Objective-c How to do validation on textField - ios

Question

I would like to prevent the user from not entering any data as well as entering only spaces. So basically there must at least be one character without a space. Then I would also like to remove any spaces at the beginning of the word so the first letter is a character that is not a space.
edit
the user must enter something and if the user enters a few spaces before it then I want to trim those spaces. I also want to prevent the user from just entering spaces.
Example
if the user enter's a name and surname like " James Dean" I would like to take the first space away but not the second space between James and Dean.

Answer 1

Set your UIViewController to be your destination UITextField's delegate and implement this method:
- (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

try like this may be it helps to you,here is my code
- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range
replacementString:(NSString *)string{
if([text.text length]==0){
if([string isEqualToString:#" "]){
return NO;
}
}
return YES;
}
By placing this code user won't enter space as a first letter but it accepts the space in the middle of the string.

Answer 3

I'll give you a hint for the first part.
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;
}