UItextfiled限制输入数字

遵守textFieldDelegate，然后实现下面方法

-(BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{

NSCharacterSet * cs;

        cs = [[NSCharacterSet characterSetWithCharactersInString:NUMBERS]invertedSet];
        NSString * filtered = [[string componentsSeparatedByCharactersInSet:cs]componentsJoinedByString:@""];
        BOOL canChange = [string isEqualToString:filtered];
        
        return canChange;}