ios - Better way to check for a Int in a textbox -

i learning xcode , creating program textbox(txt box) in user enters value, button (btncalc) performs calculation, , label (lblcalcdnumber) shows calc'd number. have selected number pad displayed dropdown keyboard want check make sure if enter other number nothing happens. code have works feel there should cleaner solution. essential want them enter integers in textbook.

    // mark: actions @ibaction func btncalc(sender: uibutton) {          // let txtbox text beome int     let number1 = int(txtbox.text!)         // let possibleint convert mystring int check nil, txtbox becomes optional     let possibleint = int(txtbox.text!)     let number = 25      if possibleint != nil {         let combinednumber = "\(int(number1!) * number)"         lblcalcednumber.text = combinednumber     }     else {         txtbox.text = ""         txtbox.placeholder = "please enter valid number"      }  } 

you can use if , let create optional. if value not nil cast possibleint, otherwise, evaluate false.

@ibaction func btncalc(sender: uibutton) {      if let possibleint = int(txtbox.text!) {         let combinednumber = "\(possibleint * 25)"         lblcalcednumber.text = combinednumber     }     else {         txtbox.text = ""         txtbox.placeholder = "please enter valid number"     } }