谓词与排序描述符
筛选并排序获取的结果。
谓词与排序描述符 是 CoddyKit 上的免费 SwiftUI Academy 课时。 这是第 4 节课，共 4 节。 你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。 这是 SwiftUI Academy 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 SwiftUI Academy 课程共包含 4 节课。
本课时的部分内容尚未翻译，以英文显示。
Shaping Your Results
As data grows you rarely want every row. Predicates and sort descriptors let you fetch just the right slice.
What a Predicate Is
An NSPredicate is a rule that decides which records match, written in a compact query-like format string.
NSPredicate(format: "isDone == true")Comparing Values
Use operators like ==, >, and < in the format string to match numbers, dates, and other fields.
NSPredicate(format: "priority > 2")Safe Arguments
Insert dynamic values with %@ placeholders instead of string-building, which is safer and clearer.
NSPredicate(format: "title == %@", searchText)Text Matching
Match partial text with CONTAINS, and add [c] to ignore case for friendly search.
NSPredicate(format: "title CONTAINS[c] %@", query)Combining Conditions
Join rules with AND and OR to express more specific filters in one predicate.
NSPredicate(format: "isDone == false AND priority > 1")What a Sort Descriptor Is
A SortDescriptor tells Core Data which attribute orders the rows, and in which direction.
SortDescriptor(\.title, order: .forward)Multiple Sort Keys
Pass an array of descriptors to break ties, like sorting by priority first, then by name.
[SortDescriptor(\.priority), SortDescriptor(\.title)]Using Them in @FetchRequest
Combine both in a @FetchRequest to fetch a filtered, ordered set right inside your view.
@FetchRequest(sortDescriptors: [SortDescriptor(\.title)], predicate: NSPredicate(format: "isDone == false")) var tasks: FetchedResults<Task>Filtering Beats Looping
Letting the store filter and sort is faster than fetching everything and trimming it in Swift. ⚡
Update Filters Live
You can rebuild a predicate from a search field and reassign it, so results refine as the user types.
Quick Check
You can now filter and order data. Quick check on the tools.
Recap
You used predicates to filter records and sort descriptors to order them, fetching exactly the data each screen needs. ✨
常见问题解答
「谓词与排序描述符」课时是免费的吗？
是的 — 「谓词与排序描述符」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 SwiftUI Academy 课程的其余内容，请升级到 CoddyKit PRO。 SwiftUI Academy 课程共包含 4 节课。
「谓词与排序描述符」这节课中我会学到什么？
筛选并排序获取的结果。 你通过在浏览器中直接运行的动手代码来练习 SwiftUI Academy，全天候 AI 导师会在你学习这节课的过程中回答你的问题。
学习 SwiftUI Academy 需要有经验吗？
无需任何先前经验。CoddyKit 上的 SwiftUI Academy 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。 这是第 4 节课，共 4 节。
「谓词与排序描述符」课时需要多长时间？
大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。
我能在这节 SwiftUI Academy 课中编写并运行代码吗？
能。每节 SwiftUI Academy 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。