The iPhone/iPad application build process is a two step process:
When “Build” is hit on “Build settings” dialog only the first step is accomplished. Hitting “Build and Run” performs both steps. If in the project save dialog the user selects an already existing folder an alert is displayed. Currently there are two Xcode project generation modes to select:
If Cmd+B is hit then the automatic build and run process is invoked and the latest used folder is assumed as the build target. In this case append mode is assumed as default.
Note: Step one above can be performed on a PC or a Mac. Only a Mac can perform Step two. This means to get a Unity project running on an iDevice you will need to have a Mac.
Once Unity has been used to build the Xcode project it is possible to perform the build and run from the command line. After the editor has built the Xcode project do the following from the terminal:
unity$ xcodebuild test -destination "platform=iOS,id=400d20d00baf8d4997b47be0416cf5c44dd2d3bc" -scheme Unity-iPhone
Note that 400d20d00baf8d4997b47be0416cf5c44dd2d3bc in the command line example above is the ID of the iDevice that will run the project. You will need to determine your device ID using the Window > Devices menu in Xcode.