游戏状态单例 cocos2d，initWithEncoder 总是返回 null

Posted 2023-02-27

【中文标题】游戏状态单例 cocos2d，initWithEncoder 总是返回 null

【英文标题】：game state singleton cocos2d, initWithEncoder always returns null

【发布时间】：2010-04-19 20:56:12

【问题描述】：

我正在尝试在 cocos2d 中编写一个基本的测试“游戏状态”单例，但由于某种原因，在加载应用程序时，从未调用过 initWithCoder。任何帮助将不胜感激，谢谢。

这是我的单例 GameState.h：

#import "cocos2d.h"

@interface GameState : NSObject <NSCoding>

  NSInteger level, score;
  Boolean seenInstructions;


@property (readwrite) NSInteger level;
@property (readwrite) NSInteger score;
@property (readwrite) Boolean seenInstructions;

+(GameState *) sharedState;
+(void) loadState;
+(void) saveState;

@end

... 和 GameState.m：

#import "GameState.h"
#import "Constants.h"

@implementation GameState

static GameState *sharedState = nil;

@synthesize level, score, seenInstructions;

-(void)dealloc 
  [super dealloc];


-(id)init 
  if(!(self = [super init]))
    return nil;  
  level = 1;
  score = 0;
  seenInstructions = NO;

  return self;


+(void)loadState 
  @synchronized([GameState class])     
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    NSString *saveFile = [documentsDirectory stringByAppendingPathComponent:kSaveFileName];
    Boolean saveFileExists = [[NSFileManager defaultManager] fileExistsAtPath:saveFile];

    if(!sharedState) 
      sharedState = [GameState sharedState];
    

    if(saveFileExists == YES) 
      [sharedState release];
      sharedState = [[NSKeyedUnarchiver unarchiveObjectWithFile:saveFile] retain];
    
    // at this point, sharedState is null, saveFileExists is 1
    if(sharedState == nil) 
      // this always occurs
      CCLOG(@"Couldn't load game state, so initialized with defaults");
      sharedState = [self sharedState];
    
    


+(void)saveState 
  NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
  NSString *documentsDirectory = [paths objectAtIndex:0];
  NSString *saveFile = [documentsDirectory stringByAppendingPathComponent:kSaveFileName];
  [NSKeyedArchiver archiveRootObject:[GameState sharedState] toFile:saveFile];


+(GameState *)sharedState 
  @synchronized([GameState class]) 
    if(!sharedState) 
      [[GameState alloc] init];
    
    return sharedState;
  
  return nil;


+(id)alloc 
  @synchronized([GameState class]) 
    NSAssert(sharedState == nil, @"Attempted to allocate a second instance of a singleton.");
    sharedState = [super alloc];
    return sharedState;
  
  return nil;


+(id)allocWithZone:(NSZone *)zone

  @synchronized([GameState class]) 
    if(!sharedState) 
      sharedState = [super allocWithZone:zone];
      return sharedState;
    
   
  return nil;


...

-(void)encodeWithCoder:(NSCoder *)coder 
  [coder encodeInt:level forKey:@"level"];
  [coder encodeInt:score forKey:@"score"];
  [coder encodeBool:seenInstructions forKey:@"seenInstructions"];


-(id)initWithCoder:(NSCoder *)coder 
  CCLOG(@"initWithCoder called");
  self = [super init];
  if(self != nil) 
    CCLOG(@"initWithCoder self exists");
    level = [coder decodeIntForKey:@"level"];
    score = [coder decodeIntForKey:@"score"];
    seenInstructions = [coder decodeBoolForKey:@"seenInstructions"];
  
  return self;

@end

...我正在保存应用退出时的状态，如下所示：

- (void)applicationWillTerminate:(UIApplication *)application 
  [GameState saveState];
  [[CCDirector sharedDirector] end];

...并在应用完成加载时加载状态，如下所示：

- (BOOL) application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions

  ...
  [GameState loadState];
  ...

