Weird in my UIImagePickerController with camera

I met a problem on using camera by scratch on iphone. Other people's code just run fine on my 3GS, but my code doesn't.

When I implemented a UIViewController controll开发者_Python百科er, and I add the following code in viewdidload:

UIImagePickerController *picker = [UIImagePickerController alloc] init];
picker.source = UIImagePickerControllerSourceTypeCamera;
picker.delegate = self; //Previously added all the delegate properly
[self presentModalViewController:picker animated:YES];

Nothing comes out. I checked in the debugger, it shows that the picker is allocated, but here is the major difference between my and success one.

picker._imagepickerflag.visible = 0;  //others show 1;
picker.UINavigationController._containerView: 0x0 ;  // others have value.

Can anyone help me on this, is there something wrong?

Thank you.

UIImagePickerController *picker = [UIImagePickerController alloc] init];

Above code is wrong. It should be

UIImagePickerController *picker = [[UIImagePickerController alloc] init];

This below is also wrong.

picker.source = UIImagePickerControllerSourceTypeCamera;

it should be

picker.sourceType = UIImagePickerControllerSourceTypeCamera;

And you should release it once it has been presented.

[picker release];

Hope that helps.