iphone - 返回键的 Unichar 数字？

Question

我有一个快速问题，但我在任何地方都找不到。我将文本字段限制为仅包含数字、小数和负号。但这样做时，我关闭了返回键。有人知道iOS返回键的unichar数字吗？我以为是十三，但这是行不通的。

 - (BOOL)textField:(UITextField *)textField 
 shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
 {
     NSUInteger lengthOfString = string.length;
for (NSInteger loopIndex = 0;  loopIndex < lengthOfString; loopIndex++)
     {
         unichar character = [string characterAtIndex:loopIndex]; 
         if (character < 45) return NO; //45 - 57 we want
         if (character > 57) return NO; // -./0123456789
         if (character == 47) return NO; //47 we dont want, it is 
 //             if (character  == 36) return YES
     }
NSUInteger newLength = [textField.text length] + [string length] - range.length;
return (newLength > 5) ? NO : YES;
 }

Answer 1

您可能还有其他原因要检查输入。 (我认为与 '\n' 相比是有效的)，但这可能会更好:

-(BOOL)textFieldShouldReturn:(UITextField *)textField

编辑

处理浮点输入的更彻底的处理可能如下所示。关键思想是使用建议的替换构建候选字符串，然后测试整个字符串的语法有效性。通过这种方式，您可以处理用户在任意位置粘贴新文本而无需触摸代码。正则表达式只是一种紧凑/快速的指定语法的方法，您可以将自己的方法放入验证器中。

(我猜您可能希望将减号处理为不是字面上输入的一部分，而是需要负数的指示符。还假设长度限制是针对有效数字，而不仅仅是总字符数)

// answers true for a valid floating point literal, notwithstanding length
- (BOOL)isValidFloat:(NSString *)string {

    // optional sign, followed by zero or more digits, followed by decimal, followed by zero or more digits
    NSString *regex = @"([-+]?[0-9]*\\.?[0-9]*)";
    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"SELF MATCHES %@", regex];
    return [predicate evaluateWithObject:string];
}

#define kMAX_DIGITS  5

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

    NSString *currentText = textField.text;
    NSString *candidateText = [currentText stringByReplacingCharactersInRange:range withString:string];

    // accept a minus sign at any time. Place it in front if it's not already there
    if (string.length == 1 && [string characterAtIndex:0]=='-') {
        if ([currentText rangeOfString:string].location == NSNotFound) {
            textField.text = [string stringByAppendingString:currentText];
            // since we just inserted the minus, answer no so it won't be inserted twice
            return NO;
        }
    }

    // the decimal and minus sign don't count against the length constraint
    NSInteger decimalFudge = ([candidateText rangeOfString:@"."].location != NSNotFound)? 1 : 0;
    NSInteger minusFudge = (candidateText.length > 0 && [candidateText characterAtIndex:0]=='-')? 1 : 0;
    NSInteger maxLength = kMAX_DIGITS + decimalFudge + minusFudge;

    return (candidateText.length <= maxLength) && [self isValidFloat:candidateText];
}

- (BOOL)textFieldShouldReturn:(UITextField *)textField {
    [textField resignFirstResponder];
    return YES;
}