iOS输入数字大小及小数点后面几位限制

[UITextField addTarget:self action:@selector(textFieldDidChange:) forControlEvents:UIControlEventEditingChanged];


//方法实现
- (void)textFieldDidChange:(UITextField *)textField
{

    //判断第一位是否为数字
    if ([textField.text isEqualToString: @"."]) {
        textField.text = @"";
    }
    
    //判断是否有两个小数点
    if (textField.text.length >= 2) {
        NSString *str = [textField.text substringToIndex:textField.text.length-1];
        NSString *strTwo = [textField.text substringFromIndex:textField.text.length-1];
        NSRange range = [str rangeOfString:@"."];
        if (range.location != NSNotFound && [strTwo isEqualToString:@"."]) {
            textField.text = [textField.text substringToIndex:textField.text.length-1];
        }
    }
    
    //小数点后面数字位数控制  （此时为小数点后一位，3改4就是两位    思路：取倒数第X个字符是否为小数点，是小数点的话，就不再允许输入）
    if (textField.text.length > 3) {
        NSString *myStr = [textField.text substringWithRange:NSMakeRange(textField.text.length-3 , 1)];
        if ([myStr isEqualToString:@"."]) {
            textField.text = [textField.text substringToIndex:textField.text.length-1];
        }
    }
    

    //最大值控制
    double doubleNum = [textField.text doubleValue];
    NSUInteger myNub = doubleNum;
    NSUInteger sum = 100.0;
    if (myNub > sum) {
        textField.text = [textField.text substringToIndex:textField.text.length-1];
    }
    
}

小白总结，欢迎打脸指正