I often use this statement for extending class without needs of writing a whole separate file. Supposing ClassFromFramework is a class being part of a framework included in libr
You can make a new subclass, and override methods, but all new classes must be in their own .h & .m files. That's how Obj-C operates. In this case, it would make sense to have the additional files.
You can also call the parent method with the word super. This is done all the time when subclassing a ViewController, such as in viewDidLoad.