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‎Demo/StructuredQueriesExample/README.md‎

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# Structured Queries Example
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This used PowerSync along side the [structured-queries](https://github.com/pointfreeco/swift-structured-queries) library to perform DB operations using a typed query builder syntax.
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This demo can be executed with
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```bash
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swift run StructuredQueriesExample
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```

‎Demo/StructuredQueriesExample/Sources/entry.swift‎

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import Foundation
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import PowerSync
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import PowerSyncStructuredQueries
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import StructuredQueries
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@StructuredQueries.Table("users")
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struct User {
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var id: String
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var name: String
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var birthday: Date?
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}
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@StructuredQueries.Table("posts")
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struct Post {
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var id: String
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var description: String
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// TODO, inserts seem to break with this
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@StructuredQueries.Column("user_id")
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var userId: String
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}
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@main
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struct Main {
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static func main() async throws {
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// TODO, check if the schema can be shared in some way
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let powersync = PowerSyncDatabase(
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schema: Schema(
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tables: [
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Table(
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name: "users",
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columns: [
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.text("name"),
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.text("birthday"),
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]
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),
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Table(
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name: "posts",
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columns: [
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.text("description"),
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.text("user_id"),
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]
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),
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],
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),
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dbFilename: "test.sqlite"
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)
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let testUserID = UUID().uuidString
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try await User.insert {
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($0.id, $0.name, $0.birthday)
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} values: {
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(testUserID, "Steven", Date())
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}.execute(powersync)
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try await User.insert {
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User(
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id: UUID().uuidString,
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name: "Nevets"
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)
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}.execute(powersync)
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let users = try await User.all.fetchAll(powersync)
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print("The users are:")
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for user in users {
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print(user)
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}
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// TODO: column aliases seem to be broken
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// try await Post.insert { Post(
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// id: UUID().uuidString, description: "A Post", userId: testUserID
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// ) }.execute(powersync)
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// // TODO: fix typing in order to execute joined queries
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// let postsWithUsers = Post.join(User.all) { $0.userId == $1.id }
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// .select { ($0.description, $1.name) }
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}
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}

‎Package.resolved‎

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‎Package.swift‎

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@@ -62,8 +62,14 @@ let package = Package(
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name: packageName,
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targets: ["PowerSync"]
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),
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.library(
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name: "PowerSyncStructuredQueries",
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targets: ["PowerSyncStructuredQueries"]
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),
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],
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dependencies: conditionalDependencies,
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dependencies: [
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.package(url: "https://github.com/pointfreeco/swift-structured-queries", from: "0.4.0"),
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] + conditionalDependencies,
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targets: [
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// Targets are the basic building blocks of a package, defining a module or a test suite.
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// Targets can depend on other targets in this package and products from dependencies.
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name: "PowerSyncTests",
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dependencies: ["PowerSync"]
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),
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.target(
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name: "PowerSyncStructuredQueries",
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dependencies: [
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.byName(name: packageName),
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.product(name: "StructuredQueries", package: "swift-structured-queries"),
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],
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path: "Sources/StructuredQueries"
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),
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.executableTarget(
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name: "StructuredQueriesExample",
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dependencies: [
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.byName(name: "PowerSyncStructuredQueries"),
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],
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path: "Demo/StructuredQueriesExample"
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),
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] + conditionalTargets
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)

‎README.md‎

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@@ -10,16 +10,22 @@ This is the PowerSync SDK for Swift clients. The SDK reference is available [her
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## Structure: Packages
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- [Sources](./Sources/)
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- [Sources](./Sources/PowerSync)
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- This is the Swift SDK implementation.
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- [Sources](./Sources/StructuredQueries)
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- A typed query builder using [structured-queries](https://github.com/pointfreeco/swift-structured-queries).
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## Demo Apps / Example Projects
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The easiest way to test the PowerSync Swift SDK is to run our demo application.
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- [Demo/PowerSyncExample](./Demo/README.md): A simple to-do list application demonstrating the use of the PowerSync Swift SDK using a Supabase connector.
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- [Demo/StructuredQueriesExample](./Demo/StructuredQueriesExample/README.md): A simple Swift executable which uses the `PowerSyncStructuredQueries` library.
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## Installation
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Add

