ios - Objective-c 如何对 textField 进行验证

Question

我想防止用户不输入任何数据以及只输入空格。所以基本上必须至少有一个没有空格的字符。然后我还想删除单词开头的任何空格，所以第一个字母是一个不是空格的字符。

编辑

用户必须输入一些内容，如果用户在它之前输入几个空格，那么我想修剪这些空格。我还想防止用户只输入空格。

例子

如果用户输入像“James Dean”这样的名字和姓氏，我想拿走第一个空格，而不是 James 和 Dean 之间的第二个空格。

Answer 1

将您设置为您的UIViewController目的地并实施此方法：UITextFielddelegate

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

  // verify the text field you wanna validate
  if (textField == _nameTextField) {

    // do not allow the first character to be space | do not allow more than one space
    if ([string isEqualToString:@" "]) {
      if (!textField.text.length)
        return NO;
      if ([[textField.text stringByReplacingCharactersInRange:range withString:string] rangeOfString:@"  "].length)
        return NO;
    }

    // allow backspace
    if ([textField.text stringByReplacingCharactersInRange:range withString:string].length < textField.text.length) {
      return YES;
    }

    // in case you need to limit the max number of characters
    if ([textField.text stringByReplacingCharactersInRange:range withString:string].length > 30) {
      return NO;
    }

    // limit the input to only the stuff in this character set, so no emoji or cirylic or any other insane characters
    NSCharacterSet *set = [NSCharacterSet characterSetWithCharactersInString:@"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890 "];

    if ([string rangeOfCharacterFromSet:set].location == NSNotFound) {
      return NO;
    }

  }

  return YES;
}

Answer 2

试试这样可能对你有帮助，这是我的代码

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range 

    replacementString:(NSString *)string{
        if([text.text length]==0){
        if([string isEqualToString:@" "]){
            return NO;
        }
        }
        return YES;
    }

通过放置此代码，用户不会输入空格作为第一个字母，但它接受字符串中间的空格。

Answer 3

我会在第一部分给你一个提示。

NSString *tempname1 = [self.textField.text stringByReplacingOccurrencesOfString:@" " withString:@""];

BOOL thereAreJustSpaces = [tempname1 isEqualToString:@""];

Answer 4

-(void)removeSpacesFromTextFields:(id) sender {
    NSString *trim = [self.FNTextField.text stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]];
    if ([trim length] == 0) {
      self.FNTextField.text = @"";
    }
}

Answer 5

Try this, If you want to prevent space in your text field.

- (void)viewDidLoad
{
 [[NSNotificationCenter defaultCenter]addObserver:self selector:@selector(checkSpace:) name:UITextFieldTextDidChangeNotification  object:textfield];

}
 -(void)checkSpace:(NSNotification *)notification
{

  str = [textfield.text stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]] ;
 textfield.text=str;
}