I'm trying to define launch images. Probably only one image is missing.
I'm following the instructions from this site Create launch images in different sizes for different devices
So I have 7 images with the required size. But when I drag them to LaonchImages sheet it requires 8 images...the one that is missing is called "iPhone Portrait 2x" and according to the details pane I found its size 640x960 and I added it.
sill I'm getting the error - and the compilation fails...
Select your project, go to Build Settings, search for AppIcon-2 and change it into AppIcon and you will be fine.
Select project file and then select target in question. In General tab there is in app icons and launch images launch image source should be "Use assets category"
My LaunchImage file had been deleted and I had to add a new one in my xcassets.
Go to your images.xcassets. If there is no LaunchImage listed on the left, click the plus button at the bottom and navigate to new iOS launch image. 
In my case the problem was solved by removing the reference to Images.xcassets and then add it to the project again.
I'm not sure what caused the problem, but it may have something to do with the fact that I moved the assets "file" from one Xcode group to another, which would be weird as the file's path remained the same, but that was also the only thing I did with the file...
We had our Asset Catalog Launch Image Set Name set in our project target. After removing this from the target and instead setting it in our project it compiled fine.
