Objective C + RESTKit：获取对象的问题

Posted 2023-02-23

【中文标题】Objective C + RESTKit：获取对象的问题

【英文标题】：Objective C + RESTKit: Problems with getting Objects

【发布时间】：2012-05-02 07:36:45

【问题描述】：

我想将 RestKit 用于 Restful Web 服务，以便在 LAMP 环境和 ios 应用程序之间进行通信。 因此，我进行了第一次测试，以检查是否一切都如可用教程和 RestKit 页面中所述。

现在代码如下所示：

RKObjectManager* objectManager = [RKObjectManager managerWithBaseURLString:@"http://localhost/resttest"];

objectManager.client.requestQueue.showsNetworkActivityIndicatorWhenBusy = YES;

#ifdef RESTKIT_GENERATE_SEED_DB
    NSString *seedDatabaseName = nil;
    NSString *databaseName = RKDefaultSeedDatabaseFileName;
#else
    NSString *seedDatabaseName = RKDefaultSeedDatabaseFileName;
    NSString *databaseName = @"CoreData.sqlite";
#endif

objectManager.objectStore = [RKManagedObjectStore objectStoreWithStoreFilename:databaseName usingSeedDatabaseName:seedDatabaseName managedObjectModel:nil delegate:self];

// Map Person Object
RKManagedObjectMapping *personMapping = [RKManagedObjectMapping mappingForClass:[Person class] inManagedObjectStore:objectManager.objectStore];
//RKManagedObjectMapping *personMapping = [RKManagedObjectMapping mappingForEntityWithName:@"Person" inManagedObjectStore:[RKObjectManager sharedManager].objectStore];
[personMapping mapKeyPath:@"id" toAttribute:@"person_id"];
[personMapping mapKeyPath:@"firstname" toAttribute:@"person_firstname"];
[personMapping mapKeyPath:@"lastname" toAttribute:@"person_lastname"];
[personMapping mapKeyPath:@"gender" toAttribute:@"person_gender"];
personMapping.primaryKeyAttribute = @"id";


// Register our mappings with the provider;    
[objectManager.mappingProvider setMapping:personMapping forKeyPath:@"/person"];
objectManager.acceptMIMEType = RKMIMETypeJSON;

#ifdef RESTKIT_GENERATE_SEED_DB
    RKLogConfigureByName("RestKit/ObjectMapping", RKLogLevelInfo);
    RKLogConfigureByName("RestKit/CoreData", RKLogLevelTrace);
#endif

[objectManager loadObjectsAtResourcePath:@"/person" delegate:self];

这就是我的托管对象的样子：

@interface Person : NSManagedObject

@property (nonatomic, retain) NSString * person_firstname;
@property (nonatomic, retain) NSString * person_lastname;
@property (nonatomic, retain) NSString * person_gender;
@property (nonatomic, retain) NSNumber * person_id;

@end

这是服务器端的虚拟代码，它只返回一些 json 示例字符串：

<?php

    header('Content-type: application/json');

    if($_SERVER['REQUEST_METHOD'] == 'GET')
    
        $json_string = ' "persons": [
                             "id": "1",
                              "firstname": "hans",
                              "lastname": "maier",
                              "genre": "m"
                            ,
                             "id": "2",
                              "firstname": "michael",
                              "lastname": "schmidt",
                              "genre": "w"
                            ]
                        ';

        echo $json_string;
    

?>

获取返回的 json-String 的 URI 是 http://localhost/resttest/person(/index.php)。

我的问题是：

当我没有为''定义资源路径时，我总是得到这个错误：

E restkit.network:RKObjectLoader.m:216 在映射过程中遇到错误：找不到 keyPath 的对象映射：''

我不知道为什么会这样。我试过的其他例子都没有这个问题，但我不知道我做错了什么。

当它工作时（我必须将基本 URL 更改为 http://localhost/resttest/person），我得到一个空对象而不是错误。

我将不胜感激有关此主题的任何帮助，因为现在我不知道自己做错了什么。

谢谢！

编辑 03.05.2012：

这是我在日志中得到的：

2012-05-03 12:52:05.067 RESTKitCoreDataTest[5139:13807] D restkit.object_mapping:RKObjectMapper.m:320 Performing object mapping sourceObject: 
    persons =     (
                
            firstname = hans;
            gender = m;
            id = 1;
            lastname = maier;
        ,
                
            firstname = michael;
            gender = w;
            id = 2;
            lastname = schmidt;
        
    );

 and targetObject: (null)
2012-05-03 12:52:05.067 RESTKitCoreDataTest[5139:13807] T restkit.object_mapping:RKObjectMapper.m:278 Examining keyPath '' for mappable content...
2012-05-03 12:52:05.067 RESTKitCoreDataTest[5139:13807] D restkit.object_mapping:RKObjectMapper.m:264 Found mappable data at keyPath '': 
    persons =     (
                
            firstname = hans;
            gender = m;
            id = 1;
            lastname = maier;
        ,
                
            firstname = michael;
            gender = w;
            id = 2;
            lastname = schmidt;
        
    );

2012-05-03 12:52:05.073 RESTKitCoreDataTest[5139:13807] D restkit.object_mapping:RKObjectMapper.m:210 Asked to map source object 
    persons =     (
                
            firstname = hans;
            gender = m;
            id = 1;
            lastname = maier;
        ,
                
            firstname = michael;
            gender = w;
            id = 2;
            lastname = schmidt;
        
