I found out a way to resize the height of a text field according to the text inside it and also arrange a label below it based on the height of the text field! Here is the code.
UITextView *_textView = [[UITextView alloc] initWithFrame:CGRectMake(10, 10, 300, 10)];
NSString *str = @"This is a test text view to check the auto increment of height of a text view. This is only a test. The real data is something different.";
_textView.text = str;
[self.view addSubview:_textView];
CGRect frame = _textView.frame;
frame.size.height = _textView.contentSize.height;
_textView.frame = frame;
UILabel *lbl = [[UILabel alloc] initWithFrame:CGRectMake(10, 5 + frame.origin.y + frame.size.height, 300, 20)];
lbl.text = @"Hello!";
[self.view addSubview:lbl];