blocks|key|433802|text|因此，NSManagedObject与核心数据一起使用。创建模型，在模型中创建关系，然后让Xcode为您创建NSManagedObject类。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|433803|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

<p>So a NSManagedObject is used in conjunction with Core Data. Create your model, create the relationships in that model and then have Xcode create your NSManagedObject classes for you. </p>


blocks|key|433854|text|"NSArray是表示关系数据的正确方法吗？“|type|unstyled|depth|inlineStyleRanges|entityRanges|data|433855|NSSet用于在NSManagedObject子类中建模关系。NSArray用于获取属性，这是一种弱关系。|offset|length|style|CODE|433856|通常，您将使用内置于Xcode中的核心数据模型编辑器修改模型，然后让Xcode生成NSManagedObject子类文件作为模板供您使用。这将自动为关系生成NSSet属性(但遗憾的是，将不会自动为获取的属性生成属性。+)。|433857|“当我用用户标识取一个农民时，是否会自动发生级联，使我也能免费得到属于这个农民的所有牲畜实体？”|433858|当对象被获取时，它们的关系就是“错误”。对象图将只有对象在关系的目标上的占位符，直到它们被访问。这有助于限制内存对象图的大小，也是Core数据非常擅长的东西。您可以选择在获取中包含关系的目标，方法是设置适当的关系关键路径，以便使用setRelationshipKeyPathsForPrefetching:获取获取请求。|433859|entityMap|0|LINK|mutability|MUTABLE|url|https://developer.apple.com/library/ios/recipes/xcode_help-core_data_modeling_tool/Articles/about_cd_modeling_tool.html|1|http://www.openradar.me/radar?id=5232274786222080^0|0|0|5|8|F|V|7|0|15|F|26|5|7|J|0|2K|G|1|0|0|37|12|0^^$0|@$1|2|3|4|5|6|7|X|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|Y|8|@$D|Z|E|10|F|G]|$D|11|E|12|F|G]|$D|13|E|14|F|G]]|9|@]|A|$]]|$1|H|3|I|5|6|7|15|8|@$D|16|E|17|F|G]|$D|18|E|19|F|G]]|9|@$D|1A|E|1B|1|1C]|$D|1D|E|1E|1|1F]]|A|$]]|$1|J|3|K|5|6|7|1G|8|@]|9|@]|A|$]]|$1|L|3|M|5|6|7|1H|8|@$D|1I|E|1J|F|G]]|9|@]|A|$]]|$1|N|3|-4|5|6|7|1K|8|@]|9|@]|A|$]]]|O|$P|$5|Q|R|S|A|$T|U]]|V|$5|Q|R|S|A|$T|W]]]]

<h3>"NSArray the correct way to represent the relationship data?"</h3>

<p><code>NSSet</code> is used to model relationships in an <code>NSManagedObject</code> subclass. <code>NSArray</code> is used for fetched properties, which are a kind of weak relationship. </p>

<p>Typically you would use the <a href="https://developer.apple.com/library/ios/recipes/xcode_help-core_data_modeling_tool/Articles/about_cd_modeling_tool.html" rel="nofollow">Core Data Model Editor built into Xcode</a> to modify your model, and then have Xcode generate the <code>NSManagedObject</code> subclass files as a template for you to work with. This would automatically generate <code>NSSet</code> properties for relationships (but, sadly, <a href="http://www.openradar.me/radar?id=5232274786222080" rel="nofollow">will not automatically generate properties for fetched properties</a> ).</p>

<h3>"when I fetch a farmer by userid, does cascading automatically occur such that I also get all the Livestock entities belonging to this farmer for free?"</h3>

<p>When objects are fetched their relationships are "faults". The object graph will only have placeholders for the objects at the target of the relationship until they are accessed. This helps limit the size of the in-memory object graph, and is something that Core Data is very good at. You can choose to include the targets of relationships in a fetch by setting the appropriate relationship key paths for fetching on your fetch request using <code>setRelationshipKeyPathsForPrefetching:</code>.</p>


blocks|key|433896|text|下面的链接提供了一个基本教程，用于执行您所要求的操作：http://code.tutsplus.com/tutorials/core-data-from-scratch-subclassing-nsmanagedobject--cms-21880|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|433897|entityMap|0|LINK|mutability|MUTABLE|url|http://code.tutsplus.com/tutorials/core-data-from-scratch-subclassing-nsmanagedobject--cms-21880^0|R|2O|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

<p>The following link has a basic tutorial for doing what you are asking: <a href="http://code.tutsplus.com/tutorials/core-data-from-scratch-subclassing-nsmanagedobject--cms-21880" rel="nofollow">http://code.tutsplus.com/tutorials/core-data-from-scratch-subclassing-nsmanagedobject--cms-21880</a></p>


<p>I have two entities: Farmer, Livestock. a farmer has a one-to-many relationship with livestocks. So that each farmer may have a name, address, userid, pig set, chicken set, cow set.</p>

<p>I need to create a custom managed object class for farmer as</p>

<pre><code>@interface ManagedFarmer : NSManagedObject

@property (nonatomic, strong) NSString *name;

@property (nonatomic, strong) NSDate *date;

@property (nonatomic, strong) NSString *address;

@property (nonatomic, strong) NSNumber *userid;

@property (nonatomic, strong) NSArray *cows;//? set of cows: relationship to Livestock entity, designated cows

@property (nonatomic, strong) NSArray *chickens;//? 1-to-many relationship to Livestock entity, designated as chickens: 
@property (nonatomic, strong) NSArray *pigs;
</code></pre>

<ul>
<li>is NSArray the correct way to represent the relationship data?</li>
<li>when I fetch a farmer by userid, does cascading automatically occur such that I also get all the Livestock entities belonging to this farmer for free? </li>
</ul>


How do I map relationships in Custom NSManagedObject class

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

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我有两个实体:农夫，牲畜。农民与畜牧有一对多的关系。这样，每个农民都可以有一个名字，地址，用户标识，猪套，鸡套，牛套。我需要为农民创建一个自定义托管对象类，如@interface ManagedFarmer : NSManagedObject@property (nonatomic, strong) NSString ...

问如何映射自定义NSManagedObject类中的关系
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