iOS中输入框设置指定字符输入的方法

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string {
 return [self validateNumber:string];
}
- (BOOL)validateNumber:(NSString*)number {
 BOOL res = YES;
 NSCharacterSet* tmpSet = [NSCharacterSet characterSetWithCharactersInString:@"0123456789"];
 int i = 0;
 while (i < number.length) {
 NSString * string = [number substringWithRange:NSMakeRange(i, 1)];
 NSRange range = [string rangeOfCharacterFromSet:tmpSet];
 if (range.length == 0) {
  res = NO;
  break;
 }
 i++;
 }
 return res;
}

#define NUMBER @"0123456789"

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
 NSCharacterSet *cs = [[NSCharacterSet characterSetWithCharactersInString:NUMBER] invertedSet];
 NSString *filtered = [[string componentsSeparatedByCharactersInSet:cs] componentsJoinedByString:@""];
 return [string isEqualToString:filtered];
}

#define LETTER @"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string
{
 NSCharacterSet *cs = [[NSCharacterSet characterSetWithCharactersInString:LETTER] invertedSet];
 NSString *filtered = [[string componentsSeparatedByCharactersInSet:cs] componentsJoinedByString:@""];
 return [string isEqualToString:filtered];
}

#define LETTER_NUMBER @"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789"

- (void)viewDidLoad {
 [super viewDidLoad];
 _myTextField.delegate = self;
 [[NSNotificationCenter defaultCenter]addObserver:self selector:@selector(textFiledEditChanged:) name:UITextFieldTextDidChangeNotification object:_myTextField];
}
- (BOOL)textFieldShouldReturn:(UITextField *)textField{
 [textField resignFirstResponder]; 
 //过滤非汉字字符
 textField.text = [self filterCharactor:textField.text withRegex:@"[^\u4e00-\u9fa5]"]; 
 if (textField.text.length >= 4) {
  textField.text = [textField.text substringToIndex:4];  
 }
 return NO;
}
- (void)textFiledEditChanged:(id)notification{
 UITextRange *selectedRange = _myTextField.markedTextRange;
 UITextPosition *position = [_myTextField positionFromPosition:selectedRange.start offset:0];
 
 if (!position) { //// 没有高亮选择的字
  //过滤非汉字字符
  _myTextField.text = [self filterCharactor:_myTextField.text withRegex:@"[^\u4e00-\u9fa5]"];
  
  if (_myTextField.text.length >= 4) {
   _myTextField.text = [_myTextField.text substringToIndex:4];
  }
 }else { //有高亮文字
  //do nothing
 }
}
- (NSString *)filterCharactor:(NSString *)string withRegex:(NSString *)regexStr{
 NSString *searchText = string;
 NSError *error = NULL;
 NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:regexStr options:NSRegularExpressionCaseInsensitive error:&error];
 NSString *result = [regex stringByReplacingMatchesInString:searchText options:NSMatchingReportCompletion range:NSMakeRange(0, searchText.length) withTemplate:@""];
 return result;
}
- (void)dealloc{
 [[NSNotificationCenter defaultCenter] removeObserver:self];
}

- (void)textViewDidChange:(UITextView *)textView{
 NSInteger number = [textView.text length];
 if (number > 300) {
  textView.text = [textView.text substringToIndex:300];
 }
}