如何限制UITextField中的字符

Question

我有UITextField以下限制 - 字符只能是数字,如下面的方法.我还想将最大字符数限制为3位数.如何修改我的方法来做到这一点？

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
NSCharacterSet *aCharacterSet = [NSCharacterSet characterSetWithCharactersInString:@"0123456789"];
for (int i = 0; i < [string length]; i++) {
    unichar aCharacter = [string characterAtIndex:i];
    if ([aCharacterSet characterIsMember:aCharacter]) {
        return YES;
    }
}

NSUInteger newLength = self.textField.text.length + string.length - range.length;
return (newLength > 3) ? NO : YES;
}

Answer 1

o限制代码下方的文本字段使用.

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
     NSString *newString = [textField.text stringByReplacingCharactersInRange:range withString:string];    
        return !([newString length] > 3);

}

Answer 2

尝试这个：

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
NSCharacterSet *aCharacterSet = [[NSCharacterSet decimalDigitCharacterSet] invertedSet];
NSString *filtered =  [[string componentsSeparatedByCharactersInSet:aCharacterSet] componentsJoinedByString:@""];
if ((textField.text.length >2) && (!(string.length == 0)))
            return NO;
        else
            return [string isEqualToString:filtered];
}