在dealloc中保存对象状态无效

NSString

+(void)savePreferences:(NSString*)key :(NSString*)value{
    NSMutableString* mutableString=[[NSMutableString alloc]initWithString:value];
    CFPreferencesSetAppValue((CFStringRef)key, mutableString, kCFPreferencesCurrentApplication);    // Set up the preference.
    CFPreferencesAppSynchronize(kCFPreferencesCurrentApplication);// Write out the preference data.
    [mutableString release];
}