アプリ終了/中断時にデータを保存し、起動時にデータを戻す

viewWillAppear:(BOOL)animatedが起動時に呼ばれ、viewWillDisappear:(BOOL)animatedが起動時に呼ばれます。

- (void)viewWillAppear:(BOOL)animated
{
  NSString *string = [[NSUserDefaults standardUserDefaults] stringForKey:@"MyString"];
  textField.text = string;
}
 
- (void)viewWillDisappear:(BOOL)animated
{
  NSString *string = textField.text;
  [[NSUserDefaults standardUserDefaults] setObject:string forKey:@"MyString"];
}