Image change validation - objective-c

Question

I want to change the image in validation like if the text field is empty the image color is grey or if filled the circle is green color.
I have tried this in button action-
UIImageView *imgView = [[UIImageView alloc] initWithFrame:CGRectMake(10, 10, 100, 50)];
imgView.image = [UIImage imageNamed:#"a_image.png"];
imgView.contentMode = UIViewContentModeCenter;

Answer 1

Try this in your button action.
if (self.MyTextField.text.length!=0)
self.MyImageView.image=[UIImage imageNamed:#"redImage"];
else
self.MyImageView.image=[UIImage imageNamed:#"greenImage"];
If you want to change colour when user is typing in text field, use following delegate method of textfield to do any stuff.
-(void)textFieldDidBeginEditing:(UITextField *)textField;

Answer 2

UIImageView *imgView = [[UIImageView alloc] initWithFrame:CGRectMake(10, 10, 100, 50)];
if (textField.text.length == 0){
imgView.image = [UIImage imageNamed:#"firstImage.png"];
} else {
imgView.image = [UIImage imageNamed:#"secondImage.png"];
}

Answer 3

Should be pretty simple:
if (textField.text.length == 0){
//Do something if its empty
} else {
//Do something else if its not
}
EDIT: If you want to do this on the fly and not when they're done editing you could do something like:
- (void)viewDidLoad
{
[super viewDidLoad];
[self.textField addTarget:self action:#selector(textChanged) forControlEvents:UIControlEventEditingChanged];
}
- (void)textChanged
{
if (self.textField.text.length == 0) {
self.someVIew.backgroundColor = [UIColor grayColor];
} else if (self.textField.text.length > 5){
self.someVIew.backgroundColor = [UIColor redColor];
} else {
self.someVIew.backgroundColor = [UIColor greenColor];
}
}