什么是核心数据源获取
What is Core Data Source Fetch
我正在查看 Xcode 中核心数据的 Entity Mapping 面板，注意到一个名为 Source Fetch 的设置.有两个选项 Default 和 Custom。 Source Fetch 是关于什么的？
You specify the sourceExpression for the mapping using a combination of the the source fetch popup menu and the text view beneath it. You can select either the default fetch—in which case you can optionally specify a filter predicate for the fetch—or a custom fetch, in which case you specify the source expression directly.
我正在查看 Xcode 中核心数据的 Entity Mapping 面板，注意到一个名为 Source Fetch 的设置.有两个选项 Default 和 Custom。 Source Fetch 是关于什么的？
You specify the sourceExpression for the mapping using a combination of the the source fetch popup menu and the text view beneath it. You can select either the default fetch—in which case you can optionally specify a filter predicate for the fetch—or a custom fetch, in which case you specify the source expression directly.