iOS Restkit如何關聯映射實體

Question

我有2個實體：Article和Category。

//Article mapping 
RKManagedObjectMapping *categoryMapping = [RKManagedObjectMapping mappingForClass:[Category class] inManagedObjectStore: objectManager.objectStore]; 
categoryMapping.primaryKeyAttribute = @"categoryId"; 
[categoryMapping mapKeyPathsToAttributes: 
@"CategoryId",@"categoryId", 
@"CategoryName",@"categoryName", 
nil]; 

//Category mapping 
RKManagedObjectMapping *articleMapping = [RKManagedObjectMapping mappingForClass:[Article class] inManagedObjectStore: objectManager.objectStore]; 
articleMapping.primaryKeyAttribute = @"articleId"; 
[articleMapping mapKeyPathsToAttributes: 
@"ArticleId",@"articleId", 
@"ArticleName",@"articleName", 
@"ArticleText",@"articleText", 
@"CategoryId",@"categoryId", 
nil]; 

//relationship mapping 
[categoryMapping mapRelationship:@"articles" withMapping:articleMapping]; 
[articleMapping mapRelationship:@"category" withMapping:categoryMapping]; 
[articleMapping connectRelationship:@"category" withObjectForPrimaryKeyAttribute:@"categoryId"]; 

//set mapping 
[objectManager.mappingProvider setMapping:articleMapping forKeyPath:@"article"]; 
[objectManager.mappingProvider setMapping:categoryMapping forKeyPath:@"category"]; 

那麼我想知道文章的範疇，但它等於空：

Article* article = [[Article allObjects] objectAtIndex:0]; 
    //article.category == nil 

article.categoryId和category.categoryId是相等的。

爲什麼映射關係不起作用？以這種方式

[categoryMapping mapKeyPath:@"articles" toRelationship:@"articles" withMapping:articleMapping]; 
[articleMapping mapKeyPath:@"category" toRelationship:@"category" withMapping:categoryMapping]; 

Answer 1

嘗試關係映射這是工作非常適合我。我在兩個項目中使用了它。