if grade < 85 {
        return "Fail"
    } else {
        return "Success"
    }
}

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