Having the above mentioned use-case in mind, how can I retrieve the URL used to start the app ( if any ), OR, to intercept the 'openUrl' method implemented by the Applications AppDelegate ?
You can create your own class that implements the UIApplicationDelegate protocol. In your SDK's start-up code (which the user will have to call early in something like application:willFinishLaunchingWithOptions:), instantiate it, and replace the main UIApplication object's delegate with your custom object.
Your custom object is now the application delegate instead of theirs.
Prior to setting the UIApplication object's delegate, set your class's delegate to the current UIApplication delegate so that you can forward any messages back to their application delegate object.
No swizzling required.
This is actually quite simple, having the SDK linked as a DyLib and the main object initialized in a "attribute((constructor))" section, the following is what needed:
IMP g_originalSetDelegate = nil;
IMP g_originalOpenUrl = nil;
BOOL swizzle_openUrl(id self, SEL _cmd, UIApplication* application, NSURL* url, NSString* sourceApplication, id annotation) {
// TBD: Do your magic
return ((BOOL(*)(id,SEL,UIApplication*,NSURL*,NSString*,id))g_originalOpenUrl)(self, _cmd, application, url, sourceApplication, annotation);
}
void swizzle_setDelegate(id self, SEL _cmd, id delegate) {
((void(*)(id,SEL,id))g_originalSetDelegate)(self, _cmd, delegate);// Call the original method
auto method = class_getInstanceMethod([delegate class], @selector(application:openURL:sourceApplication:annotation:));
g_originalOpenUrl = method_getImplementation(method);
method_setImplementation(method, (IMP)swizzle_openUrl);
}
-(id)init {
auto method = class_getInstanceMethod([UIApplication class], @selector(setDelegate:));
g_originalSetDelegate = method_getImplementation(method);
method_setImplementation(method, (IMP)swizzle_setDelegate);
...
}