xcode "The file couldn't be opened" [closed]

I have reinstalled El Capitan, xcode 7.2 and the necessary libraries (ionic, gulp, ..) and everything works fine now.

Curious...

I had the same problem, and it was caused by a different format of Xcode project file. If the project is compiled with the old Xcode, the new one cannot not open it.

I suggest you to remove any build file to make sure that next time project is really compiled, and if problem persist, remove also the old version of Xcode, because it looks like it is the one used to compile the project.

Alternatively, maybe ionic CLI has some option to select which Xcode it should use.

2 possible solutions:

1. Ionic configuration value

It seems that somewhere in your project, a config value makes ionic still think you use XCode 6 because you were using it before, and so continues to generate the project file accordingly.
What happens if you start over, in another directory, from a starter project file:

ionic start myApp tabsionic prepare ios

Can you open the generated XCode project file?If yes, I suggest you to copy over this starter project all the files from your original project.

2. Update nodeJs to the latest version

I see you use node 4.x.x, try updating to 5.x.x.