Main.storyboard: Scene is unreachable due to lack of entry points and does not have an identifier for runtime access via -instantiateViewControllerWithIdentifier:.

I'm using Xcode 6.1 on Mac OS X Mavericks v10.9.5. The warning appeared when I have more than one view controllers in my story board.

To remove the warning, I set the Storyboard ID (in the Identity Inspector) for all the view controllers, which are not root view controller. The root view controller is the one with the Is Initial View Controller property checked (in Attributes Inspector).

The storyboard ID identifies the view controller within a storyboard. Storyboard ID is used when you want to programmatically access a view controller for some reasons such as switching to another view.

Got black screen when starting simulator

I'm using Xcode v6.1 on Mac OS X Mavericks v10.9.5. I'm new to iOS so i'm developing a simple app for learning. It's using two frameworks such as UI Kit and Foundation. When running my app in simulator, sometimes it worked but some other times i just showed black screen as shown in the image below.

As you can see on the title bar of the simulator, the app was built and run on iPhone 4s. Then I changed the destination device to iPhone 5 or newer, it worked. I don't know why but perhaps my application is using some classes or libraries which are not supported by iPhone 4s.

To change the running device, click on Product menu then Destination and select iPhone 5. After that, clean the project (command+shift+K), and build and run (command+R) it again.