Binary operator '*' cannot be applied to two 'Int?' operands

Question

Trying to calculate BMI ( body mass index ) as an app in Swift. Making the calculate function I cannot find the solution

@IBOutlet weak var height: UITextField!
@IBOutlet weak var weight: UITextField!

---

@IBAction func calculate(_ sender: UIButton) {

    }

@IBAction func reset(_ sender: UIButton) {
    }

func calculateIMC(){

    var textHeight = height.text
    var textWeight = weight.text
    var intHeight:Int? = Int(textHeight!) ?? 0
    var intWeight:Int? = Int(textWeight!) ?? 0

    let calculateHeight: Int? = (intHeight * intHeight)
}

Error message on the last line of code:

Binary operator '*' cannot be applied to two 'Int?' operands

Answer 1

The problem are the pointless and wrong type annotations. Remove them! All values are non-optional (and constants)

func calculateIMC(){

    let textHeight = height.text
    let textWeight = weight.text
    let intHeight = Int(textHeight!) ?? 0
    let intWeight = Int(textWeight!) ?? 0

    let calculateHeight = intHeight * intHeight // probably intHeight * intWeight
}

Answer 2

Don't unwrap a variable if you are not sure that its value is not nil. Use flatMap to get a required value in one line:

func calculateIMC() {
    let textHeight = height.text
    let textWeight = weight.text
    let intHeight = textHeight.flatMap { Int($0) } ?? 0
    let intWeight = textWeight.flatMap { Int($0) } ?? 0
    let calculateHeight = intHeight * intHeight
}

All code in this post was tested in Xcode 10.2.1.