iOS最完美的UITextField中输入金额，只能输入数字和小数点，保留两位小数点且0放在首位

@property (nonatomic, assign) BOOL isHaveDian;
@property (nonatomic, assign) BOOL isFirstZero;

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
    if (textField == self.amountTextField) {
   
        if ([textField.text rangeOfString:@"."].location==NSNotFound) {
            _isHaveDian = NO;
        }
        if ([textField.text rangeOfString:@"0"].location==NSNotFound) {
            _isFirstZero = NO;
        }
        
        if ([string length]>0)
        {
            unichar single=[string characterAtIndex:0];//当前输入的字符
            if ((single >='0' && single<='9') || single=='.')//数据格式正确
            {
                
                if([textField.text length]==0){
                    if(single == '.'){
                        //首字母不能为小数点
                        return NO;
                    }
                    if (single == '0') {
                        _isFirstZero = YES;
                        return YES;
                    }
                }
                
                if (single=='.'){
                    if(!_isHaveDian)//text中还没有小数点
                    {
                        _isHaveDian=YES;
                        return YES;
                    }else{
                        return NO;
                    }
                }else if(single=='0'){
                    if ((_isFirstZero&&_isHaveDian)||(!_isFirstZero&&_isHaveDian)) {
                        //首位有0有.（0.01）或首位没0有.（10200.00）可输入两位数的0
                        if([textField.text isEqualToString:@"0.0"]){
                            return NO;
                        }
                        NSRange ran=[textField.text rangeOfString:@"."];
                        int tt=(int)(range.location-ran.location);
                        if (tt <= 2){
                            return YES;
                        }else{
                            return NO;
                        }
                    }else if (_isFirstZero&&!_isHaveDian){
                        //首位有0没.不能再输入0
                        return NO;
                    }else{
                        return YES;
                    }
                }else{
                    if (_isHaveDian){
                        //存在小数点，保留两位小数
                        NSRange ran=[textField.text rangeOfString:@"."];
                        int tt= (int)(range.location-ran.location);
                        if (tt <= 2){
                            return YES;
                        }else{
                            return NO;
                        }
                    }else if(_isFirstZero&&!_isHaveDian){
                        //首位有0没点
                        return NO;
                    }else{
                        return YES;
                    }
                }
            }else{
                //输入的数据格式不正确
                return NO;
            }
        }else{
            return YES;
        }
    }
    return YES;
}

原文链接：http://blog.csdn.net/shiningchen322/article/details/51673848