interface - Multi inheritance for IOS -


i want create class can inherit 2 custom class. have idea please? please see below example:

first class:

@interface uizoomableview : uiview {     uitapgesturerecognizer *_tapgesturerecognizer; }

and implementation:

- (void)ondoubletap:(uitapgesturerecognizer *)sender {     cgsize newsize;     cgpoint centerpoint = self.center;     if ([self issmall])     {         newsize = [self bigsize];     }     else     {         newsize = [self smallsize];     }      [uiview animatewithduration:0.3 animations:^{         self.size = newsize;         self.center = centerpoint;     }]; }

second class:

@interface uidraggableview : uiview      uipangesturerecognizer *_pangesturerecognizer;  @end

implementation:

- (void)handlepan:(uipangesturerecognizer*)sender {     .. }

i want create custom view can zoomable , draggable. have idea please? (without copy code..)

i think protocols want default value base classes? how can implement using protocol or protocols.

thanks response!

objective-c doesn't support multiple inheritance. use protocol, composition , message forwarding achieve same result.

a protocol defines set of methods object must implement (it's possible have optional methods too). composition technique of include reference object , calling object when it's functionality required. message forwarding mechanism allows objects pass messages onto other objects, example, object included via composition.

apple reference:

so, in case composition might solution, below example code

@interface classa : nsobject { }  -(void)methoda;  @end  @interface classb : nsobject { }  -(void)methodb;  @end  @interface myclass : nsobject {   classa *a;   classb *b; }  -(id)initwitha:(classa *)ana b:(classb *)ab;  -(void)methoda; -(void)methodb;  @end  @implementation myclass  -(id)initwitha:(classa *)ana b:(classb *)ab {     = ana ;     b = ab ; }  -(void)methoda {     [a methoda] ; }  -(void)methodb {     [b methodb] ; }  @end

if don't want implement methods classa , classb in myclass, can use message forwarding in myclass handle method invocations. below works fine long classa , classb not have common methods.

@implementation myclass  -(id)initwitha:(classa *)ana b:(classb *)ab {     = ana ;     b = ab ; }  //this method called, when myclass can not handle method -(void)forwardinvocation:(nsinvocation *)aninvocation {     if ([a respondstoselector:[aninvocation selector]])         [a invokewithtarget:someotherobject];     else if ([b respondstoselector:[aninvocation selector]])         [b invokewithtarget:someotherobject];     else         [super forwardinvocation:aninvocation]; }  @end

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