RestKit 0.9.3 连接关系：withObjectForPrimaryKeyAttribute：

Posted 2023-03-05

【中文标题】RestKit 0.9.3 连接关系：withObjectForPrimaryKeyAttribute：

【英文标题】：RestKit 0.9.3 connectRelationship:withObjectForPrimaryKeyAttribute:

【发布时间】：2011-09-07 08:46:49

【问题描述】：

我正在尝试使用来自新 RestKit 0.9.3 的示例 RKCatalog。 在 RKRelationshipMappingExample 中，创建者忘记在 Task 和 User 之间添加连接代码，但即使添加后也无法正常工作。

"project": 
    "id": 123,
    "name": "Produce RestKit Sample Code",
    "description": "We need more sample code!",
    "user": 
        "id": 1,
        "name": "Blake Watters",
        "email": "[e-mail]"
    ,
    "tasks": [
        "id": 1, "name": "Identify samples to write", "assigned_user_id": 1,
        "id": 2, "name": "Write the code", "assigned_user_id": 1,
        "id": 3, "name": "Push to Github", "assigned_user_id": 1,
        "id": 4, "name": "Update the mailing list", "assigned_user_id": 1
    ]

---

[taskMapping connectRelationship:@"assignedUser" withObjectForPrimaryKeyAttribute:@"assignedUserID"];

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil 
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) 
        RKObjectManager* objectManager = [RKObjectManager objectManagerWithBaseURL:gRKCatalogBaseURL];
        objectManager.objectStore = [RKManagedObjectStore objectStoreWithStoreFilename:@"RKRelationshipMappingExample.sqlite"];

        RKManagedObjectMapping* taskMapping = [RKManagedObjectMapping mappingForClass:[Task class]];
        [taskMapping mapKeyPath:@"id" toAttribute:@"taskID"];
        [taskMapping setPrimaryKeyAttribute:@"taskID"];
        [taskMapping mapKeyPath:@"name" toAttribute:@"name"];
        [taskMapping mapKeyPath:@"assigned_user_id" toAttribute:@"assignedUserID"];
        [taskMapping connectRelationship:@"assignedUser" withObjectForPrimaryKeyAttribute:@"assignedUserID"];
        [objectManager.mappingProvider setMapping:taskMapping forKeyPath:@"task"];

        RKManagedObjectMapping* userMapping = [RKManagedObjectMapping mappingForClass:[User class]];
        [userMapping mapAttributes:@"name", @"email", nil];
        [userMapping mapKeyPath:@"id" toAttribute:@"userID"];
        [userMapping setPrimaryKeyAttribute:@"userID"];
        [userMapping mapRelationship:@"tasks" withMapping:taskMapping];
        [objectManager.mappingProvider setMapping:userMapping forKeyPath:@"user"];

        // NOTE - Project is not backed by Core Data
        RKObjectMapping* projectMapping = [RKObjectMapping mappingForClass:[Project class]];
        [projectMapping mapKeyPath:@"id" toAttribute:@"projectID"];
        [projectMapping mapAttributes:@"name", @"description", nil];
        [projectMapping mapRelationship:@"user" withMapping:userMapping];
        [projectMapping mapRelationship:@"tasks" withMapping:taskMapping];
        [objectManager.mappingProvider setMapping:projectMapping forKeyPath:@"project"];
    

    return self;

我做的一切都好吗？ -- 它不会通过用户 ID 将任务连接到用户。

【参考方案1】：

更新：我应该更仔细地阅读Blake's linked post——它会更快地将我指向开发分支。

底线：一对多映射问题（在 User 对象的 tasks 的反向水合的上下文中讨论）在 0.9.3 中被破坏。截至 2012 年 3 月 8 日，开发分支的拉动确认该问题已在此处解决——布莱克在问题 #284 中解决了该问题。您确实仍然需要添加示例不包含的connectRelationship:withObjectForPrimaryKeyAttribute: 逻辑。

---

@Evan，感谢RKLogConfigureByName("RestKit/ObjectMapping", RKLogLevelTrace) 的提示——它有助于分析实际发生​​的情况。

我仍然处于 RestKit 的“寻找我的方式”阶段，所以 YMMV。但是，根据this post by Blake 的说法，实际上看起来你需要两者——这是我可以让示例工作的唯一方法。但是，对相关对象的主键的引用是使用它的本地[即任务的 ivar] 属性来引用的：

        RKManagedObjectMapping* taskMapping = [RKManagedObjectMapping mappingForClass:[Task class]];
        [taskMapping mapKeyPath:@"id" toAttribute:@"taskID"];
        [taskMapping mapKeyPath:@"name" toAttribute:@"name"];
        [taskMapping mapKeyPath:@"assigned_user_id" toAttribute:@"assignedUserID"];
        taskMapping.primaryKeyAttribute = @"taskID";

        RKManagedObjectMapping* userMapping = [RKManagedObjectMapping mappingForClass:[User class]];
        [userMapping mapAttributes:@"name", @"email", nil];
        [userMapping mapKeyPath:@"id" toAttribute:@"userID"];
        [userMapping mapRelationship:@"tasks" withMapping:taskMapping];
        userMapping.primaryKeyAttribute = @"userID";
        [objectManager.mappingProvider setMapping:userMapping forKeyPath:@"user"];

        [taskMapping mapRelationship:@"assignedUser" withMapping:userMapping];
        [taskMapping connectRelationship:@"assignedUser" withObjectForPrimaryKeyAttribute:@"assignedUserID"];
        [objectManager.mappingProvider setMapping:taskMapping forKeyPath:@"task"]; 

