Call callbacks from the last context only

timvermeulen · Nov 10, 2018 · 5152cf8 · 5152cf8
1 parent a67585b
commit 5152cf8
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Showing 10 changed files with 60 additions and 58 deletions.
diff --git a/Promise.xcodeproj/project.pbxproj b/Promise.xcodeproj/project.pbxproj
@@ -21,12 +21,12 @@
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 /* Begin PBXBuildFile section */
+		220A88DA21978534008FEB45 /* DispatchQueue+ExecutionContext.swift in Sources */ = {isa = PBXBuildFile; fileRef = 220A88D921978534008FEB45 /* DispatchQueue+ExecutionContext.swift */; };
 		OBJ_47 /* Atomic.swift in Sources */ = {isa = PBXBuildFile; fileRef = OBJ_9 /* Atomic.swift */; };
 		OBJ_48 /* BasicFuture+Foundation.swift in Sources */ = {isa = PBXBuildFile; fileRef = OBJ_11 /* BasicFuture+Foundation.swift */; };
 		OBJ_49 /* BasicFuture+Extras.swift in Sources */ = {isa = PBXBuildFile; fileRef = OBJ_12 /* BasicFuture+Extras.swift */; };
 		OBJ_50 /* BasicFuture.swift in Sources */ = {isa = PBXBuildFile; fileRef = OBJ_13 /* BasicFuture.swift */; };
 		OBJ_51 /* BasicPromise.swift in Sources */ = {isa = PBXBuildFile; fileRef = OBJ_14 /* BasicPromise.swift */; };
-		OBJ_52 /* DispatchQueue+ExecutionContext.swift in Sources */ = {isa = PBXBuildFile; fileRef = OBJ_15 /* DispatchQueue+ExecutionContext.swift */; };
 		OBJ_53 /* ExecutionContext.swift in Sources */ = {isa = PBXBuildFile; fileRef = OBJ_16 /* ExecutionContext.swift */; };
 		OBJ_54 /* Future+Foundation.swift in Sources */ = {isa = PBXBuildFile; fileRef = OBJ_18 /* Future+Foundation.swift */; };
 		OBJ_55 /* Future+Extras.swift in Sources */ = {isa = PBXBuildFile; fileRef = OBJ_19 /* Future+Extras.swift */; };
@@ -69,11 +69,11 @@
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 /* Begin PBXFileReference section */
+		220A88D921978534008FEB45 /* DispatchQueue+ExecutionContext.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = "DispatchQueue+ExecutionContext.swift"; sourceTree = "<group>"; };
 		OBJ_11 /* BasicFuture+Foundation.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "BasicFuture+Foundation.swift"; sourceTree = "<group>"; };
 		OBJ_12 /* BasicFuture+Extras.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "BasicFuture+Extras.swift"; sourceTree = "<group>"; };
 		OBJ_13 /* BasicFuture.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = BasicFuture.swift; sourceTree = "<group>"; };
 		OBJ_14 /* BasicPromise.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = BasicPromise.swift; sourceTree = "<group>"; };
-		OBJ_15 /* DispatchQueue+ExecutionContext.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "DispatchQueue+ExecutionContext.swift"; sourceTree = "<group>"; };
 		OBJ_16 /* ExecutionContext.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ExecutionContext.swift; sourceTree = "<group>"; };
 		OBJ_18 /* Future+Foundation.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "Future+Foundation.swift"; sourceTree = "<group>"; };
 		OBJ_19 /* Future+Extras.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "Future+Extras.swift"; sourceTree = "<group>"; };
@@ -123,8 +123,8 @@
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 			children = (
 				OBJ_9 /* Atomic.swift */,
-				OBJ_15 /* DispatchQueue+ExecutionContext.swift */,
 				OBJ_16 /* ExecutionContext.swift */,
+				220A88D921978534008FEB45 /* DispatchQueue+ExecutionContext.swift */,
 				OBJ_22 /* Result.swift */,
 				OBJ_23 /* Traversable.swift */,
 			);
@@ -312,11 +312,11 @@
 			buildActionMask = 0;
 			files = (
 				OBJ_47 /* Atomic.swift in Sources */,
+				220A88DA21978534008FEB45 /* DispatchQueue+ExecutionContext.swift in Sources */,
 				OBJ_48 /* BasicFuture+Foundation.swift in Sources */,
 				OBJ_49 /* BasicFuture+Extras.swift in Sources */,
 				OBJ_50 /* BasicFuture.swift in Sources */,
 				OBJ_51 /* BasicPromise.swift in Sources */,
-				OBJ_52 /* DispatchQueue+ExecutionContext.swift in Sources */,
 				OBJ_53 /* ExecutionContext.swift in Sources */,
 				OBJ_54 /* Future+Foundation.swift in Sources */,
 				OBJ_55 /* Future+Extras.swift in Sources */,

