If I release the object that's holding a reference to the variable that I need to release, is that sufficient? Or must I release at every level of the containment hierarchy? I fear that my logic comes from working with a garbage collector for too long.

For instance, I assigned to this property of a UIPickerView instance by hand instead of using IB

@property(nonatomic, assign) id<UIPickerViewDelegate> delegate

Since it's an assign property, I can't just release the reference after I assign it. When I finally release my UIPickerView instance, do I need to do this:

[singlePicker.delegate release];
[singlePicker release];

or is the second line sufficient?

Also: Are these assign properties the norm, or is that mostly for Interface Builder? I thought that retain properties were the normal thing to expect.