Importing header in objective c

Question

In Objective-c when we using object of one class into another class by convention we should forward declare the class in .h file, i.e. @class classname;. And sh

Answer 1

You are correct that importing the header in the .h makes like easier (in the short run). The reason not to do this and import it in the implementation file (.m) is to prevent name pollution, where all the names in the imported header are available when someone imports your header. Instead, by importing your header only your functions/classes shuld be imported and the rest at the implementation

Also, if you import the header in the .h, that means every code that imported your header will have to be recompiled when the 3rd-party header changes, even if nothing has changed in your header explicitly. Forward declaration avoids this problem and forces only those implementation (.m) files to be recompiled that actually make use of the 3rd-party header