assignment in prepareForSegue false - ios

Question

I want to send a image to next scent.but failed.
here is my code
- (void) prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
NSLog(#"prepareForSegue start");
NSLog(#"count is %d",count);
//bigStyle1 is a NSArray,full of UIImage
//bigImage is a UIImageView outlet
if ([bigStyle1 objectAtIndex:count]==nil) {
NSLog(#"no array image");
}
viewController3.bigImage.image=[bigStyle1 objectAtIndex:count];
if (viewController3.bigImage.image==nil) {
NSLog(#"no controller image");
}
NSLog(#"secondToThird");
NSLog(#"prepareForSegue end");
}
here is Xcode's log
2013-03-12 15:15:38.683 animation[1876:f803] prepareForSegue start
2013-03-12 15:15:50.825 animation[1876:f803] count is 0
2013-03-12 15:17:10.829 animation[1876:f803] no controller image
It seems that the problem is in assignment of image.Why assignment failed?
UPDATE
viewController3 isn't nil.But bigImage is nil.I don't know why.I actually connect bigImage to the image view

Answer 1

I suspect that you intend viewController3 to be the destination of the segue. In that case, you should be setting it like this:
viewController3 = segue.destinationViewController;
I further suspect that viewController3.bigImage is a UIImageView. If so, you have a problem because viewController3 hasn't loaded its view hierarchy by the time the system sends prepareForSegue:sender:, so viewController3.bigImage hasn't been set yet. It's nil, and setting a property on nil does nothing (with no warning or error message).
It would be better to give viewController3 an image property directly, and store the image on that property. Then, in viewController3's viewDidLoad method, copy the image from that property to self.bigImage.image.
Alternatively, you can cheese it by forcing viewController3 to load its view in prepareForSegue:sender: just by asking it for its view:
[viewController3 view]; // forces it to load its view hierarchy if necessary
viewController3.bigImage.image = [bigStyle1 objectAtIndex:count];