Message Forwarding is not working (Objective-C) - ios

Question

I am writing a sample code in order to understand message forwarding in Objective C (iOS).
I have two classes (class A and class B). I want to create an instance of class B and set a class A instance variable to it. I am calling the Forward Invocation method (Message Forwarding) in the following code.
// ViewController.h
// TestInvocation
#import <UIKit/UIKit.h>
#interface ViewController : UIViewController
#end
// ViewController.m
// TestInvocation
#import "ViewController.h"
#import "TestInvocation.h"
#interface ViewController ()
#end
#implementation ViewController
- (void)viewDidLoad {
[TestInvocation testRun];
[super viewDidLoad];
}
#end
// TestInvocation.h
// TestInvocation
#import <Foundation/Foundation.h>
#interface TestInvocation : NSObject
{}
+(void)testRun;
#end
// TestInvocation.m
// TestInvocation
#import "TestInvocation.h"
#import "ClassB.h"
#import "ClassA.h"
#implementation TestInvocation
+(void)testRun
{
ClassB* diplomat = [[ClassB alloc] init];
NSLog(#"value = %d",[diplomat value]);// Error shows up here on running:
//No visible #interface for 'ClassB' declares the selector 'value'
}
#end
// ClassA.h
// TestInvocation
#import <Foundation/Foundation.h>
#interface ClassA : NSObject
{
int value;
}
#property(readwrite,assign) int value;
#end
// ClassA.m
// TestInvocation
#import "ClassA.h"
#implementation ClassA
#synthesize value;
#end
// ClassB.h
// TestInvocation
#import <Foundation/Foundation.h>
#interface ClassB : NSObject
{}
#end
// ClassB.m
// TestInvocation
#import "ClassB.h"
#import "ClassA.h"
#implementation ClassB
- (NSMethodSignature *)methodSignatureForSelector:(SEL)aSelector {
return [ClassA instanceMethodSignatureForSelector:aSelector];
}
-(void)forwardInvocation:(NSInvocation *)anInvocation
{
ClassA* negotiate = [[ClassA alloc] init];
negotiate.value = 15;
[anInvocation invokeWithTarget:negotiate];
}
#end
I am expecting the above code to work. But instead I get the following build time error:
ARC Semantic Issue
TestInvocation.m:19:35: No visible #interface for 'ClassB' declares the selector 'value'

Answer 1

Class B should have the property in interface at least.
But you can make it #dynamic in implementation if you want to call forwardInvocation.
#interface ClassB : NSObject
#property (readwrite, assign) int value;
#end
#implementation ClassB
#dynamic value;
...
#end
I think it should work for you.