EXC_BAD_ACCESS when adding joint to physicsworld

Question

I dont understand what I am doing wronge - trying to add SKPhysicsJointFixed between 2 SKSpriteNodes - but when add them to self.physicsWorld
i get  a EXC BAD ACCES...
going mad over this problem... where am i going awry? thanks for your help
-(void) createTheSlope:(CGPoint)location{
    SKSpriteNode    *slope=[[SKSpriteNode alloc]initWithColor:[SKColor brownColor] size:CGSizeMake(100, 20)];
    slope.physicsBody=[SKPhysicsBody bodyWithRectangleOfSize:slope.size];
    SKSpriteNode  *nob=[[SKSpriteNode alloc]initWithColor:[SKColor purpleColor] size:CGSizeMake(20, 20)];
    nob.physicsBody=[SKPhysicsBody bodyWithRectangleOfSize:nob.size];
    nob.position=location;
    //SKAction *merot=[SKAction rotateByAngle:360 duration:55];
   // slope.position=CGPointMake(CGRectGetMidX(self.frame), CGRectGetMidY(self.frame));
    slope.position=location;
    slope.physicsBody.dynamic=NO;
    nob.physicsBody.dynamic=NO;
    SKPhysicsJointFixed *lock=[SKPhysicsJointFixed jointWithBodyA:slope.physicsBody     bodyB:nob anchor:location];
    [self.physicsWorld addJoint:lock];
    //[slope runAction:merot];
    [self addChild:slope];
    [self addChild:nob];

Answer 1

Both jointWithBodyA: and bodyB: seem to expect the same argument, an SkPhysicsBody * but your argument to bodyB: nob seems to be an SkSpriteNode.
Shouldn't the argument for bodyB: be nob.physicsBody ?