Objective-C polymorphism-use of dynamic type IDs

Reproduced in: http://www.cnblogs.com/54007/archive/2011/02/11/1951355.html

In C #, we use interfaces to implement polymorphism. For example, the interface iob defines a method F. There are two classes A and B that implement the IOB interface.

Iob item = new ();

Item. F (); // The execution is a.f ();

Item = new B ();

Item. F (); // The executed B. F ();

In objective-C, the meaning of the interface is very different from that of C #, and cannot be used in this way.

So how can we achieve similar results. This is a special type ID. See the following code snippet. Note: Both fraction and complex contain the print method.

 

# Import "fraction. H "# import" complex. h "int main (INT argc, char * argv []) {ngutoreleasepool * Pool = [[ngutoreleasepool alloc] init]; Id datavalue; // defines an ID type variable fraction * F1 = [[fraction alloc] init]; complex * C1 = [[complex alloc] init]; [F1 setto: 2 over: 5]; [C1 setreal: 10.0 andimaginary: 2.5]; // first datavalue gets a fractiondatavalue = F1; [datavalue print]; // call the print method of fraction // now datavalue gets a complex numberdatavalue = C1; [datavalue print]; // call complex's print method [C1 release]; [F1 release]; [pool drain]; return 0 ;}