‎Sources/StructuredQueries/PowerSyncQueryDecoder.swift‎

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import Foundation
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import PowerSync
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import StructuredQueries
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@usableFromInline
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struct PowerSyncQueryDecoder: QueryDecoder {
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/// The structured queries library will decode the typed struct's columns in
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/// the same order which it compiled the SELECT statement's column list.
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/// The library will call the correct typed `decode` method, we just need to keep
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/// track of which column index we're on.
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@usableFromInline
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var currentIndex: Int = 0
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/// The PowerSync `SqlCursor` provided in the `mapper` closure.
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@usableFromInline
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var cursor: SqlCursor
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@usableFromInline
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init(cursor: SqlCursor) {
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self.cursor = cursor
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}
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/// Decodes a single tuple of the given type starting from the current column.
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///
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/// - Parameter columnTypes: The types to decode as.
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/// - Returns: A tuple of the requested types.
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@inlinable
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@inline(__always)
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public mutating func decodeColumns<each T: QueryRepresentable>(
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_: (repeat each T).Type
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) throws -> (repeat (each T).QueryOutput) {
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try (repeat (each T)(decoder: &self).queryOutput)
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}
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@inlinable
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mutating func decode(_: [UInt8].Type) throws -> [UInt8]? {
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defer { currentIndex += 1 }
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// TODO: blob support
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return nil
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}
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@inlinable
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mutating func decode(_: Bool.Type) throws -> Bool? {
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try decode(Int64.self).map { $0 != 0 }
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}
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@inlinable
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mutating func decode(_: Date.Type) throws -> Date? {
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try decode(String.self).map {
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let formatter = ISO8601DateFormatter()
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guard let date = formatter.date(from: $0) else {
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throw InvalidDate()
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}
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return date
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}
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}
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@inlinable
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mutating func decode(_: Double.Type) throws -> Double? {
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defer { currentIndex += 1 }
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return cursor.getDoubleOptional(index: currentIndex)
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}
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@inlinable
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mutating func decode(_: Int.Type) throws -> Int? {
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try decode(Int64.self).map(Int.init)
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}
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@inlinable
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mutating func decode(_: Int64.Type) throws -> Int64? {
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defer { currentIndex += 1 }
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return cursor.getInt64Optional(index: currentIndex)
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}
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@inlinable
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mutating func decode(_: String.Type) throws -> String? {
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defer { currentIndex += 1 }
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return cursor.getStringOptional(index: currentIndex)
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}
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@inlinable
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mutating func decode(_: UUID.Type) throws -> UUID? {
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guard let uuidString = try decode(String.self) else { return nil }
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guard let uuid = UUID(uuidString: uuidString) else { throw InvalidUUID() }
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return uuid
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}
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}
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@usableFromInline
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struct InvalidUUID: Error {
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@usableFromInline
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init() {}
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}
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@usableFromInline
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struct InvalidDate: Error {
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@usableFromInline
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init() {}
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}

‎Sources/StructuredQueries/QueryCursor.swift‎

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import Foundation
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import PowerSync
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import StructuredQueries
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/// The Structured Queries library is dialect agnostic.
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/// For our purposes, we can use "?" for placeholders.
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public extension QueryFragment {
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func prepareSqlite() -> (sql: String, bindings: [QueryBinding]) {
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return prepare { _ in "?" }
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}
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}
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@usableFromInline
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final class QueryValueCursor<QueryValue: QueryRepresentable> {
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public typealias Element = QueryValue.QueryOutput
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@usableFromInline
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let powerSync: PowerSyncDatabaseProtocol
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@usableFromInline
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let query: QueryFragment
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@usableFromInline
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init(powerSync: PowerSyncDatabaseProtocol, query: QueryFragment) throws {
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self.powerSync = powerSync
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self.query = query
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}
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/// Performs a `PowerSyncDatabaseProtocol.getAll` to execute a SELECT query.
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/// A decoder users the provided `SqlCursor` to map the columns to the Structured Table type.
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@inlinable
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public func elements() async throws -> [Element] {
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let preparedQuery = query.prepareSqlite()
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return try await powerSync.getAll(
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sql: preparedQuery.sql,
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parameters: preparedQuery.bindings.map { try $0.powerSyncValue }
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) { psCursor in
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var decoder = PowerSyncQueryDecoder(cursor: psCursor)
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return try QueryValue(decoder: &decoder).queryOutput
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}
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}
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}
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/// The bindings provided by `prepare` seem to be wrapped in a Swift class
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/// which causes binding to fail. This converts values to be usable by the Kotlin SDK.
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extension QueryBinding {
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@inlinable
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var powerSyncValue: Sendable? {
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get throws {
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switch self {
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case let .blob(blob):
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return blob
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case let .date(date):
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let formatter = ISO8601DateFormatter()
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return formatter.string(from: date)
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case let .double(double):
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return double
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case let .int(int):
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return int
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case .null:
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return nil
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case let .text(text):
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return text
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case let .uuid(uuid):
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return uuid.uuidString
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case let .invalid(error):
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throw error
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}
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}
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}
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}

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