'Cancel' for PromiseKit -- provides the ability to cancel promises and promise chains

Author: dougzilla32

Cartfile

@@ -1 +1,2 @@
-github "mxcl/PromiseKit" ~> 6.0
+#github "mxcl/PromiseKit" ~> 6.0
+github "dougzilla32/PromiseKit" "CoreCancel"

Cartfile.resolved

@@ -1 +1 @@
-github "mxcl/PromiseKit" "6.3.4"
+github "dougzilla32/PromiseKit" "087b3cf470890ff9ea841212e2f3e285fecf3988"

Sources/HMAcessoryBrowser+Promise.swift

@@ -24,6 +24,7 @@ public class HMPromiseAccessoryBrowser {
 private class BrowserProxy: PromiseProxy<[HMAccessory]>, HMAccessoryBrowserDelegate {
     let browser = HMAccessoryBrowser()
     let scanInterval: ScanInterval
+    var timer: CancellablePromise<Void>?
 
     init(scanInterval: ScanInterval) {
         self.scanInterval = scanInterval
@@ -40,7 +41,7 @@ private class BrowserProxy: PromiseProxy<[HMAccessory]>, HMAccessoryBrowserDeleg
         }
 
         if let timeout = timeout {
-            after(seconds: timeout)
+            self.timer = cancellable(after(seconds: timeout))
             .done { [weak self] () -> Void in
                 guard let _self = self else { return }
                 _self.reject(HMPromiseAccessoryBrowserError.noAccessoryFound)
@@ -60,6 +61,7 @@ private class BrowserProxy: PromiseProxy<[HMAccessory]>, HMAccessoryBrowserDeleg
 
     override func cancel() {
         browser.stopSearchingForNewAccessories()
+        timer?.cancel()
         super.cancel()
     }
 
@@ -74,3 +76,11 @@ private class BrowserProxy: PromiseProxy<[HMAccessory]>, HMAccessoryBrowserDeleg
 }
 
 #endif
+
+//////////////////////////////////////////////////////////// Cancellable wrapper
+
+extension HMPromiseAccessoryBrowser {
+    public func cancellableStart(scanInterval: ScanInterval) -> CancellablePromise<[HMAccessory]> {
+        return cancellable(start(scanInterval: scanInterval))
+    }
+}

Sources/HMHomeManager+Promise.swift

@@ -43,18 +43,34 @@ extension HMHomeManager {
 internal class HMHomeManagerProxy: PromiseProxy<[HMHome]>, HMHomeManagerDelegate {
 
     fileprivate let manager: HMHomeManager
+    private var task: DispatchWorkItem!
 
     override init() {
         self.manager = HMHomeManager()
         super.init()
         self.manager.delegate = self
 
-        DispatchQueue.main.asyncAfter(deadline: .now() + 20.0) { [weak self] in
+        self.task = DispatchWorkItem { [weak self] in
             self?.reject(HomeKitError.permissionDeined)
         }
+        DispatchQueue.main.asyncAfter(deadline: .now() + 20.0, execute: self.task)
     }
 
     func homeManagerDidUpdateHomes(_ manager: HMHomeManager) {
         fulfill(manager.homes)
     }
+
+    override func cancel() {
+        self.task.cancel()
+        super.cancel()
+    }
+}
+
+//////////////////////////////////////////////////////////// Cancellable wrapper
+
+@available(iOS 8.0, tvOS 10.0, *)
+extension HMHomeManager {
+    public func cancellableHomes() -> CancellablePromise<[HMHome]> {
+        return cancellable(homes())
+    }
 }

Sources/Utils.swift

@@ -3,7 +3,9 @@ import PromiseKit
 /**
     Commonly used functionality when promisifying a delegate pattern
 */
-internal class PromiseProxy<T>: NSObject {
+internal class PromiseProxy<T>: NSObject, CancellableTask {
+    var isCancelled = false
+    
     internal let (promise, seal) = Promise<T>.pending();
 
     private var retainCycle: PromiseProxy?
@@ -13,7 +15,9 @@ internal class PromiseProxy<T>: NSObject {
         // Create a retain cycle
         self.retainCycle = self
         // And ensure we break it when the promise is resolved
-        _ = promise.ensure { self.retainCycle = nil }
+        _ = promise.ensure { self.retainCycle = nil ; self.promise.setCancellableTask(nil) }
+        
+        promise.setCancellableTask(self)
     }
 
     /// These functions ensure we only resolve the promise once
@@ -28,6 +32,7 @@ internal class PromiseProxy<T>: NSObject {
 
     /// Cancel helper
     internal func cancel() {
+        isCancelled = true
         self.reject(PMKError.cancelled)
     }
 }

Tests/HMAccessoryBrowserTests.swift

@@ -46,7 +46,7 @@ extension HMAccessoryBrowser {
     @objc func pmk_startSearchingForNewAccessories() {
         after(.milliseconds(100))
         .done { swag in
-            self.delegate!.accessoryBrowser?(self, didFindNewAccessory: MockAccessory())
+            self.delegate?.accessoryBrowser?(self, didFindNewAccessory: MockAccessory())
         }
     }
 }
@@ -81,4 +81,36 @@ func swizzle(_ foo: AnyClass, _ from: Selector, isClassMethod: Bool = false, bod
     method_exchangeImplementations(swizzledMethod, originalMethod)
 }
 
+//////////////////////////////////////////////////////////// Cancellation
+
+extension HMAccessoryBrowserTests {
+    
+    func testCancelBrowserScanReturningFirst() {
+        swizzle(HMAccessoryBrowser.self, #selector(HMAccessoryBrowser.startSearchingForNewAccessories)) {
+            let ex = expectation(description: "")
+            
+            cancellable(HMPromiseAccessoryBrowser().start(scanInterval: .returnFirst(timeout: 0.5)))
+            .done { accessories in
+                XCTAssertEqual(accessories.count, 1)
+                XCTFail()
+            }.catch(policy: .allErrors) {
+                $0.isCancelled ? ex.fulfill() : XCTFail()
+            }.cancel()
+            
+            waitForExpectations(timeout: 1, handler: nil)
+        }
+    }
+    
+    func testCancelBrowserScanReturningTimeout() {
+        let ex = expectation(description: "")
+        
+        cancellable(HMPromiseAccessoryBrowser().start(scanInterval: .returnFirst(timeout: 0.5)))
+        .catch(policy: .allErrors) {
+            $0.isCancelled ? ex.fulfill() : XCTFail()
+        }.cancel()
+        
+        waitForExpectations(timeout: 1, handler: nil)
+    }
+}
+
 #endif