I need to compare entered textfield value with totalValue then need to show one error message in red colour

for that i have tried below code: here my total amount is 180... i need to show the red coloured text if i enter 181 in textfield but its showing only if i enter 4 characters for eg.. 1811 then its showing but i need immediately after i enter 181 in textfield... where am i wrong? please guide me.

func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
print(string)
if textField == self.amountTextField {
    if let char = string.cString(using: String.Encoding.utf8) {
        let isBackSpace = strcmp(char, "\\b")
        let enteredAmount = textField.text
        let totalAmnt = 180

        if enteredAmount?.toInteger() ?? 0 >= totalAmnt.toInteger(){
            amntErrorLbl.text = "Payment being made is more than quote"
        }
    }
}
return true
} 

o/p screenshots:

if i enter 181 in textfield then o/p

if i add 4 numbers then o/p

CodePudding user response：

var totalAmount = 180

func textFieldDidChangeSelection(_ textField: UITextField) {
    guard let text = textField.text,text.isNumbers else {
        return
    }
    guard let enteredAmount = Int(text) else {
        return
    }
    if enteredAmount > totalAmount {
        amntErrorLbl.text = "Entered more than total amount"
    }
    if enteredAmount < totalAmount {
        amntErrorLbl.text = "Entered less than total amount"
    }
    if enteredAmount == totalAmount {
        amntErrorLbl.text = "Entered equal amount"
    }
    
}


extension String {
    var isNumbers:Bool {
        guard self.count > 0 else { return false }
        let nums: Set<Character> = ["0", "1", "2", "3", "4", "5", "6", "7", "8", "9"]
        return Set(self).isSubset(of: nums)
    }
}