NSKeyedUnarchiver 对象被破坏？

Question

我有一个保存到 NSUserDefaults 的数组，其中包含我的自定义类分配的数组，它符合 NSCoding 协议。数组正确保存和加载，我可以验证检索到的数组的第一个对象是否属于Assignment 类。当我尝试访问数组中赋值对象的 ivars 时，就会出现问题。它崩溃了，我收到以下错误：

*** -[CFString respondsToSelector:]: message sent to deallocated instance 0x3948d60

这是我用来保存到用户默认值的代码。请注意，我还检索并检查保存的对象以进行调试。

 -(void)saveToUserDefaults:(NSArray*)myArray
{
    NSUserDefaults *standardUserDefaults = [NSUserDefaults standardUserDefaults];

    if (standardUserDefaults) {
        [standardUserDefaults setObject:[NSKeyedArchiver archivedDataWithRootObject:myArray] forKey:@"Assignments"];
        [standardUserDefaults synchronize];
    }
    NSLog(@"Assignments array saved. (%d assignments in array)",[myArray count]);
    NSData *dataCheck = [[NSData alloc] initWithData:[standardUserDefaults objectForKey:@"Assignments"]];
    NSArray *arrayCheck = [[NSArray alloc] initWithArray:[NSKeyedUnarchiver unarchiveObjectWithData:dataCheck]];
    NSLog(@"Checking saved array (%d assignments in array)",[arrayCheck count]);
    if ([[arrayCheck objectAtIndex:0] isKindOfClass:[Assignment class]]) {
        NSLog(@"It's of the class Assignment.");
    }
    Assignment *testAssignment = [[Assignment alloc] initWithAssignment:[arrayCheck objectAtIndex:0]];
    NSLog(@"Title: %@ Course: %@",[testAssignment title],[testAssignment course]);
}

一切都很好，直到我分配 testAssignment，这就是崩溃发生的地方。有人有什么想法吗？

编辑：这是我在Assignment类中的NSCoding方法：

- (void)encodeWithCoder:(NSCoder *)coder {
    [coder encodeObject:title forKey:@"title"];
    [coder encodeObject:course forKey:@"course"];
    [coder encodeObject:dueDate forKey:@"dueDate"];
    [coder encodeObject:notes forKey:@"notes"];
}

- (id)initWithCoder:(NSCoder *)coder {
    self = [[Assignment alloc] init];
    if (self != nil)
    {
        title = [coder decodeObjectForKey:@"title"];
        course = [coder decodeObjectForKey:@"course"];
        dueDate = [coder decodeObjectForKey:@"dueDate"];
        notes = [coder decodeObjectForKey:@"notes"];
    }   
    return self;
}

Answer 1

回答了我自己的问题。在 initWithCoder 中，我需要保留我正在解码的所有对象：

//Example    
title = [[coder decodeObjectForKey:@"title"] retain];

现在一切都工作得很好。 :)