add swiftUI code

2025-01-22 14:09:10 +08:00
parent 68e7b7347c
commit 8a99853829
2531 changed files with 486215 additions and 0 deletions
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+/// The `HasOneAssociation` indicates a one-to-one connection between two
+/// record types, such as each instance of the declaring record "has one"
+/// instances of the other record.
+///
+/// For example, if your application has one database table for countries, and
+/// another for their demographic profiles, you'd declare the association
+/// this way:
+///
+/// ```swift
+/// struct Demographics: TableRecord { }
+/// struct Country: TableRecord {
+///     static let demographics = hasOne(Demographics.self)
+/// }
+/// ```
+///
+/// A `HasOneAssociation` should be supported by an SQLite foreign key.
+///
+/// Foreign keys are the recommended way to declare relationships between
+/// database tables because not only will SQLite guarantee the integrity of your
+/// data, but GRDB will be able to use those foreign keys to automatically
+/// configure your associations.
+///
+/// You define the foreign key when you create database tables. For example:
+///
+/// ```swift
+/// try db.create(table: "country") { t in
+///     t.primaryKey("code", .text)                    // (1)
+///     t.column("name", .text)
+/// }
+/// try db.create(table: "demographics") { t in
+///     t.autoIncrementedPrimaryKey("id")
+///     t.belongsTo("country", onDelete: .cascade)     // (2)
+///         .notNull()                                 // (3)
+///         .unique()                                  // (4)
+///     t.column("population", .integer)
+///     t.column("density", .double)
+/// }
+/// ```
+///
+/// 1. The country table has a primary key.
+/// 2. The `demographics.countryCode` column is used to link a demographic
+///    profile to the country it belongs to. This column is indexed in order
+///    to ease the selection of the demographics of a country. A foreign key
+///    is defined from `demographics.countryCode` column to `country.code`,
+///    so that SQLite guarantees that no profile refers to a missing
+///    country. The `onDelete: .cascade` option has SQLite automatically
+///    delete a profile when its country is deleted. See
+///    <https://sqlite.org/foreignkeys.html#fk_actions> for more information.
+/// 3. Make the `demographics.countryCode` column not null if you want SQLite to
+///    guarantee that all profiles are linked to a country.
+/// 4. Create a unique index on the `demographics.countryCode` column in order
+///    to guarantee the unicity of any country's demographics.
+///
+/// The example above uses a string primary for the country table. But generally
+/// speaking, all primary keys are supported.
+///
+/// If the database schema does not define foreign keys between tables, you can
+/// still use `HasOneAssociation`. But your help is needed to define the
+/// missing foreign key:
+///
+/// ```swift
+/// struct Demographics: TableRecord { }
+/// struct Country: TableRecord {
+///     static let demographics = hasOne(Demographics.self, using: ForeignKey(...)
+/// }
+/// ```
+public struct HasOneAssociation<Origin, Destination> {
+    public var _sqlAssociation: _SQLAssociation
+    
+    init(
+        to destinationRelation: SQLRelation,
+        key: String?,
+        using foreignKey: ForeignKey?)
+    {
+        let destinationTable = destinationRelation.source.tableName
+        
+        let foreignKeyCondition = SQLForeignKeyCondition(
+            destinationTable: destinationTable,
+            foreignKey: foreignKey,
+            originIsLeft: false)
+        
+        let associationKey: SQLAssociationKey
+        if let key {
+            associationKey = .fixedSingular(key)
+        } else {
+            associationKey = .inflected(destinationTable)
+        }
+        
+        _sqlAssociation = _SQLAssociation(
+            key: associationKey,
+            condition: .foreignKey(foreignKeyCondition),
+            relation: destinationRelation,
+            cardinality: .toOne)
+    }
+}
+
+extension HasOneAssociation: AssociationToOne {
+    public typealias OriginRowDecoder = Origin
+    public typealias RowDecoder = Destination
+}