-
Notifications
You must be signed in to change notification settings - Fork 411
Commit
This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.
- Loading branch information
Showing
35 changed files
with
171 additions
and
53 deletions.
There are no files selected for viewing
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
97 changes: 97 additions & 0 deletions
97
SwiftPamphletApp/Resource/Guide/SwiftData/SwiftData-检索(ap).md
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,97 @@ | ||
|
|
||
| ## `@Query` | ||
| 使用 `@Query` 会从数据库中获取数据。 | ||
|
|
||
| ```swift | ||
| @Query private var articles: [Article] | ||
| ``` | ||
|
|
||
| `@Query` 还支持 filter、sort、order 和 animation 等参数。 | ||
|
|
||
| ```swift | ||
| @Query(sort: \Article.title, order: .forward) private var articles: [Article] | ||
| ``` | ||
|
|
||
| sort 可支持多个 SortDescriptor，SwiftData 会按顺序处理。 | ||
|
|
||
| ```swift | ||
| @Query(sort: [SortDescriptor(\Article.isArchived, order: .forward),SortDescriptor(\Article.updateDate, order: .reverse)]) var articles: [Article] | ||
| ``` | ||
|
|
||
| ## Predicate | ||
|
|
||
| filter 使用的是 `#Predicate` | ||
|
|
||
| ```swift | ||
| static var now: Date { Date.now } | ||
|
|
||
| @Query(filter: #Predicate<Article> { article in | ||
| article.releaseDate > now | ||
| }) var draftArticles: [Article] | ||
| ``` | ||
|
|
||
| Predicate 支持的内置方法主要有 `contains`、`allSatisfy`、`flatMap`、`filter`、`subscript`、`starts`、`min`、`max`、`localizedStandardContains`、`localizedCompare`、`caseInsensitiveCompare` 等。 | ||
|
|
||
| ```swift | ||
| @Query(filter: #Predicate<Article> { article in | ||
| article.title.starts(with: "苹果发布会") | ||
| }) var articles: [Article] | ||
| ``` | ||
|
|
||
| 需要注意的是 `.isEmpty` 不能使用 `article.title.isEmpty == false` ，否则会崩溃。 | ||
|
|
||
| ## FetchDescriptor | ||
|
|
||
| FetchDescriptor 可以在模型中查找数据，而不必在视图层做。 | ||
|
|
||
| ```swift | ||
| @Model | ||
| final class Article { | ||
| var title: String | ||
| ... | ||
| static var all: FetchDescriptor<Article> { | ||
| FetchDescriptor(sortBy: [SortDescriptor(\Article.updateDate, order: .reverse)]) | ||
| } | ||
| } | ||
|
|
||
| struct SomeView: View { | ||
| @Query(Article.all) private var articles: [Article] | ||
| ... | ||
| } | ||
| ``` | ||
|
|
||
| ## 获取数量而不加载 | ||
|
|
||
| 使用 `fetchCount()` 方法，可完成整个计数，且很快，内存占用少。 | ||
|
|
||
| ```swift | ||
| let descriptor = FetchDescriptor<Article>(predicate: #Predicate { $0.words > 50 }) | ||
| let count = (try? modelContext.fetchCount(descriptor)) ?? 0 | ||
| ``` | ||
|
|
||
| ## fetchLimit 限制获取数量 | ||
|
|
||
| ```swift | ||
| var descriptor = FetchDescriptor<Article>( | ||
| predicate: #Predicate { $0.read }, | ||
| sortBy: [SortDescriptor(\Article.updateDate, | ||
| order: .reverse)]) | ||
| descriptor.fetchLimit = 30 | ||
| let articles = try context.fetch(descriptor) | ||
|
|
||
| // 翻页 | ||
| let pSize = 30 | ||
| let pNumber = 1 | ||
| var fetchDescriptor = FetchDescriptor<Article>(sortBy: [SortDescriptor(\Article.updateDate, order: .reverse)]) | ||
| fetchDescriptor.fetchOffset = pNumber * pSize | ||
| fetchDescriptor.fetchLimit = pSize | ||
| ``` | ||
|
|
||
| ## 限制获取的属性 | ||
|
|
||
| 只请求要用的属性 | ||
|
|
||
| ```swift | ||
| var fetchDescriptor = FetchDescriptor<Article>(sortBy: [SortDescriptor(\.updateDate, order: .reverse)]) | ||
| fetchDescriptor.propertiesToFetch = [\.title, \.updateDate] | ||
| ``` |
This file was deleted.
Oops, something went wrong.
2 changes: 0 additions & 2 deletions
2
SwiftPamphletApp/Resource/Guide/SwiftData/检索FetchDescriptor(ap).md
This file was deleted.
Oops, something went wrong.
File renamed without changes.
File renamed without changes.
File renamed without changes.
File renamed without changes.
File renamed without changes.
File renamed without changes.
File renamed without changes.
File renamed without changes.
File renamed without changes.
File renamed without changes.
File renamed without changes.
File renamed without changes.
File renamed without changes.
File renamed without changes.
File renamed without changes.
File renamed without changes.
File renamed without changes.
File renamed without changes.
File renamed without changes.
File renamed without changes.
File renamed without changes.
File renamed without changes.
File renamed without changes.
File renamed without changes.
File renamed without changes.
File renamed without changes.
File renamed without changes.
File renamed without changes.
File renamed without changes.
File renamed without changes.