Start-up function of a program

I want to execute a code snippet when program start-up, so what is the start-up function of iOS program?

For Android program, the start-up function is onCreate as below

public class HelloWorld extends Activity {
   public void onCreate(Bundle 开发者_StackOverflowsavedInstanceState) {
       ...

How about iOS program?

Thanks

In iOS you use the UIApplicationDelegate protocol in order to be informed of application lifecycle events (startup, suspend, shutdown, etc.):

@interface MyAppDelegate : NSObject <UIApplicationDelegate> {
}
@end

@implementation MyAppDelegate
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions {
    //start-up code here

    return YES;
}
@end

Assuming that you are using XCode for your iOS project, it will have created a default UIApplicationDelegate class for you. All you need to do is find it and edit the application:didFinishLaunchingWithOptions: method to your liking.

The main function is called to begin the program. It is found in main.m in the templates in Xcode. You can also use __attribute__((constructor)) to mark a function for execution before the program begins, or create a +load or +initialize method on a class. +load methods are called when a class is loaded into memory, before the program begins, but not everything will be loaded at that point. +initialize is called automatically before any other method in the class it is defined in, after the program starts.