使用NSKeyedUnarchiver出错

Question

我正在编写一个iPhone应用程序，并且在试图归档设置时遇到了问题。我使用一个类( AppData )来保存设置(示例目前只显示一个)，并在应用程序加载时使用AppData创建AppData实例，并在应用程序结束时存储它。我遵守(我认为) NSCoding协议。

应用程序将文件存储在Documents目录OK中，检查文件结构似乎保存了我期望的数据。但是，当文件加载到未存档程序中时，返回错误。

***终止应用程序，原因是“NSInvalidUnarchiveOperationException”异常，原因：*** -NSKeyedUnarchiver decodeObjectForKey:：unarchiver已完成；无法再解码任何内容

我和这个问题斗争了一段时间了，所以如果有人能看到这个问题，我会非常感激的。

代码：

应用程序代表：

接口：

#import <UIKit/UIKit.h>
#import "AppData.h"
#import "Constants.h"

@interface iLeanAppDelegate : NSObject <UIApplicationDelegate> {
    AppData *appData;
    UIWindow *window;
    UITabBarController *tabBarController;
}

@property (nonatomic, retain) IBOutlet UIWindow *window;
@property (nonatomic, retain) IBOutlet UITabBarController *tabBarController;
@property (nonatomic, retain) AppData *appData;

@end

执行情况：

#import "iLeanAppDelegate.h"


@implementation iLeanAppDelegate

@synthesize window;
@synthesize tabBarController; 
@synthesize appData;

- (void)applicationDidFinishLaunching:(UIApplication *)application {

    appData = [[AppData alloc] init];
    if ([[NSFileManager defaultManager] fileExistsAtPath:[AppData dataFilePath]]) {         //If previous settings have been found retrieve and initialise
        NSData *data = [[NSMutableData alloc] initWithContentsOfFile:[AppData dataFilePath]];
        NSKeyedUnarchiver *unarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:data];
        [unarchiver finishDecoding];    
    appData = [unarchiver decodeObjectForKey:kDataKey];
        [unarchiver finishDecoding];

    [unarchiver release];
    [data release];
}

// Add the tab bar controller's current view as a subview of the window
[window addSubview:tabBarController.view];
}

-(void)applicationWillTerminate:(NSNotification *)notification {
    NSMutableData *data = [[NSMutableData alloc] init];
    NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:data];
    [archiver encodeObject:appData forKey:kDataKey];
    [archiver finishEncoding];
    BOOL success = [data writeToFile:[AppData dataFilePath] atomically:YES];
    if (success)
        NSLog(@"OK");
    else
        NSLog(@"Problem here");
    [archiver release];
    [data release];

}

- (void)dealloc {
    [tabBarController release];
    [window release];
[appData release];
    [super dealloc];
}

@end

AppData类：

接口：

#import <Foundation/Foundation.h>
#import "Constants.h"

@interface AppData : NSObject <NSCoding, NSCopying> {

    BOOL audioAlert;        //YES = audio alerts are on, NO = audio alerts are off
}

+(NSString *)dataFilePath;

@property(nonatomic, assign) BOOL audioAlert;

@end

执行情况：

#import "AppData.h"


@implementation AppData

@synthesize audioAlert;


+(NSString *)dataFilePath {
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    return [documentsDirectory stringByAppendingPathComponent:kSettingsFilename];
}


#pragma mark NSCoding

-(void)encodeWithCoder:(NSCoder *)encoder {

    [encoder encodeBool:audioAlert forKey:kSettingsKey];
}

-(id)initWithCoder:(NSCoder *)decoder {
    if (self = [super init]) {
        self.audioAlert = [decoder decodeObjectForKey:kSettingsKey];
    }

    return self;
}

#pragma mark -
#pragma mark NSCopying

-(id)copyWithZone:(NSZone *)zone {
    AppData *copy = [[[self class] allocWithZone: zone] init];
//Will do this once coding works
    return copy;
}

@end

终于定式了。

//此文件包含所有应用程序常量

#define kSettingsFilename   @"archive"  //Filename where all application settings are stored

#define kSettingsKey        @"settingsKey"      //Key name
#define kDataKey            @"data"

Answer 1

正如错误消息声明的那样，您正在完成解码之前调用finishDecoding。然后你又叫它：

[unarchiver finishDecoding];    
appData = [unarchiver decodeObjectForKey:kDataKey];
[unarchiver finishDecoding];

那是行不通的。

也就是说，您的代码比需要的要复杂得多。为什么不这样做：

// Encoding:
NSData *data = [NSKeyedArchiver archivedDataWithRootObject:appData];

// Decoding:
appData = [NSKeyedUnarchiver unarchiveObjectWithData:data];