How can I make my framework's code automatically run when the app launches?

Objective-C classes derived from NSObject have the class methods +initialize and +load.

The first one is run the first time you send a message to the class, so it is of no use unless you do something in -application:didFinishLaunchingWithOptions: as you mentioned.

The second one is called exactly once for each class in the app, even if it is not used:

Discussion

The load message is sent to classes and categories that are both dynamically loaded and statically linked, but only if the newly loaded class or category implements a method that can respond.

The order of initialization is as follows:

1. All initializers in any framework you link to.

2. All +load methods in your image.

3. All C++ static initializers and C/C++ attribute(constructor) functions in your image.

4. All initializers in frameworks that link to you.

In addition:

• A class’s +load method is called after all of its superclasses’ +load methods.

• A category +load method is called after the class’s own +load method.

In a custom implementation of load you can therefore safely message other unrelated classes from the same image, but any load methods implemented by those classes may not have run yet.

Source: Apple's Official Documentation (NSObject Class Reference).

Perhaps you could place your initialization logic there.

If you are using swift, I don't know of any method.