When I recently did some programming while riding in the commute train, I added an new image view, added an outlet using the Assistant editor of Xcode 5 and started to test my program. All worked well, I added a few changes and had to hop off the train.
Some hours later I continued testing and was surprised to see a black window instead of my app. I could not remember what I had changed last time. Could it be, that I had made mistakes in the connection of the scenes? Did not look like so. Did I make a mistake in the code? No evidence for that.
Then I finally saw it: Instead of putting the button to hidden, I had put my image view to hidden. I had connected the whole view, instead of connecting the button only – without noticing it. This meant, I had set the view that was meant to be the background to hidden and thus I had a black view into the endless dark black hole of the background behind the background.