问题描述
我有（我猜）典型的问题。我的核心数据数据库包含表，它们有BLOB字段和相当长的文本字段。
I have (I guess) typical problem. My Core Data database contains table, which have BLOB fields and quite long text fields.
通常我不需要加载这些大字段。由于在数据库中有几千条记录，我更喜欢只获取我真正需要的数据。换句话说，我想要SELECT name，id FROM TAB_NAME查询，而不是SELECT * FROM TAB_NAME查询。
Usually I do not need to load agrresivly those large size fields. Since there are several thousand records in a database I would prefer to fetch only data I truly need. In other words I would like to make "SELECT name, id FROM TAB_NAME" query, not "SELECT * FROM TAB_NAME" query.
有任何方法，字段使用Core Data？或者我应该寻找一些其他选项，例如，将大字段分隔到另一个表？也许有更好的（更简单）的方法来做到这一点？
Is there any way to fetch only selected fields using Core Data? Or shall I look for some other option, like, for instance, seperate large fields to another table? Maybe there is a better (easier) way to do this?
我习惯于使用Hibernate或JPA，它很容易做上述操作，核心数据文档我没有看到这样的选项。
I am used to working with Hibernate or JPA, where it easy to do described above operation, after going through Core Data docs I do not see such option.
推荐答案
此问题的答案已被接受，但FYI，这里是如何获取一个实体的特定属性与Core Data，而不重新考虑你的模型：
The answer to this question was accepted, but FYI, here's how to fetch only specific properties of an entity with Core Data, without re-factoring your model:
// build your NSFetchRequest
// ...
[request setResultType:NSDictionaryResultType];
[request setPropertiesToFetch:
[NSArray arrayWithObjects:@"property1", @"property2", /* etc. */ nil]];
另请参阅。
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