diff --git a/Sources/Promise/BasicFuture/BasicFuture.swift b/Sources/Promise/BasicFuture/BasicFuture.swift
@@ -9,29 +9,59 @@ public final class BasicFuture<Value> {
 }
 
 private extension BasicFuture {
+    struct Callback {
+        let changesContext: Bool
+        let callback: (Value) -> Void
+
+        func call(with value: Value, on context: ExecutionContext) {
+            if changesContext {
+                callback(value)
+            } else {
+                context { [callback] in callback(value) }
+            }
+        }
+    }
+
     enum State {
-        case pending(callbacks: [(Value) -> Void])
+        case pending(callbacks: [Callback])
         case fulfilled(with: Value)
     }
 
     convenience init(context: @escaping ExecutionContext, _ process: (BasicPromise<Value>) -> Void) {
         self.init(context: context)
         process(BasicPromise(future: self))
     }
+
+    func addCallback(_ callback: Callback) {
+        let value = state.access { state -> Value? in
+            switch state {
+            case .pending(var callbacks):
+                state = .pending(callbacks: [])
+                callbacks.append(callback)
+                state = .pending(callbacks: callbacks)
+                return nil
+
+            case .fulfilled(let value):
+                return value
+            }
+        }
+
+        if let value = value {
+            callback.call(with: value, on: context)
+        }
+    }
 }
 
 internal extension BasicFuture {
     func fulfill(with value: Value) {
-        let callbacks: [(Value) -> Void]? = state.access { state in
+        let callbacks: [Callback]? = state.access { state in
             guard case .pending(let callbacks) = state else { return nil }
 
             state = .fulfilled(with: value)
             return callbacks
         }
 
-        callbacks?.forEach { callback in
-            context { callback(value) }
-        }
+        callbacks?.forEach { $0.call(with: value, on: context) }
     }
 
     var testableValue: Value? {
@@ -56,29 +86,13 @@ public extension BasicFuture {
 
     @discardableResult
     func then(_ callback: @escaping (Value) -> Void) -> BasicFuture {
-        let value = state.access { state -> Value? in
-            switch state {
-            case .pending(var callbacks):
-                state = .pending(callbacks: [])
-                callbacks.append(callback)
-                state = .pending(callbacks: callbacks)
-                return nil
-
-            case .fulfilled(let value):
-                return value
-            }
-        }
-
-        if let value = value {
-            context { callback(value) }
-        }
-
+        addCallback(Callback(changesContext: false, callback: callback))
         return self
     }
 
     func changeContext(_ context: @escaping ExecutionContext) -> BasicFuture {
         return BasicFuture(context: context) { promise in
-            then(promise.fulfill)
+            addCallback(Callback(changesContext: true, callback: promise.fulfill))
         }
     }
 }
diff --git a/Sources/Promise/BasicFuture/BasicPromise.swift b/Sources/Promise/BasicFuture/BasicPromise.swift
@@ -1,7 +1,7 @@
 public final class BasicPromise<Value> {
-    let future: BasicFuture<Value>
+    internal let future: BasicFuture<Value>
 
