objective c - why most of the objects we create in iphone are pointers

Question

why most of the objects we create in iphone are pointers..? like i create NSString *str, NSMutableDictionary *dict.. etc

Answer 1

Short Answer
Because Objective-C objects can only be allocated on the heap and manipulated as pointers.

Long Answer
Objective-C requires that classes be allocated on the heap and manipulated as pointers, because polymorphism requires the use of pointers, since the pointer to an interface will always have the same size, while different implementations of the interface may have different sizes. In C++, one can use both automatic (stack) and dynamic (heap) storage for classes; however, in the former case, one must beware of slicing (when a derived type is assigned to a base type, resulting in the object losing the content that makes it the derived type instead of the base type), and using pointers only as in Obj-C eliminates this potential pitfall. Additionally, allowing stack-allocated objects complicates the reference counting scheme that Objective-C has in place, and since stack-allocated objects live only in the scope in which they are created, one usually allocates objects on the heap, anyway, and so there would be marginal benefit in supporting objects as stack-allocated values. As a side note, I should also mention that both in Java and in C#, objects are similarly constrained to heap only allocation.