A build only device cannot be used to run this target

Question

I get this error when I trying to test an app.

A build only device cannot be used to run this target.

No supported iOS devices are available

Answer 1

You are building for Xcode's "Build Only Device", which is compiling the app. for the ARM processor (whereas compiling for the simulator targets the Intel CPU on your Mac.)

Plug in a device and select it from the active scheme popup, or, select one of the simulators and you should be good to go.