在 UITextView 中防止小写

Question

我试图阻止用户在 UITextView 中输入任何小写字符。

我创建了一个可接受字符的#define 字符集

#define VALID_CHARACTERS @"ABCDEFGHIJKLMNOPQRSTUVWYXZ1234567890"

现在我想知道当用户尝试输入与我的 VALID_CHARACTERS 不匹配的字符时，如何使用它在 UITextView 委托中返回 no。

Answer 1

最简单的解决方案：

使用UITextView委托方法：

- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text;

方法实现：

- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text
{
    if ([text rangeOfCharacterFromSet:[NSCharacterSet lowercaseLetterCharacterSet]].location != NSNotFound) {
        textView.text = [textView.text stringByReplacingCharactersInRange:range withString:text.uppercaseString];
        return NO;
    }

    return YES;
}

Answer 2

如果替换文本包含无效字符，我建议使用textView:shouldChangeTextInRange:replacementText: 并返回 NO。

编辑（回应您的评论）：

// Goal: Remove all the non-valid characters from the replacement string
// then see if the string is the same as the original replacement string;
// if it is, then the string is valid and return YES, else return NO

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

    // First step - define a character set with the valid characters
    NSMutableCharacterSet *validSet = [NSMutableCharacterSet characterSetWithCharactersInString:VALID_CHARACTERS];

    // Second step - define a character set with the inverse, i.e invalid characters
    NSCharacterSet *invalidSet = [validSet invertedSet];

    // Then remove all invalid characters by separating the string into components
    // separated by the invalid characters using componentsSeparatedByCharactersInSet:
    // and then rejoining the set using componentsJoinedByString: so that it now only
    // contains valid characters
    NSString *filteredString = [[string componentsSeparatedByCharactersInSet:invalidSet] componentsJoinedByString:@""];

    // Compare that filtered string with the original string then see if its
    // the same as the replacement string; if the same (i.e. no invalid characters
    // have been removed), return yes, if not, return no.
    return ([filteredString isEqualToString:string]);

}

Answer 3

要限制文本视图的可能输入字符，请实现文本视图 像这样的委托：

- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text
{    
    static NSString *validChars = @"ABCDEFGHIJKLMNOPQRSTUVWYXZ1234567890\n";
    NSCharacterSet *validSet = [NSCharacterSet characterSetWithCharactersInString:validChars];
    if ([[text stringByTrimmingCharactersInSet:validSet] length] > 0)
        return NO;
    return YES;
}

validChars 中的\n 用于返回键（您可能希望也可能不希望允许）。

按照 cmets 的建议，您可以将小写字母转换为大写字母 自动：

- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text
{    
    text = [text uppercaseString];
    static NSString *validChars = @"ABCDEFGHIJKLMNOPQRSTUVWYXZ1234567890\n";
    NSCharacterSet *validSet = [NSCharacterSet characterSetWithCharactersInString:validChars];
    if ([[text stringByTrimmingCharactersInSet:validSet] length] > 0)
        return NO;
    textView.text = [textView.text stringByReplacingCharactersInRange:range withString:text];
    return NO;
}

要允许其他语言的大写字母和数字，请更改 validSet 的定义为

NSMutableCharacterSet *validSet = [NSMutableCharacterSet uppercaseLetterCharacterSet];
[validSet formUnionWithCharacterSet:[NSCharacterSet decimalDigitCharacterSet]];
[validSet formUnionWithCharacterSet:[NSCharacterSet newlineCharacterSet]];

由于文本视图委托被频繁调用，您可以通过以下方式改进它 使用 GCD 只计算一次有效字符集：

- (BOOL)textView:(UITextView *)textView shouldChangeTextInRange:(NSRange)range replacementText:(NSString *)text
{
    static NSCharacterSet *validSet;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        NSMutableCharacterSet *tmpSet = [NSMutableCharacterSet uppercaseLetterCharacterSet];
        [tmpSet formUnionWithCharacterSet:[NSCharacterSet decimalDigitCharacterSet]];
        [tmpSet formUnionWithCharacterSet:[NSCharacterSet newlineCharacterSet]];
        validSet = [tmpSet copy];
    });
    text = [text uppercaseString];
    if ([[text stringByTrimmingCharactersInSet:validSet] length] > 0)
        return NO;
    textView.text = [textView.text stringByReplacingCharactersInRange:range withString:text];
    return NO;
}