The Project File and Its Dependents in Xcode

The first item in the Project navigator (Command-1) represents the project itself. (In the Empty Window project that we created earlier in this chapter, it is called Empty Window.) Hierarchically dependent upon it are items that contribute to the building of the project. Many of these items, including the project itself, correspond to items on disk in the project folder.

To survey this correspondence, let’s examine the project folder in the Finder simulta‐ neously with the Xcode project window. Select the project listing in the Project navigator and choose File → Show in Finder (Figure 6-7).

The Finder displays the contents of your project folder. The most important of these is Empty Window.xcodeproj. This is the project file, corresponding to the project listed in the Project navigator. All Xcode’s knowledge about your project — what files it consists of and how to build the project — is stored in this file. To open a project from the Finder, double-click the project file. Alternatively, you can drag the project folder onto Xcode’s icon (in the Finder, in the Dock, or in the application switcher) and Xcode will locate the project file and open it for you; thus, you might never need to open the project folder at all!

 Let’s consider how the groups and files displayed hierarchically down from the project in the Project navigator correspond to reality on disk as portrayed in the Finder (Figure 6-7). (Recall that group is the technical term for the folder-like objects shown in the Project navigator.) Groups in the Project navigator don’t necessarily correspond to folders on disk in the Finder, and folders on disk in the Finder don’t necessarily correspond to groups in the Project navigator:

• The Empty Window group corresponds directly to the Empty Window folder on disk. Files within the Empty Window group, such as AppDelegate.m, correspond to real files on disk that are inside the Empty Window folder. If you were to create additional code files (which, in real life, you would almost certainly do in the course of developing your project), you would likely put them in the Empty Window group in the Project navigator, and they, too, would then be in the Empty Window folder on disk. (That, however, is not a requirement; your files can live anywhere and your project will still work fine.)
  Similarly, the Empty Window Tests group corresponds to the Empty Window Tests folder on disk, and the file Empty_WindowTests.m listed inside the Empty Window Tests group lives inside the Empty Window Tests folder.
  These two group–folder pairs correspond to the two targets of your project. I’ll talk in the next section about what a target is. There is no law requiring that a target have a corresponding group in the Project navigator and a corresponding folder in the project folder, but the project template sets things up that way as an organiza‐ tional convenience: it clarifies the project’s structure in the Project navigator, and it prevents a lot of files from appearing at the top level of the project folder.
  
  
• The Supporting Files group inside the Empty Window group, on the other hand, corresponds to nothing on disk; it’s just a way of clumping some items together in the Project navigator, so that they can be located easily and can be shown or hidden together. The things inside this group are real, however; you can see that the four files Empty Window-Info.plist, InfoPlist.strings, main.m, and Empty Window- Prefix.pch do exist on disk — they’re just not inside anything called Supporting Files. (The Supporting Files group inside the Empty WindowTests group is similar.)
  
  
• Two files in the Empty Window group, InfoPlist.strings and Main.storyboard, ap‐ pear in the Finder inside folders that don’t visibly correspond to anything in the Project navigator: Main.storyboard, on disk, is inside a folder called Base.lproj, and InfoPlist.strings, on disk, is inside a folder called en.lproj. 
  
  
• The item Images.xcassets in the Project navigator corresponds to a specially struc‐ tured folder Images.xcassets on disk. This is an asset catalog (new in Xcode 5); you add images to the asset catalog in Xcode, which maintains that folder on disk for you. This makes it easy for you to have multiple related images, such as app icons of different sizes, without having to see them all listed directly in the Project navi‐ gator. 
  
  You may be tempted to find all this confusing. Don’t! Remember what I said about not involving yourself with the project folder on disk in the Finder. Keep your attention on the Project navigator, make your modifications to the project there, and all will be well.
  Feel free, as you develop your project and add files to it, to add further groups. The purpose of groups is to make the Project navigator work well for you. They don’t affect how the app is built, and by default they don’t correspond to any folder on disk; they are just an organizational convenience within the Project navigator. To make a new group, choose File → New → Group. To rename a group, select it in the Project navigator and press Return to make the name editable. For example, if some of your code files have to do with a login screen that your app sometimes presents, you might clump them together in a Login group. If your app is to contain some sound files, you might put them into a Sounds group. And so on.
  The things in the Frameworks group and the Products group don’t correspond to any‐ thing in the project folder, but they do correspond to real things that the project needs to know about in order to build and run:
  
  Frameworks
  This group, by convention, lists frameworks (Cocoa code) on which your code depends. Frameworks exist on disk, but they are not built into your app when it is constructed; they don’t have to be, because they are present also on the target device (an iPhone, iPod touch, or iPad). Instead, the frameworks are linked to the app, meaning that the app knows about them and expects to find them on the device when it runs. Thus, all the framework code is omitted from the app itself, saving considerable space.
  (Starting in Xcode 5, the new modules feature permits frameworks to be linked to your code without being listed here. I’ll talk about modules at the end of this chap‐ ter.)
  
  Products
  
  This group, by convention, automatically holds a reference to the executable bundle generated by building a target.