这是在大约 3 天前从 master 拉取的。

【讨论】：

这个答案正确地将用户添加到任务中，但没有将任务添加到用户中。迭代项目现在可以正确显示任务的用户名。但是，无法迭代给定用户的任务。

【参考方案2】：

用户->任务映射是在userMapping上设置的，行[userMapping mapRelationship:@"tasks" withMapping:taskMapping];。我假设您是在说没有创建逆？

如果这是问题所在，我想你会发现 this commit 解决了这个问题，尽管我自己还没有尝试过。 （您可以在此时拉出树，或者更好地拉出当前的主分支）。

除此之外，[taskMapping connectRelationship:@"assignedUser" withObjectForPrimaryKeyAttribute:@"assignedUserID"]; 行有问题，它正在搜索主键属性为“assignedUserID”的对象，但查看其他映射，不存在这样的对象。请注意，在 userMapping 上，主键由 [userMapping setPrimaryKeyAttribute:@"userID"]; 定义

你可能想要[taskMapping connectRelationship:@"assignedUser" withObjectForPrimaryKeyAttribute:@"userID"];，或者更好的[taskMapping mapRelationship:@"assignedUser" withMapping:userMapping];

（通过我链接的提交，我什至不确定是否有必要添加任何东西来获得相反的结果 - 你可以同时尝试看看。）

如果仍有问题，您可以使用 RKLogConfigureByName("RestKit/ObjectMapping", RKLogLevelTrace); 为 ObjectMapper 打开日志

【参考方案3】：

我一直在弄乱这段代码将近一个半小时，终于让它工作了。我采取的步骤： 1）重新排列关系的创建，如下所示 2) 取消选中 RKRelationshipMappingExample.xcdatamodel > task.assignedUser 关系的“可选”复选标记。我注意到它既是“可选”又是最小 1，最大 1。我在此更改后删除了应用程序并重新安装它。现在用户被添加到任务和任务到用户！

- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil 
    self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
    if (self) 
        RKObjectManager* objectManager = [RKObjectManager objectManagerWithBaseURL:gRKCatalogBaseURL];
        objectManager.objectStore = [RKManagedObjectStore objectStoreWithStoreFilename:@"RKRelationshipMappingExample.sqlite"];


        RKManagedObjectMapping* taskMapping = [RKManagedObjectMapping mappingForClass:[Task class]];
        [taskMapping mapKeyPath:@"id" toAttribute:@"taskID"];
        [taskMapping mapKeyPath:@"name" toAttribute:@"name"];
        [taskMapping mapKeyPath:@"assigned_user_id" toAttribute:@"assignedUserID"];
        taskMapping.primaryKeyAttribute = @"taskID";

        RKManagedObjectMapping* userMapping = [RKManagedObjectMapping mappingForClass:[User class]];
        [userMapping mapAttributes:@"name", @"email", nil];
        [userMapping mapKeyPath:@"id" toAttribute:@"userID"];

        userMapping.primaryKeyAttribute = @"userID";
        [objectManager.mappingProvider setMapping:userMapping forKeyPath:@"user"];
        [objectManager.mappingProvider setMapping:taskMapping forKeyPath:@"task"];

        [userMapping mapRelationship:@"tasks" withMapping:taskMapping];        
        [taskMapping mapRelationship:@"assignedUser" withMapping:userMapping];

        [taskMapping connectRelationship:@"assignedUser" withObjectForPrimaryKeyAttribute:@"assignedUserID"];


        // NOTE - Project is not backed by Core Data
        RKObjectMapping* projectMapping = [RKObjectMapping mappingForClass:[Project class]];
        [projectMapping mapKeyPath:@"id" toAttribute:@"projectID"];
        [projectMapping mapAttributes:@"name", @"description", nil];
        [projectMapping mapRelationship:@"user" withMapping:userMapping];
        [projectMapping mapRelationship:@"tasks" withMapping:taskMapping];
        [objectManager.mappingProvider setMapping:projectMapping forKeyPath:@"project"];



    

    return self;


//to see NSLog messages, change the LOGGER_DEBUG to 2 (in LoggerClient.m) like this:
#define LOGGER_DEBUG 2
#ifdef NSLog
    #undef NSLog
#endif



//test method to make sure all relationships are created.
- (void)objectLoader:(RKObjectLoader *)objectLoader didLoadObjects:(NSArray *)objects 
    _objects = [objects retain];

    for(Project* managedObject in objects)
       NSLog(@" project user: %@", [managedObject.user description]);
        NSLog(@"###### user tasks count: %i",[managedObject.user.tasks  count]);
        for(Task* task in managedObject.user.tasks)
        
            NSLog(@"+++++managedObject.user.tasks: %@", [task description]);
        

        for(Task* task in managedObject.tasks)
        
            NSLog(@"*****task: %@", [task description]);
        

    
    [self.tableView reloadData];

【讨论】：

很好地抓住了核心数据属性——在看到您对我的帖子的评论后，我正在研究同样的问题，认为它必须与实体之间的关系有关。尝试同时学习 RestKit 和 Core Data 有点挑战！顺便说一句，不需要重新排列代码。

嗯——不幸的是，这看起来比现在更有希望。第一次在全新安装上正确加载水合物对象图，但随后的调用显示 user.tasks NSSet 的相同关系错误。我在 Task 实体的 assignedUser 的“可选”标志上打开和关闭了很多次，但我无法获得可重复的正确行为。

已确认——语句顺序和可选标志与此问题无关——请参阅我的更新答案