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1). Info.plist : iOS通过它和app交互
The Info.plist file contains metadata about your app, which the system uses to interact with your app.
The Information Property List File
Xcode uses information from the General, Capabilities, and Info tabs of your project to generate an information property list (Info.plist) file for your app at compile time. The Info.plist file is a structured file that contains critical information about your app’s configuration. It is used by the App Store and by iOS to determine your app’s capabilities and to locate key resources. Every app must include this file.
Whenever possible, use the General and Capabilities tabs to specify the configuration information for your app. Those tabs contain the most common configuration options available for apps. If you do not see a specific option on either of those tabs, use the Info tab.
2). A declaration of the app’s required capabilities :
The App Store uses this information to determine whether or not a user can run your app on a specific device.
3). app bundle
An iOS app bundle contains the app executable file and supporting resource files such as app icons, image files, and localized content.
For more information about the structure of an iOS app bundle, see Bundle Programming Guide. For information about how to load resource files from your bundle, see Resource Programming Guide.
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The UIApplication object manages the event loop and other high-level app behaviors. It also reports key app transitions and some special events (such as incoming push notifications) to its delegate, which is a custom object you define. Use the UIApplication object as is—that is, without subclassing.
The app delegate is the heart of your custom code. This object works in tandem with the UIApplication object to handle app initialization, state transitions, and many high-level app events. This object is also the only one guaranteed to be present in every app, so it is often used to set up the app’s initial data structures.
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View controller objects manage the presentation of your app’s content on screen. A view controller manages a single view and its collection of subviews. When presented, the view controller makes its views visible by installing them in the app’s window. The UIViewController class is the base class for all view controller objects. It provides default functionality for loading views, presenting them, rotating them in response to device rotations, and several other standard system behaviors. UIKit and other frameworks define additional view controller classes to implement standard system interfaces such as the image picker, tab bar interface, and navigation interface. For detailed information about how to use view controllers, see View Controller Programming Guide for iOS. |
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A UIWindow object coordinates the presentation of one or more views on a screen. Most apps have only one window, which presents content on the main screen, but apps may have an additional window for content displayed on an external display. To change the content of your app, you use a view controller to change the views displayed in the corresponding window. You never replace the window itself. In addition to hosting views, windows work with the UIApplication object to deliver events to your views and view controllers. |
参考：App Programming Guide for iOS