Objective-c class create methods -

let's have class base.

@inerface base : nsobject { } +(id) instance; @end  @implementation base +(id) instance {     return [[[self alloc] init] autorelease]; } -(id) init { ... } @end 

and have derived class derived.

@interface derived : base { } @end 

which reimplements init method.

now want create instance of derived class using class method +(id) instance.

id foo = [derived instance]; 

and foo base class.

how achieve foo derived class in case?

should reimplement class method derived classes ? (actually immplementation totally same).

is there more elegant way ?

when create instance using [derived instance], instance of class derived. try it. trick messaging self in instance method:

+(id) instance {     return [[[self alloc] init] autorelease]; } 

when send instance message base, self base. when send same message derived, self derived , therefore whole thing works desirable.