我也尝试过在我调用 loadState 的地方移动，例如在我的主 CCScene 中，但这似乎也不起作用。

再次提前致谢。

【参考方案1】：

正义！我想我想通了。另外，我发现了一个不错的启动宏：http://cocoawithlove.com/2008/11/singletons-appdelegates-and-top-level.html

我正在使用修改后的宏：http://github.com/taberrr/Objective-C-Optimized-Singleton.git（我喜欢“sharedGameState”而不是“sharedInstance”）

希望这会帮助其他人尝试做同样的事情......这是我工作的 NSCoder GameState 单例：

GameState.h：

#import "SynthesizeSingleton.h"
#import "cocos2d.h"

@interface GameState : NSObject <NSCoding>

  NSInteger level, score;
  Boolean seenInstructions;


@property (readwrite) NSInteger level;
@property (readwrite) NSInteger score;
@property (readwrite) Boolean seenInstructions;

SYNTHESIZE_SINGLETON_FOR_CLASS_HEADER(GameState);

+(void)loadState;
+(void)saveState;

@end

GameState.m：

#import "SynthesizeSingleton.h"
#import "GameState.h"
#import "Constants.h"

@implementation GameState

@synthesize level, score, seenInstructions;

SYNTHESIZE_SINGLETON_FOR_CLASS(GameState);

- (id)init 
  if((self = [super init])) 

    self.level = 1;
    self.score = 0;
    self.seenInstructions = NO;

  
  return self;


+(void)loadState

  @synchronized([GameState class]) 
    // just in case loadState is called before GameState inits
    if(!sharedGameState)
      [GameState sharedGameState];

    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    NSString *file = [documentsDirectory stringByAppendingPathComponent:kSaveFileName];
    Boolean saveFileExists = [[NSFileManager defaultManager] fileExistsAtPath:file];

    if(saveFileExists) 
      // don't need to set the result to anything here since we're just getting initwithCoder to be called.
      // if you try to overwrite sharedGameState here, an assert will be thrown.
      [NSKeyedUnarchiver unarchiveObjectWithFile:file];
    
  


+(void)saveState

  @synchronized([GameState class])   
    GameState *state = [GameState sharedGameState];

    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    NSString *saveFile = [documentsDirectory stringByAppendingPathComponent:kSaveFileName];

    [NSKeyedArchiver archiveRootObject:state toFile:saveFile];
  


#pragma mark -
#pragma mark NSCoding Protocol Methods

-(void)encodeWithCoder:(NSCoder *)coder

  [coder encodeInt:self.level forKey:@"level"];
  [coder encodeInt:self.score forKey:@"score"];
  [coder encodeBool:self.seenInstructions forKey:@"seenInstructions"];


-(id)initWithCoder:(NSCoder *)coder

  self = [super init];
  if(self != nil) 
    self.level = [coder decodeIntForKey:@"level"];
    self.score = [coder decodeIntForKey:@"score"];
    self.seenInstructions = [coder decodeBoolForKey:@"seenInstructions"];
  
  return self;


@end

保存：

- (void)applicationWillTerminate:(UIApplication *)application 
  ...
  [GameState saveState];
  ...

加载中：

// somewhere in your app, maybe in applicationDidFinishLaunching
GameState *state = [GameState sharedGameState];
NSLog(@"sharedGameState: %@", state);
[GameState loadState];

如果有人对此有任何疑问，请说出来。 :)

不过，它似乎工作正常。

【参考方案2】：

您无需下载修改后的宏。原来的 allocWithZone 返回 nil。只需像这样更正原始的：

来自：

+ (id)allocWithZone:(NSZone *)zone \
 \
    @synchronized(self) \
     \
        if (shared##classname == nil) \
         \
            shared##classname = [super allocWithZone:zone]; \
            return shared##classname; \
         \
     \
    \
    return nil; \
 \

到：

+ (id)allocWithZone:(NSZone *)zone \
 \
    @synchronized(self) \
     \
        if (shared##classname == nil) \
         \
            shared##classname = [super allocWithZone:zone]; \
         \
     \
    \
    return shared##classname; \
 \