限制 UITextField 的字符数量和类型

Question

我有两个文本字段，希望限制字符的数量和类型。我分别使用以下代码来实现每个功能，但是找不到一种同时实现两个功能的方法。

要限制字符类型：

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
    // Only characters in the NSCharacterSet you choose will insertable.
    NSCharacterSet *invalidCharSet = [[NSCharacterSet characterSetWithCharactersInString:@"abcdefgABCDEFG"] invertedSet];
    NSString *filtered = [[string componentsSeparatedByCharactersInSet:invalidCharSet] componentsJoinedByString:@""];
    return [string isEqualToString:filtered];
}

并且限制字符数量：

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
 if (textField.text.length >= 10 && range.length == 0)
 return NO;
return YES;
}

- Tool

Answer 1

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
    if (textField.text.length >= 10 && range.length == 0)
       return NO;
    // Only characters in the NSCharacterSet you choose will insertable.
    NSCharacterSet *invalidCharSet = [[NSCharacterSet characterSetWithCharactersInString:@"abcdefgABCDEFG"] invertedSet];
    NSString *filtered = [[string componentsSeparatedByCharactersInSet:invalidCharSet] componentsJoinedByString:@""];
    return [string isEqualToString:filtered];
}

---

经过编辑

如果您想为第三个文本字段添加不同的条件，则可以按照以下方式操作。
创建第三个文本字段的引用，例如 thirdField

然后使用以下代码：

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
    if (textField == thirdField) {
        //your contion e.g
        if (textField.text.length < 7) {
            return YES;
        } else {
            return NO;
        }        
    }
    else {
        if (textField.text.length >= 10 && range.length == 0)
            return NO;
        // Only characters in the NSCharacterSet you choose will insertable.
        NSCharacterSet *invalidCharSet = [[NSCharacterSet characterSetWithCharactersInString:@"abcdefgABCDEFG"] invertedSet];
        NSString *filtered = [[string componentsSeparatedByCharactersInSet:invalidCharSet] componentsJoinedByString:@""];
        return [string isEqualToString:filtered];
    }
}

- Inder Kumar Rathore

---

如果我添加了第三个文本字段，但想要对其应用不同的条件，我该怎么做？ - Tool

Answer 2

这是一种非常干净的方法，可以限制在UITextField中输入的字符。此方法允许使用多个预定义的NSCharacterSet。

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

    NSMutableCharacterSet *allowedCharacters = [NSMutableCharacterSet alphanumericCharacterSet];
    [allowedCharacters formUnionWithCharacterSet:[NSCharacterSet whitespaceCharacterSet]];
    [allowedCharacters formUnionWithCharacterSet:[NSCharacterSet symbolCharacterSet]];
    [allowedCharacters addCharactersInString:@":./"];  //allow arbitrary characters

    if([string rangeOfCharacterFromSet:allowedCharacters.invertedSet].location == NSNotFound){

        return YES;

    }

    return NO;

}

- Brody Robertson

Answer 3

这是方法：

    - (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
    {
        // Only characters in the NSCharacterSet you choose will insertable.
        NSCharacterSet *invalidCharSet = [[NSCharacterSet characterSetWithCharactersInString:@"abcdefgABCDEFG"] invertedSet];
        NSString *filtered = [[string componentsSeparatedByCharactersInSet:invalidCharSet] componentsJoinedByString:@""];
        bool cond1 = [string isEqualToString:filtered];

     if (textField.text.length >= 10 && range.length == 0){
          return NO;
     }else{
          return (cond1);
     }

    }

- Resh32

---

我很快地写了这个，但是想法是要检查这两个条件是否都符合。 - Resh32

如果 (cond1) 返回 YES; 否则返回 NO - 为什么不直接使用 return (cond1) 呢？这总是让我感到困惑。 - Cyrille