iOS Accessing Value of a property of a derived class

[wisaunders]

I'm having trouble getting the value of a property of my class. My class is called ball and I'd like to get it's velocity (which i set but can change) from my view control.

Here is my ball.h code:

#import <Foundation/Foundation.h>

@interface Ball : UIImageView {
	CGPoint ballVelocity;
    int mXSpeed;
    int mYSpeed;
    float mAngle;
}


- (void)getVelocity:(CGPoint)speed;
- (void)move;
- (void)bounceHorizontal;
- (void)bounceVertical;
- (void)setSpeedX:(int)xSpeed Y:(int)ySpeed;
- (void)setVelocity:(CGPoint)speed;
- (CGPoint) ballVelocity;

@end

Here is my part of my ball.m code:

#import "Ball.h"


@implementation Ball


- (void)setVelocity:(CGPoint)speed {
    ballVelocity = speed;
}

Here is my viewVontroller.h

#import <UIKit/UIKit.h>


@class Ball;

@interface BallsOfFireViewController : UIViewController {
	IBOutlet UIImageView *ball;
	NSMutableArray *mBallArray;
	CGPoint   ballVelocity;	
	CGPoint   velocityz;
	CGPoint   velocityz2;
}

@property(nonatomic, retain) IBOutlet UIImageView *ball;
@property(retain, nonatomic) IBOutlet NSMutableArray *mBallArray;
@property(nonatomic) CGPoint ballVelocity;

- (void) checkCollision;
@end

and here is the relative code from my viewController.m

#import "BallsOfFireViewController.h"
#import "Ball.h"

//#define kGameStateRunning 1
//#define kGameStatePaused  2

#define kBallSpeedX 1
#define kBallSpeedY 1

@implementation BallsOfFireViewController
@synthesize ball, mBallArray, ballVelocity;



- (void)viewDidLoad {
    [super viewDidLoad];
	//self.gameState = kGameStatePaused;

	
	mBallArray = [[NSMutableArray alloc] init];
	int i;
	for (i = 0; i < 3; i++)
	{
		Ball* ballx=[[Ball alloc] initWithImage:[UIImage imageNamed:@"FireBall.png"]];
		[mBallArray addObject:ballx];
		[self.view addSubview:ballx];
		
		if (i == 14
			){
			//[ballx setBackgroundColor:([UIColor redColor])];	
			ballx.image = [UIImage imageNamed:@"IceBall.png"];
		}
		
		ballVelocity = CGPointMake(1,1);
		[ballx setVelocity:ballVelocity];
		
		ballx.center = CGPointMake((random() % 14) * 20 + 20 ,(random() % 20) * 20 + 20);		

	}
	
		
	[NSTimer scheduledTimerWithTimeInterval:0.005
									 target:self 
								   selector:@selector(moveBall) 
								   userInfo:nil 
									repeats:YES];       	
	
}




-(void)moveBall
{
	int i;
	int numberOfBalls=[mBallArray count];
	for (i = 0; i < numberOfBalls; i++)
	{
		
		Ball* ballz=[mBallArray objectAtIndex:i]; 
		
		int i2;
		for (i2 = 0; i2 < numberOfBalls; i2++)
			if (i2 != i) {
				Ball* ballz2=[mBallArray objectAtIndex:i2]; 
				
				if (CGRectIntersectsRect(ballz.frame, ballz2.frame)) {
					
					if (sqrt(pow(ballz.center.x - ballz2.center.x,2) + pow(ballz.center.y - ballz2.center.y,2)) <= pow(ballz.frame.size.width,2)) {
	
						
						[ballz move];
						 velocityz  = ballz.ballVelocity;
						 velocityz2 = ballz2.ballVelocity;
						
						if (velocityz.x == velocityz2.x * -1 && velocityz.y == velocityz2.y * -1) {
							
							if (pow(ballz.center.x - ballz2.center.x,2) > pow(ballz.center.y - ballz2.center.y,2)) {
								
								[ballz bounceHorizontal];
								[ballz2 bounceHorizontal];	
							} else {
								[ballz bounceVertical];
								[ballz2 bounceVertical];	
							}
							
						}						
						
					}
					
					
				}

			} 

		[ballz move];
	}

	
}

When I get to the following line in debug mode the game in my iPhone Simulator freezes and I do not see any errors in xCode (probably don't know where to look):

velocityz  = ballz.ballVelocity;

I think I'm just not setting up my ball class correctly to be able to pull back the value of the ballVelocity variable. Can anyone point me in the correct direction?

 

[kainjow]

I don't see a direct problem from a quick glance, but when it freezes go to Run > Debugger and see what it's showing.

Also you should be consistent with your use of properties and accessor methods. You use ballz.ballVelocity but ballVelocity is not defined as a @property, so it should be [ballz ballVelocity] - same goes for all the other attributes of your Ball class.

Additionally, when you call [[Ball alloc] initWithImage...], you should add an autorelease to that, otherwise you're leaking:

Ball* ballx=[[[Ball alloc] initWithImage:[UIImage imageNamed:@"FireBall.png"]] autorelease];

 

[plinden]

To add to what kainjow has mentioned, I don't see where you're trying to get velocity from a ball, but the following line stands out to me:

- (void)getVelocity: (CGPoint)speed;

Not only that you're passing in a value to a getter, but in Obj-C you don't access a property using getX ... this isn't a JavaBean - use:
- (CGPoint)velocity;

 

[wisaunders]

asm___TERMINATING_DUE_TO_UNCAUGHT_EXCEPTION__ 0x01c1c0001:1

Thanks

here's what i see in the dubugger when it stops:

[NSObject doesNotRecognizeSelector:]

this is the line of code it is trying to execute:

velocityz = ballz.ballVelocity

Still don't know what to do

 

[Guiyon]

If I am reading the code correctly, ballz is defined as:

Ball* ballz2=[mBallArray objectAtIndex:i];

Looking at your interface for the Ball class, there is no ballVelocity property defined so using

ballz2.ballVelocity

is incorrect and should be

[ballz ballVelocity]

In order for it to work as a property you would need to add a property definition to the Ball class (like in BallsOfFireViewController) and create the property using either @synthesize or @dynamic. Additionally, your methods for the property (assuming you dynamically assign them) would need to be fixed as, by default, the compiler would be looking for methods

- (CGPoint)ballVelocity;
- (void)setBallVelocity:(CGPoint);

as your accessor and mutator methods (your accessor has the right signature but your mutator needs to be changed).