iphone. making UITextView but won't make it visible

@interface SomeViewController : UIViewController <UITextViewDelegate>
 
 @property (retain, nonatomic) IBOutlet UIImageView *imageView;
 @property (nonatomic, retain) UIImage *image;
 
 @property (nonatomic, retain) IBOutlet UITextView *textView;
 

I need textview(editable) in my view controller.

so I set protocol , then textView to delegate my file's owner, done.

and also, IB to the file's owner, too. (I don't know, is it unnecessary?)

And my .m file.... viewDidLoad..

_textView = [[UITextView alloc]init];
 [_textView setFrame:CGRectMake(8, 110, 304, 82)];
 [_textView setFont:[UIFont boldSystemFontOfSize:12]];
 _textView.editable = YES;
 //[textView setText:@"hdgffgsfgsfgds"];// if uncommented, this actually visible...
 
 [self.view insertSubview:_textView atIndex:2];
 

So far, it's working. But I want these methods to run...

- (void)textViewDidChange:(UITextView *)textView
 {
 
 
     if([_textView.text length] == 0)
     {
         _textView.text = @"Foobar placeholder";
         _textView.textColor = [UIColor lightGrayColor];
         _textView.tag = 0;
     }
 }
 

But after build, my textview is still empty.

What did I wrong?

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