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Box @Fetch* property wrappers in SwiftUI state when possible #486

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64a1b69
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stephencelis Jul 6, 2026
558526c
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stephencelis Jul 7, 2026
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54 changes: 47 additions & 7 deletions Sources/SQLiteData/Fetch.swift
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Original file line number Diff line number Diff line change
@@ -1,7 +1,6 @@
public import GRDB
public import Sharing
import StructuredQueriesCore
public import Sharing

#if canImport(Combine)
public import Combine
Expand All @@ -22,11 +21,32 @@ public import Sharing
@dynamicMemberLookup
@propertyWrapper
public struct Fetch<Value: Sendable>: Sendable {
/// The underlying shared reader powering the property wrapper.
///
/// Shared readers come from the [Sharing](https://github.com/pointfreeco/swift-sharing) package,
/// a general solution to observing and persisting changes to external data sources.
public var sharedReader: SharedReader<Value>
#if canImport(SwiftUI)
/// The underlying shared reader powering the property wrapper.
///
/// Shared readers come from the [Sharing](https://github.com/pointfreeco/swift-sharing)
/// package, a general solution to observing and persisting changes to external data sources.
public private(set) var sharedReader: SharedReader<Value> {
@storageRestrictions(initializes: box, state)
init(initialValue) {
let box = FetchBox(sharedReader: initialValue)
self.box = box
state = SwiftUI.State(wrappedValue: box)
}
get { state.wrappedValue.sharedReader }
nonmutating set { state.wrappedValue.sharedReader = newValue }
}

private let box: FetchBox<Value>
private let state: SwiftUI.State<FetchBox<Value>>
private let generation = SwiftUI.State(wrappedValue: 0)
#else
/// The underlying shared reader powering the property wrapper.
///
/// Shared readers come from the [Sharing](https://github.com/pointfreeco/swift-sharing)
/// package, a general solution to observing and persisting changes to external data sources.
public private(set) var sharedReader: SharedReader<Value>
#endif

/// Data associated with the underlying query.
public var wrappedValue: Value {
Expand Down Expand Up @@ -93,6 +113,7 @@ public struct Fetch<Value: Sendable>: Sendable {
database: (any DatabaseReader)? = nil
) {
sharedReader = SharedReader(wrappedValue: wrappedValue, .fetch(request, database: database))
setFetchKeyID(for: request, database: database, scheduler: nil)
}

/// Replaces the wrapped value with data from the given request.
Expand All @@ -110,6 +131,19 @@ public struct Fetch<Value: Sendable>: Sendable {
try await sharedReader.load(.fetch(request, database: database))
return FetchSubscription(sharedReader: sharedReader)
}

#if !canImport(SwiftUI)
@_transparent
#endif
private func setFetchKeyID<V: Sendable>(
for request: some FetchKeyRequest<V>,
database: (any DatabaseReader)?,
scheduler: (any ValueObservationScheduler & Hashable)?
) {
#if canImport(SwiftUI)
box.fetchKeyID = FetchKey(request: request, database: database, scheduler: scheduler).id
#endif
}
}

extension Fetch {
Expand All @@ -132,6 +166,7 @@ extension Fetch {
wrappedValue: wrappedValue,
.fetch(request, database: database, scheduler: scheduler)
)
setFetchKeyID(for: request, database: database, scheduler: scheduler)
}

/// Replaces the wrapped value with data from the given request.
Expand Down Expand Up @@ -169,7 +204,11 @@ extension Fetch: Equatable where Value: Equatable {
#if canImport(SwiftUI)
extension Fetch: DynamicProperty {
public func update() {
sharedReader.update()
let persisted = state.wrappedValue
if persisted !== box {
persisted.reconcile(from: box, propertyName: "@Fetch")
}
persisted.subscribe(generation: generation)
}

/// Initializes this property with a request associated with the wrapped value.
Expand All @@ -192,6 +231,7 @@ extension Fetch: Equatable where Value: Equatable {
wrappedValue: wrappedValue,
.fetch(request, database: database, animation: animation)
)
setFetchKeyID(for: request, database: database, scheduler: .animation(animation))
}

/// Replaces the wrapped value with data from the given request.
Expand Down
97 changes: 70 additions & 27 deletions Sources/SQLiteData/FetchAll.swift
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,7 +1,6 @@
public import GRDB
public import Sharing
public import StructuredQueriesCore
public import Sharing

