RestKit - 與關係映射映射單個源向多個目的地

Question

鑑於下列核心數據關係：

• Recipe <<---> Cookbook
• Recipe <<---> Author
• Cookbook <<---> Author

和表示配方此源JSON：

{ 
    "id": 123, 
    "name": "Recipe Name", 
    "author": { 
    "id": 456, 
    "name": "Author Name" 
    }, 
    "cookbook": { 
    "id": 789, 
    "title": "Cookbook Title" 
    } 
} 

我正在尋找一個RestKit映射，這將導致一個配方，其中具備以下條件：

• recipe.cookbook IN recipe.author.cookbooks
• recipe.cookbook.author === recipe.author

這是我到目前爲止有：

recipeMapping = 
    [RKEntityMapping mappingForEntityForName:@"Recipe" inManagedObjectStore:_store]; 
[recipeMapping addAttributeMappingsFromDictionary:@{ 
    @"id": @"id", 
    @"name": @"name" 
}]; 
recipeMapping.identificationAttributes = @[@"id"]; 

RKEntityMapping *authorMapping = 
    [RKEntityMapping mappingForEntityForName:@"Author" inManagedObjectStore:_store]; 
[authorMapping addAttributeMappingsFromDictionary:@{ 
    @"id": @"id", 
    @"name": @"name" 
}]; 
authorMapping.identificationAttributes = @[@"id"]; 

RKEntityMapping *cookbookMapping = 
    [RKEntityMapping mappingForEntityForName:@"Cookbook" inManagedObjectStore:_store]; 
[cookbookMapping addAttributeMappingsFromDictionary:@{ 
    @"id": @"id", 
    @"title": @"title" 
}]; 
cookbookMapping.identificationAttributes = @[@"id"]; 

[recipeMapping 
    addRelationshipMappingWithSourceKeyPath:@"cookbook" 
            mapping:cookbookMapping]; 
[recipeMapping 
    addRelationshipMappingWithSourceKeyPath:@"author" 
            mapping:authorMapping]; 

// Now what? 

一旦應用此映射，recipe.cookbook是一個道具例如Cookbook和recipe.author是Author的適當實例，但當然recipe.cookbook.author是零，並且recipe.author.cookbooks是空的。

Answer 1

因爲您沒有所需的信息，您無法在映射時真正做到這一點。

您可能可以設置使用外鍵的關係，而不是使用外鍵的特殊屬性，而是使用3個對象之間的關係。我會說這會有點脆弱，因爲它依賴於映射過程中處理關係的順序。我會考慮在後期處理過程中（即在映射完成後的回調中，或通過在受管對象子類上實現willSave）或在實際需要知道關係時按需執行此操作。這可以使用KVC做，是這樣的：

如果執行抓取來獲取所有的作者，你可以建立食譜，爲每個：

author.cookbooks = [author.recipes valueForKeyPath:@"@distinctUnionOfObjects.cookbooks"];