RestKit反射关系实体无限循环

Question

这是RestKit中的错误还是我没有正确配置它？当使用以下映射时，我得到了一个无限循环：

JSON:

[
{
    "name": "Test 1",
    "subtests": [
        {
            "name": "Subtest 1"
        },
        {
            "name": "Subtest 2"
        },
        {
            "name": "Subtest 3"
        }
    ],
    "children": ["Test 1"]
},
{
    "name": "Test 2",
    "subtests": [
        {
            "name": "Subtest 4"
        },
        {
            "name": "Subtest 5"
        },
        {
            "name": "Subtest 6"
        }
    ],
    "children": ["Test 2"]
}
]

地图提供商：

+ (RKMapping *)testMapping
{
    RKEntityMapping *mapping = [RKEntityMapping mappingForEntityForName:NSStringFromClass([Test class]) inManagedObjectStore:[InfoDataModel sharedDataModel].objectStore];
    mapping.identificationAttributes = @[ @"name" ];
    [mapping addAttributeMappingsFromArray:@[ @"name" ]];
    [mapping addPropertyMapping:[RKRelationshipMapping relationshipMappingFromKeyPath:@"children" toKeyPath:@"children" withMapping:[MappingProvider reflexiveTestMapping]]];
    [mapping addPropertyMapping:[RKRelationshipMapping relationshipMappingFromKeyPath:@"subtests" toKeyPath:@"subtests" withMapping:[MappingProvider subTestMapping]]];
    return mapping;
}
+ (RKMapping *)reflexiveTestMapping
{
    RKEntityMapping *mapping = [RKEntityMapping mappingForEntityForName:NSStringFromClass([Test class]) inManagedObjectStore:[InfoDataModel sharedDataModel].objectStore];
    mapping.identificationAttributes = @[ @"name" ];
    [mapping addPropertyMapping:[RKRelationshipMapping relationshipMappingFromKeyPath:nil toKeyPath:@"name" withMapping:[MappingProvider testMapping]]];
    return mapping;
}
+ (RKMapping *)subTestMapping;
{
    RKEntityMapping *mapping = [RKEntityMapping mappingForEntityForName:NSStringFromClass([SubTest class]) inManagedObjectStore:[InfoDataModel sharedDataModel].objectStore];
    mapping.identificationAttributes = @[ @"name" ];
    [mapping addAttributeMappingsFromArray:@[ @"name" ]];
    return mapping;    
}

我在这里称之为：

- (IBAction)loadTestAndSubtestEntity:(id)sender {
    RKLogConfigureByName("RestKit", RKLogLevelWarning);
    RKLogConfigureByName("RestKit/ObjectMapping", RKLogLevelTrace);
    RKLogConfigureByName("RestKit/Network", RKLogLevelTrace);
    NSString *filePathComponent = [self.pathComponent     stringByAppendingPathComponent:@"test.json"];
    [[InfoDataModel sharedDataModel] importDataFromJsonFilePathComponent:filePathComponent withMapping:[MappingProvider testMapping]];
}

由于挂起，因此不会生成任何输出：self.storePath是用文件路径初始化的。

- (void)importDataFromJsonFilePathComponent:(NSString *)jsonFilePathComponent withMapping:(RKMapping *)mapping
{
    if (self.storePath) {
        NSString *jsonFilePath = [RKApplicationDataDirectory() stringByAppendingPathComponent:jsonFilePathComponent];
        MyLog(@"InfoDataModel. JSON file: %@", jsonFilePath);
        RKManagedObjectImporter *importer = [[RKManagedObjectImporter alloc] initWithManagedObjectModel:self.objectStore.managedObjectModel storePath:self.storePath];
        importer.resetsStoreBeforeImporting = NO;
        MyLog(@"InfoDataModel. Store: %@", self.storePath);
        NSError *error = nil;
        [importer importObjectsFromItemAtPath:jsonFilePath
                                  withMapping:mapping
                                      keyPath:nil
                                        error:&error];
        BOOL success = [importer finishImporting:&error];
        if (success) {
            [importer logSeedingInfo];
        }
    }
}

Answer 1

问题是有两个方法在相互调用。由于以下行，testMapping方法调用reflexiveTestMapping方法：

[mapping addPropertyMapping:[RKRelationshipMapping relationshipMappingFromKeyPath:@"children" toKeyPath:@"children" withMapping:[MappingProvider reflexiveTestMapping]]];

并且reflexiveTestMapping方法调用testMapping方法是由于以下行：

[mapping addPropertyMapping:[RKRelationshipMapping relationshipMappingFromKeyPath:nil toKeyPath:@"name" withMapping:[MappingProvider testMapping]]];

这是一个硬循环，与映射没有直接关系，只是与您尝试创建映射的方式有关。

映射不需要以这种方式创建，因为JSON中的children关系只包含名称，而不包含完整对象。

Answer 2

此递归的一个"解决方案"是限制基于在估计的跳跃上，在这种情况下是两次跳跃。

+ (RKMapping *)reflexiveTestMapping
{
    RKEntityMapping *mapping = [RKEntityMapping mappingForEntityForName:NSStringFromClass([Test class]) inManagedObjectStore:[InfoDataModel sharedDataModel].objectStore];
    mapping.identificationAttributes = @[ @"name" ];
    // No more recursion calls from this point
    return mapping;
}

Answer 3

这就是我修复递归的方法：

+ (RKMapping *)testMapping
{
    RKEntityMapping *innerMapping = [RKEntityMapping mappingForEntityForName:NSStringFromClass([Test class]) inManagedObjectStore:[InfoDataModel sharedDataModel].objectStore];
    innerMapping.identificationAttributes = @[ @"name" ];
    RKEntityMapping *mapping = [RKEntityMapping mappingForEntityForName:NSStringFromClass([Test class]) inManagedObjectStore:[InfoDataModel sharedDataModel].objectStore];
    mapping.identificationAttributes = @[ @"name" ];
    [mapping addAttributeMappingsFromArray:@[ @"name" ]];
    [mapping addPropertyMapping:[RKRelationshipMapping relationshipMappingFromKeyPath:@"children" toKeyPath:@"children" withMapping:innerMapping]];
    return mapping;
}

Answer 4

这就是我对swift 所做的

class var keyAll: [String] {
    return [
      "title",
      "desc"
    ]
  }
  class var objectMapping: RKObjectMapping {
    let childMapping = RKObjectMapping(forClass: Category.self)
    childMapping.addAttributeMappingsFromArray(keyAll)
    let mapping = RKObjectMapping(forClass: Category.self)
    mapping.addAttributeMappingsFromArray(keyAll)
    mapping.addPropertyMapping(RKRelationshipMapping(fromKeyPath: keyChilds, toKeyPath: keyChilds, withMapping: childMapping))
    return mapping
  }