在COCOS2D v3中子类化CCSprite

Question

Hi I recently updated to COCOS2D v3 and the code I used to use to subclass a CCSprite no longer works and I am getting an error when I try to assign values to my properties.

@interface Alien : CCSprite
{

int _minMoveDuration;
int _maxMoveDuration;
int _hp;
}

@property (nonatomic, assign) int hp;
@property (nonatomic, assign) int minMoveDuration;
@property (nonatomic, assign) int maxMoveDuration;

@end

@interface SmallFastAlien: Alien
{

}
+(id)alien;
@end 

Inside the main file I then set my properties for the alien class:

#import "Alien.h"

@implementation Alien

@synthesize hp = _hp;
@synthesize minMoveDuration = _minMoveDuration;
@synthesize maxMoveDuration = _maxMoveDuration;

@end

@implementation SmallFastAlien

+ (id)alien
{
SmallFastAlien *alien = nil;
/*if ((alien = [[[super alloc] initWithSpriteFrameName:@"small-1.png"] autorelease]))
{

}*/
alien = [CCSprite spriteWithImageNamed:@"small-1.png"];

alien.hp = 1;
//alien.minMoveDuration = 3;
//alien.maxMoveDuration = 5;

return alien;
}

@end

However, I then get an error when the hp property is set. This did work in v2, but no longer works in v3 and gives the following error:

-[CCSprite setHp:]: unrecognized selector sent to instance 0x10a4c5cb0

Any advice would be greatly appreciated.

Answer 1

You create a CCSprite, that's why:

alien = [CCSprite spriteWithImageNamed:@"small-1.png"];

You ought to be creating an instance of your class, for instance:

alien = [SmallFastAlien spriteWithImageNamed:@"small-1.png"];

PS: ivar declaration in @interface and @synthesize in @implementation are unnecessary, so is the assign keyword (specifically for int and other primitive data types). Xcode auto-synthesizes ivars (with underscore prefix) and getter/setter, assign only affects object ( id ) types. You can shorten your code to:

@interface Alien : CCSprite

@property (nonatomic) int hp;
@property (nonatomic) int minMoveDuration;
@property (nonatomic) int maxMoveDuration;

@end


@implementation Alien

@end