在 UITextView 中防止小写 [英] Prevent lower case in UITextView

问题描述

我试图阻止用户在 UITextView 中输入任何小写字符.

I am trying to prevent the user from entering any lowercase characters into a UITextView.

我创建了一个可接受字符的#define 字符集

I have created a #define character set of acceptable characters

#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.

Now I would like to know how to use this to return no in the UITextView delegate when the user tries to enter a character that dose not match my VALID_CHARACTERS.

推荐答案

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

I suggest using textView:shouldChangeTextInRange:replacementText: and returning NO if the replacement text contains invalid characters.

编辑(回复您的评论):

Edit (in response to your comment):

// 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]);

}

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