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April 16, 2025 20:01
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| import SwiftUI | |
| import Combine | |
| // MARK: - The Handler | |
| final class DebounceHandler<V: Equatable, S: Scheduler>: ObservableObject { | |
| private let debounceTime: S.SchedulerTimeType.Stride | |
| private let scheduler: S | |
| private let action: (V, V) -> Void | |
| private var previousValue: V | |
| private var currentValue: V | |
| private var cancellable: AnyCancellable? | |
| init( | |
| initialValue: V, | |
| debounceTime: S.SchedulerTimeType.Stride, | |
| scheduler: S = RunLoop.main, | |
| action: @escaping (V, V) -> Void | |
| ) { | |
| self.previousValue = initialValue | |
| self.currentValue = initialValue | |
| self.debounceTime = debounceTime | |
| self.scheduler = scheduler | |
| self.action = action | |
| } | |
| func updateValue(oldValue: V? = nil, newValue: V) { | |
| cancellable?.cancel() | |
| cancellable = Just((oldValue ?? previousValue, newValue)) | |
| .delay(for: debounceTime, scheduler: scheduler) | |
| .sink { [weak self] pair in | |
| self?.action(pair.0, pair.1) | |
| } | |
| } | |
| } | |
| // MARK: - The Modifer | |
| fileprivate struct DebounceModifier<V: Equatable, S: Scheduler>: ViewModifier { | |
| let value: V | |
| let debounceTime: S.SchedulerTimeType.Stride | |
| let scheduler: S | |
| let action: (V, V) -> Void | |
| @StateObject private var handler: DebounceHandler<V, S> | |
| init(value: V, debounceTime: S.SchedulerTimeType.Stride, scheduler: S, action: @escaping (V, V) -> Void) { | |
| self.value = value | |
| self.debounceTime = debounceTime | |
| self.scheduler = scheduler | |
| self.action = action | |
| _handler = StateObject(wrappedValue: DebounceHandler(initialValue: value, debounceTime: debounceTime, scheduler: scheduler, action: action)) | |
| } | |
| func body(content: Content) -> some View { | |
| content | |
| .onChange(of: value, handler.updateValue(oldValue:newValue:)) | |
| } | |
| } | |
| // Mark: View Using ⬇ | |
| public extension View { | |
| func onChange<V, S>( | |
| of value: V, | |
| debounce: S.SchedulerTimeType.Stride, | |
| scheduler: S = RunLoop.main, | |
| _ action: @escaping (V, V) -> Void | |
| ) -> some View where V: Equatable, S: Scheduler { | |
| modifier(DebounceModifier(value: value, debounceTime: debounce, scheduler: scheduler, action: action)) | |
| } | |
| } | |
| //MARK: - Unit On Handler | |
| @testable import <#Module#> | |
| import XCTest | |
| final class DebounceHandlerTests: XCTestCase { | |
| func testDebouncedValueTriggersOnce() { | |
| let expectation = self.expectation(description: "debounced action triggered") | |
| var received: (Int, Int)? | |
| let handler = DebounceHandler( | |
| initialValue: 0, | |
| debounceTime: .milliseconds(200), | |
| action: { old, new in | |
| received = (old, new) | |
| expectation.fulfill() | |
| } | |
| ) | |
| let updates = (0...10) | |
| updates.forEach { | |
| handler.updateValue(newValue: $0) | |
| } | |
| wait(for: [expectation], timeout: 1.0) | |
| XCTAssertEqual(received?.0, 0) | |
| XCTAssertEqual(received?.1, 10) | |
| } | |
| func testDebouncedValueTriggersMultipleTimes() { | |
| let expectation = self.expectation(description: "debounced action triggered") | |
| var received: (Int, Int)? | |
| let handler = DebounceHandler( | |
| initialValue: 0, | |
| debounceTime: .milliseconds(200), | |
| action: { old, new in | |
| received = (old, new) | |
| expectation.fulfill() | |
| } | |
| ) | |
| let updates = [0, 2, 5, 10] | |
| updates.enumerated().forEach { index, current in | |
| let previous = index == 0 ? 0 : updates[index - 1] | |
| let delay = DispatchTime.now() + .milliseconds(50 * index) | |
| DispatchQueue.main.asyncAfter(deadline: delay) { | |
| handler.updateValue(oldValue: previous, newValue: current) | |
| } | |
| } | |
| wait(for: [expectation], timeout: 2.0) | |
| XCTAssertEqual(received?.0, 5) | |
| XCTAssertEqual(received?.1, 10) | |
| } | |
| } | |
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