objective-c - CCCallFunc 和 ARC

Question

这是我的问题 我试图在 cocos2d for iphone 中为 Action 序列创建一个回调函数，但我一直收到错误的访问错误。

我在这里创建我的回调

id myCallFunc = [CCCallFuncND actionWithTarget:self.delegate selector:@selector(playerAttack:data:) data:(__bridge void *)([[PlayerAttackPacket alloc] initWithPlayer:@"" attackChoice: [NSNumber numberWithInt: item.tag]]) ]; // to call our method

这是被回调的函数，当转换数据时，编译器说访问错误。

-(void) playerAttack:(id)sender data:(void *)data
{
    PlayerAttackPacket* packet = (__bridge PlayerAttackPacket*)data;
    BattleModel *model = [BattleModel sharedInstance];
    int choice = packet.attackChoice.intValue;
    NSString * players = packet.player;
}

播放器数据包:

@interface PlayerAttackPacket : NSObject {
    NSString * player;
    NSNumber * attackChoice;
}

@property (nonatomic, retain) NSString * player;
@property (nonatomic, retain) NSNumber * attackChoice;
-(id) initWithPlayer: (NSString*)_player attackChoice: (NSNumber*)choice;
@end

@implementation PlayerAttackPacket
@synthesize player,attackChoice;

-(id) initWithPlayer: (NSString*)_player attackChoice: (NSNumber*)choice
{
    if((self=[super init]))
    {
        self.player = _player;
        self.attackChoice = choice;
    }
    return self;
}
@end

谁能告诉我我做错了什么？ =(。我的感觉是它与 ARC 有关，但我不确定。

Answer 1

为了可读性，这里是你的 call func 方法重新格式化:

void* data = (__bridge void*)[[PlayerAttackPacket alloc] initWithPlayer:@"" 
                               attackChoice: [NSNumber numberWithInt: item.tag]];
id myCallFunc = [CCCallFuncND actionWithTarget:self.delegate 
           selector:@selector(playerAttack:data:) data:data ];

你做的是这样的:

• 分配新对象
• bridge 将其转换为 void*
• 将其传递给 CCCallFuncND

ARC 看到/做的是这样的:

• 分配新对象
• 新对象桥投(忽略)
• 对象在调用 func 后超出范围
• 释放对象

您没有保留对该对象的强引用，因此它会在执行选择器时释放。请不要使用 Ben 的建议，我知道它有效，但它也很危险，因为只要 call func 操作实际上没有执行选择器，它就会泄漏内存，即停止操作/序列或调用时更改场景func 仍在运行，等待执行选择器。

您可以通过两种方式解决此问题:

• 保持对新对象的强引用直到选择器被执行，即作为类的实例变量
• 改为使用 CCCallBlock

一定要使用方 block !它避免了内存管理问题，您也不必对该对象有强引用。事实上，您甚至不必将其传递给 block !这是它的工作原理:

PlayerAttackPacket* packet = [[PlayerAttackPacket alloc] initWithPlayer:@"" 
                               attackChoice: [NSNumber numberWithInt: item.tag]];

id myCallBlock = [CCCallBlock actionWithBlock:^{

    // no bridge casting required, packet variable is accessible within the block
    // no memory management needed, block copies packet and keeps it alive
    BattleModel *model = [BattleModel sharedInstance];
    int choice = packet.attackChoice.intValue;
    NSString * players = packet.player;
           }];

现在我有点猜测，但在我看来，您创建 PlayerAttackPacket 类只是为了将几个参数传递到 CCCallFuncND。您也可以使用 block 跳过它!

NSString* player = @"player1";

id myCallBlock = [CCCallBlock actionWithBlock:^{

    // whatever variables you need from the surrounding scope, you can just use
    // them as if they were local variables in the block!
    int choice = item.tag;
    NSString * players = player;
           }];

block 非常方便，并且可以更好地与 ARC 配合使用。使用积木!重复:use blocks .