ios - NSCoder 没有正确返回值

Question

在下面的代码中，sharedInstance 方法中的属性从未正确设置，我不明白为什么。在我用存档器保存它之前，我似乎有正确的值。

  #import "User.h"

  static User *sharedInstance = nil;

  #define NAME @"name"
  #define USER_ID @"id"
  #define ACCOUNT_ID @"account_id"
  #define USER_NAME @"username"
  #define ADMIN @"admin"
  #define CURRENT_USER @"current_user"

  @implementation KSUser

  + (id)sharedInstance
  {
      @synchronized(self) {
          if (sharedInstance == nil) {
              NSData *userData = [[NSUserDefaults standardUserDefaults] objectForKey:CURRENT_USER];
              if (userData) {
                  sharedInstance = [NSKeyedUnarchiver unarchiveObjectWithData:userData];
              }
              else {
                  sharedInstance = [[super alloc] init];
              }
          }
      }
      return sharedInstance;
  }

  - (void)populateFromJSON:(NSDictionary *)json
  {
      sharedInstance.name = json[NAME];
      sharedInstance.accountId = json[ACCOUNT_ID];
      sharedInstance.userId = json[USER_ID];
      sharedInstance.userName = json[USER_NAME];
      sharedInstance.admin = [json[ADMIN] boolValue];
      sharedInstance.loggedIn = YES;
      NSLog(@"values are: name: %@, %@, %@, %@", sharedInstance.name, sharedInstance.accountId, sharedInstance.userId, sharedInstance.userName);
  }

  - (void)logout
  {
      sharedInstance.name = nil;
      sharedInstance.accountId = nil;
      sharedInstance.userId = nil;
      sharedInstance.userName = nil;
      sharedInstance.admin = NO;
      sharedInstance.loggedIn = NO;
      [self saveState];

  }

  - (void)saveState
  {
      NSLog(@"values are: name: %@, %@, %@, %@", sharedInstance.name, sharedInstance.accountId, sharedInstance.userId, sharedInstance.userName);
      NSData *data = [NSKeyedArchiver archivedDataWithRootObject:sharedInstance];
      [[NSUserDefaults standardUserDefaults] setObject:data forKey:CURRENT_USER];
  }

  - (void)encodeWithCoder:(NSCoder *)aCoder
  {
      [aCoder encodeObject:sharedInstance.userId forKey:USER_ID];
      [aCoder encodeObject:sharedInstance.accountId forKey:ACCOUNT_ID];
      [aCoder encodeObject:sharedInstance.name forKey:NAME];
      [aCoder encodeObject:sharedInstance.userName forKey:USER_NAME];
      [aCoder encodeBool:sharedInstance.admin forKey:ADMIN];
  }

  - (id)initWithCoder:(NSCoder *)aDecoder
  {
      if (self = [super init]) {
          sharedInstance.userId = [aDecoder decodeObjectForKey:USER_ID];
          sharedInstance.accountId = [aDecoder decodeObjectForKey:ACCOUNT_ID];
          sharedInstance.name = [aDecoder decodeObjectForKey:NAME];
          sharedInstance.userName = [aDecoder decodeObjectForKey:USER_NAME];
          sharedInstance.admin = [aDecoder decodeBoolForKey:ADMIN];
      }
      return self;
  }

  @end

如有任何帮助，我们将不胜感激。

Answer 1

这是因为你的全局变量 sharedinstance 在方法 - (id)initWithCoder:(NSCoder *)aDecoder 中总是 nil