#if canImport(Combine)
public import Combine
Expand All @@ -22,11 +21,32 @@ public import Sharing
@dynamicMemberLookup
@propertyWrapper
public struct FetchAll<Element: Sendable>: Sendable {
/// The underlying shared reader powering the property wrapper.
///
/// Shared readers come from the [Sharing](https://github.com/pointfreeco/swift-sharing) package,
/// a general solution to observing and persisting changes to external data sources.
public var sharedReader: SharedReader<[Element]> = SharedReader(value: [])
#if canImport(SwiftUI)
/// The underlying shared reader powering the property wrapper.
///
/// Shared readers come from the [Sharing](https://github.com/pointfreeco/swift-sharing)
/// package, a general solution to observing and persisting changes to external data sources.
public private(set) var sharedReader: SharedReader<[Element]> {
@storageRestrictions(initializes: box, state)
init(initialValue) {
let box = FetchBox(sharedReader: initialValue)
self.box = box
state = SwiftUI.State(wrappedValue: box)
}
get { state.wrappedValue.sharedReader }
nonmutating set { state.wrappedValue.sharedReader = newValue }
}

private let box: FetchBox<[Element]>
private let state: SwiftUI.State<FetchBox<[Element]>>
private let generation = SwiftUI.State(wrappedValue: 0)
#else
/// The underlying shared reader powering the property wrapper.
///
/// Shared readers come from the [Sharing](https://github.com/pointfreeco/swift-sharing)
/// package, a general solution to observing and persisting changes to external data sources.
public private(set) var sharedReader: SharedReader<[Element]> = SharedReader(value: [])
#endif

/// A collection of data associated with the underlying query.
public var wrappedValue: [Element] {
Expand Down Expand Up @@ -139,13 +159,12 @@ public struct FetchAll<Element: Sendable>: Sendable {
Element == V.QueryOutput,
V.QueryOutput: Sendable
{
let request = FetchAllStatementValueRequest(statement: statement)
sharedReader = SharedReader(
wrappedValue: wrappedValue,
.fetch(
FetchAllStatementValueRequest(statement: statement),
database: database
)
.fetch(request, database: database)
)
setFetchKeyID(for: request, database: database, scheduler: nil)
}

/// Initializes this property with a query associated with the wrapped value.
Expand All @@ -164,13 +183,12 @@ public struct FetchAll<Element: Sendable>: Sendable {
Element: QueryRepresentable,
Element == S.QueryValue.QueryOutput
{
let request = FetchAllStatementValueRequest(statement: statement)
sharedReader = SharedReader(
wrappedValue: wrappedValue,
.fetch(
FetchAllStatementValueRequest(statement: statement),
database: database
)
.fetch(request, database: database)
)
setFetchKeyID(for: request, database: database, scheduler: nil)
}

/// Replaces the wrapped value with data from the given query.
Expand Down Expand Up @@ -219,10 +237,29 @@ public struct FetchAll<Element: Sendable>: Sendable {
)
return FetchSubscription(sharedReader: sharedReader)
}

#if !canImport(SwiftUI)
@_transparent
#endif
private func setFetchKeyID<V: Sendable>(
for request: some FetchKeyRequest<V>,
database: (any DatabaseReader)?,
scheduler: (any ValueObservationScheduler & Hashable)?
) {
#if canImport(SwiftUI)
box.fetchKeyID = FetchKey(request: request, database: database, scheduler: scheduler).id
#endif
}
}

extension FetchAll {
@available(*, deprecated, message: "Remove unused parameters: 'database', 'scheduler'.")
@available(
*,
deprecated,
message: """
'@Selection' type requires a query to be fetched; provide one or remove unused parameters: 'database', 'scheduler'.
"""
)
public init(
wrappedValue: [Element] = [],
database: (any DatabaseReader)? = nil,
Expand Down Expand Up @@ -294,14 +331,12 @@ extension FetchAll {
Element == V.QueryOutput,
V.QueryOutput: Sendable
{
let request = FetchAllStatementValueRequest(statement: statement)
sharedReader = SharedReader(
wrappedValue: wrappedValue,
.fetch(
FetchAllStatementValueRequest(statement: statement),
database: database,
scheduler: scheduler
)
.fetch(request, database: database, scheduler: scheduler)
)
setFetchKeyID(for: request, database: database, scheduler: scheduler)
}

/// Initializes this property with a query associated with the wrapped value.
Expand All @@ -323,14 +358,12 @@ extension FetchAll {
Element: QueryRepresentable,
Element == S.QueryValue.QueryOutput
{
let request = FetchAllStatementValueRequest(statement: statement)
sharedReader = SharedReader(
wrappedValue: wrappedValue,
.fetch(
FetchAllStatementValueRequest(statement: statement),
database: database,
scheduler: scheduler
)
.fetch(request, database: database, scheduler: scheduler)
)
setFetchKeyID(for: request, database: database, scheduler: scheduler)
}

/// Replaces the wrapped value with data from the given query.
Expand Down Expand Up @@ -403,10 +436,20 @@ extension FetchAll: Equatable where Element: Equatable {
#if canImport(SwiftUI)
extension FetchAll: DynamicProperty {
public func update() {
sharedReader.update()
let persisted = state.wrappedValue
if persisted !== box {
persisted.reconcile(from: box, propertyName: "@FetchAll")
}
persisted.subscribe(generation: generation)
}

@available(*, deprecated, message: "Remove unused parameters: 'database', 'animation'.")
@available(
*,
deprecated,
message: """
'@Selection' type requires a query to be fetched; provide one or remove unused parameters: 'database', 'scheduler'.
"""
)
public init(
wrappedValue: [Element] = [],
database: (any DatabaseReader)? = nil,
Expand Down
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