    );
 with mapping <RKManagedObjectMapping:0x811eb60 objectClass=Person keyPath mappings => (
    "RKObjectKeyPathMapping: id => person_id",
    "RKObjectKeyPathMapping: firstname => person_firstname",
    "RKObjectKeyPathMapping: lastname => person_lastname",
    "RKObjectKeyPathMapping: gender => person_gender"
)>
2012-05-03 12:52:05.074 RESTKitCoreDataTest[5139:13807] D restkit.object_mapping:RKObjectMappingOperation.m:617 Starting mapping operation...
2012-05-03 12:52:05.074 RESTKitCoreDataTest[5139:13807] T restkit.object_mapping:RKObjectMappingOperation.m:618 Performing mapping operation: RKObjectMappingOperation for 'Person' object. Mapping values from object 
    persons =     (
                
            firstname = hans;
            gender = m;
            id = 1;
            lastname = maier;
        ,
                
            firstname = michael;
            gender = w;
            id = 2;
            lastname = schmidt;
        
    );
 to object <Person: 0x6e295d0> (entity: Person; id: 0x6e29610 <x-coredata:///Person/t99EFF6DC-EBDA-405C-8AFF-D082E4A8542F2> ; data: 
    "person_firstname" = nil;
    "person_gender" = nil;
    "person_id" = 0;
    "person_lastname" = nil;
) with object mapping <RKManagedObjectMapping:0x811eb60 objectClass=Person keyPath mappings => (
    "RKObjectKeyPathMapping: id => person_id",
    "RKObjectKeyPathMapping: firstname => person_firstname",
    "RKObjectKeyPathMapping: lastname => person_lastname",
    "RKObjectKeyPathMapping: gender => person_gender"
)>
2012-05-03 12:52:05.074 RESTKitCoreDataTest[5139:13807] T restkit.object_mapping:RKObjectMappingOperation.m:388 Did not find mappable attribute value keyPath 'id'
2012-05-03 12:52:05.074 RESTKitCoreDataTest[5139:13807] T restkit.object_mapping:RKObjectMappingOperation.m:388 Did not find mappable attribute value keyPath 'firstname'
2012-05-03 12:52:05.075 RESTKitCoreDataTest[5139:13807] T restkit.object_mapping:RKObjectMappingOperation.m:388 Did not find mappable attribute value keyPath 'lastname'
2012-05-03 12:52:05.075 RESTKitCoreDataTest[5139:13807] T restkit.object_mapping:RKObjectMappingOperation.m:388 Did not find mappable attribute value keyPath 'gender'
2012-05-03 12:52:05.075 RESTKitCoreDataTest[5139:13807] D restkit.object_mapping:RKObjectMappingOperation.m:638 Mapping operation did not find any mappable content
2012-05-03 12:52:05.075 RESTKitCoreDataTest[5139:13807] T restkit.core_data:RKManagedObjectMappingOperation.m:98 relationshipsAndPrimaryKeyAttributes: 

2012-05-03 12:52:05.075 RESTKitCoreDataTest[5139:13807] D restkit.object_mapping:RKObjectMapper.m:351 The following operations are in the queue: (
)
2012-05-03 12:52:05.075 RESTKitCoreDataTest[5139:13807] D restkit.object_mapping:RKObjectMapper.m:366 Finished performing object mapping. Results: 

2012-05-03 12:52:05.080 RESTKitCoreDataTest[5139:fb03] Loaded persons: (
)

【问题讨论】：

您是否注意到您返回的json响应中的键与您在iOS中的映射不同。它是 iOS 中的性别，而 json 响应返回流派。还是这是拼写错误？？

你是对的，谢谢，但最终它并没有什么不同——同样的错误。我也用 XML-data 进行了尝试，映射是正确的，也没有发生任何事情。

尝试打开对象映射跟踪：RKLogConfigureByName("RestKit/ObjectMapping", RKLogLevelTrace);

感谢您的建议，保罗。我编辑了上面的文本以显示日志输出。

【参考方案1】：

可能性一：

您似乎将映射设置为错误的键路径。

试试

// Register our mappings with the provider;    
[objectManager.mappingProvider setMapping:personMapping forKeyPath:@"persons"];

并检查它是否有效。

可能性2：

在映射中指定 JSON 的根路径。

试试

// Map Person Object
RKManagedObjectMapping *personMapping = [RKManagedObjectMapping mappingForClass:[Person class] inManagedObjectStore:objectManager.objectStore];
[personMapping mapKeyPath:@"id" toAttribute:@"person_id"];
[personMapping mapKeyPath:@"firstname" toAttribute:@"person_firstname"];
[personMapping mapKeyPath:@"lastname" toAttribute:@"person_lastname"];
[personMapping mapKeyPath:@"gender" toAttribute:@"person_gender"];
personMapping.rootKeyPath = @"persons";
personMapping.primaryKeyAttribute = @"id";

并检查它是否有效。

【讨论】：

不，不幸的是它并没有改变任何东西。尽管如此，还是感谢您的回答。

用另一个想法更新了我的答案。我目前在我的项目中使用这两种方法。