Determine if string only contains numeric values

NSCharacterSet *decimalSet = [NSCharacterSet decimalDigitCharacterSet];
        
if (!([passcode rangeOfCharacterFromSet:decimalSet].location == NSNotFound)){
    //The string is full of numeric characters only. Yay!!!
}else{
    //some no good non-numeric characters have gotten in the party. Boo!!
}

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