please help me, i'm very new in objective-c
i've got 2 simplest classes (bellow first, second)
i would like to set the offsetx properties of self.rolypoly object in second class like a self.rolypoly.offsetx=1 or run use [self.rolypoly setOffx]; to do somethings, but i always have the errors:
trying [self.rolypoly setOffx]; in second class
-[CCScene setOffx:]: unrecognized selector sent to instance 0x91d0b70' 
or
trying self.rolypoly.offsetx=1;  in second class
-[CCScene setOffsetx:]: unrecognized selector sent to instance 0x808bfc0'
first class
//************************************************************ 
       #import <Foundation/Foundation.h>
        #import "cocos2d.h"
        @interface RolyPoly : CCLayer {
            CCAction *_walkAction; 
            CCSprite *_rolypoly;
            int offsetx;
            int offsety;
        }
        @property (nonatomic, retain) CCSprite *rolypoly;
        @property (nonatomic, retain) CCAction *walkAction;
        @property (nonatomic, assign) int offsetx;
        @property (nonatomic, assign) int offsety;
        +(id) scene;
        -(void) setOffx;
        @end
//************************************************************     
        #import "GameLayer.h"
        #import "RolyPoly.h"
        @implementation RolyPoly
        @synthesize rolypoly = _rolypoly;
        @synthesize walkAction = _walkAction;
        @synthesize  offsetx = _offsetx;
        @synthesize  offsety = _offsety;
        +(id) scene
        {
            CCScene *scene = [CCScene node];
            RolyPoly *layer = [RolyPoly node];
            [scene addChild: layer];
            return scene;
        }
        -(id) init
        {
            if ((self = [super init]))
            {
                [self scheduleUpdate];
            }
            return self;
        }
        -(void) setOffx
        {
            NSLog(@"setOffx");
        }
        -(void) update:(ccTime)delta
        {
        }
        - (void) dealloc
        {
            self.rolypoly = nil;
            self.walkAction = nil;
            [super dealloc];
        }
        @end
second class
//************************************************************ 
    #import <Foundation/Foundation.h>
    #import "cocos2d.h"
    #import "RolyPoly.h"
    @interface GameLayer : CCLayer {
        RolyPoly *_rolypoly;
    }
    // returns a CCScene that contains the HelloWorldLayer as the only child
    +(CCScene *) scene;
    @property (nonatomic, assign) RolyPoly * rolypoly;
    @end
//************************************************************   
    #import "GameLayer.h"
    #import "RolyPoly.h"
    // HelloWorldLayer implementation
    @implementation GameLayer
    @synthesize  rolypoly = _rolypoly;
    +(CCScene *) scene
    {
        CCScene *scene = [CCScene node];
        GameLayer *layer = [GameLayer node];
        [scene addChild: layer];
        return scene;
    }
    -(id) init
    {
        if( (self=[super init])) {
            CGSize screenSize = [[CCDirector sharedDirector] winSize];
            self.rolypoly = [RolyPoly scene];
            [self addChild:self.rolypoly z:1];
            [self.rolypoly setOffx];
            [self scheduleUpdate];
        }
        return self;
    }
    - (void)update:(ccTime)dt {
    }
    - (void) dealloc
    {
        [super dealloc];
    }
    @end