-    init(future: BasicFuture<Value>) {
+    internal init(future: BasicFuture<Value>) {
         self.future = future
     }
 }

diff --git a/Sources/Promise/Future/Future+Extras.swift b/Sources/Promise/Future/Future+Extras.swift
@@ -210,11 +210,7 @@ public extension Collection {
 }
 
 public extension Future {
-    private func _always(_ handler: @escaping () -> Void) {
-        always(handler)
-    }
-
     func waiting<T>(for other: Future<T>) -> Future {
-        return async(other._always)
+        return async { other.always($0) }
     }
 }
diff --git a/Sources/Promise/Future/Future+Foundation.swift b/Sources/Promise/Future/Future+Foundation.swift
@@ -16,9 +16,7 @@ public extension Future {
     }
 
     func on(_ queue: DispatchQueue) -> Future {
-        return changeContext { resolve in
-            queue.async(execute: resolve)
-        }
+        return changeContext(queue.asyncContext)
     }
 
     func asyncAfter(deadline: DispatchTime, on queue: DispatchQueue) -> Future {

diff --git a/Sources/Promise/Future/Future.swift b/Sources/Promise/Future/Future.swift
@@ -1,24 +1,11 @@
 public final class Future<Value> {
     private let result: BasicFuture<Result<Value>>
 
-    init(result: BasicFuture<Result<Value>>) {
+    internal init(result: BasicFuture<Result<Value>>) {
         self.result = result
     }
 }
 
-private extension Future {
-    convenience init(
-        context: @escaping ExecutionContext,
-        _ process: (Promise<Value>) throws -> Void
-    ) {
-        let result = BasicPromise<Result<Value>>(future: .pending)
-        self.init(result: result.future.changeContext(context))
-
-        let promise = Promise(result: result)
-        promise.do { try process(promise) }
-    }
-}
-
 internal extension Future {
     var testableResult: Result<Value>? {
         return result.testableValue
@@ -82,8 +69,6 @@ public extension Future {
     }
 
     func changeContext(_ context: @escaping ExecutionContext) -> Future {
-        return Future(context: context) { promise in
-            promise.observe(self)
-        }
+        return .init(result: result.changeContext(context))
     }
 }
diff --git a/Sources/Promise/Future/Promise.swift b/Sources/Promise/Future/Promise.swift
@@ -1,7 +1,7 @@
 public final class Promise<Value> {
     private let result: BasicPromise<Result<Value>>
 
-    init(result: BasicPromise<Result<Value>>) {
+    internal init(result: BasicPromise<Result<Value>>) {
         self.result = result
     }
 }

diff --git a/Sources/Promise/Miscellaneous/ExecutionContext.swift b/Sources/Promise/Miscellaneous/ExecutionContext.swift
@@ -2,4 +2,4 @@ import Foundation
 
 public typealias ExecutionContext = (@escaping () -> Void) -> Void
 
-internal let defaultExecutionContext: ExecutionContext = { DispatchQueue.main.async(execute: $0) }
+internal let defaultExecutionContext = DispatchQueue.main.asyncContext
diff --git a/Tests/PromiseTests/PromiseRecoverTests.swift b/Tests/PromiseTests/PromiseRecoverTests.swift
@@ -4,13 +4,13 @@ import Promise
 final class PromiseRecoverTests: XCTestCase {
     func testRecover() {
         let future = Future<Void>.rejected(with: SimpleError()).delayed(by: 0.1)
-        let recovered = future.mapError { _ in () }
+        let recovered = future.mapError { _ in }
         assertWillBeFulfilled(recovered)
     }
 
     func testRecoverInstant() {
         let future = Future<Void>.rejected(with: SimpleError())
-        let recovered = future.mapError { _ in () }
+        let recovered = future.mapError { _ in }
         assertWillBeFulfilled(recovered)
     }
 

diff --git a/Tests/PromiseTests/PromiseTests.swift b/Tests/PromiseTests/PromiseTests.swift
@@ -114,4 +114,13 @@ final class PromiseTests: XCTestCase {
         called = true
         wait()
     }
+
+    func testContextChange() {
+        let future = Future.fulfilled
+            .changeContext { _ in XCTFail() }
+            .changeContext { $0() }
+            .map {}
+
+        assertIsFulfilled(future)
+    }
 }