Merge pull request #4 from trafi/feature/destination

add destination in ImplicitFlow

StoryFlow/Flow/ImplicitFlow/ImplicitFlow.swift

@@ -1,6 +1,31 @@
 import Foundation
 import UIKit
 
+extension Flow {
+
+    /**
+     Returns view controller by matching type of provided `value`
+
+     See [tests examples](https://github.com/trafi/StoryFlow/blob/master/StoryFlowTests/ImplicitFlowTests.swift).
+
+     - Parameter value: The value being passed to next view controller.
+     */
+    public static func destination(for value: Value) -> UIViewController? {
+        return destination(for: (value, Value.self))
+    }
+
+    private static func destination(for output: ValueAndType) -> UIViewController? {
+        let (value, type) = OutputTransform.apply(output)
+
+        for inType in inputRequiringTypes where oneOf(inType._inputType, contains: type) {
+            return inType._create(input: value)
+        }
+
+        return nil
+    }
+
+}
+
 extension Flow {
 
     public static func implicit() -> Flow {
@@ -24,9 +49,8 @@ extension Flow {
             }
 
             // MARK: Input
-
-            for inType in inputRequiringTypes where oneOf(inType._inputType, contains: type) {
-                let to = inType._create(input: value)
+
+            if let to = Flow<Any>.destination(for: output) {
                 let transition = TransitionInfo(from: from, producedType: output.type, receivedType: type, to: to, isUnwind: false)
                 if CustomTransition.attempt(transition) == false {
                     from.show(to, sender: nil)

StoryFlowTests/ImplicitFlowTests.swift

@@ -2,6 +2,41 @@ import XCTest
 import StoryFlow
 
 class ImplicitFlowTests: XCTestCase {
+
+    // MARK: Destination
+
+    func testDestination_itReturnsNilWhenNoVcFound() {
+
+        // Arrange
+        class T {}
+
+        let output = T()
+
+        // Act
+        let destination = Flow<T>.destination(for: output)
+
+        // Assert
+        XCTAssert(destination == nil)
+    }
+
+
+    func testDestination_itReturnsVcWithInput() {
+
+        // Arrange
+        class T {}
+
+        class To: UIViewController, InputRequiring { typealias InputType = T }
+
+        let output = T()
+
+        // Act
+        let destination = Flow<T>.destination(for: output)
+
+        // Assert
+        XCTAssert(destination is To)
+        XCTAssert((destination as! To).input === output)
+    }
+
 
     // MARK: Show
 
@@ -483,6 +518,29 @@ class ImplicitFlowTests: XCTestCase {
     }
 
     // MARK: Output transforms
+
+    func testDestination_itReturnsNextVcByTransformedOutput() {
+
+        // Arrange
+        class T1 {}
+        class T2 {}
+
+        class To: UIViewController, InputRequiring { typealias InputType = T2 }
+
+        let transformedOutput = T2()
+
+        OutputTransform.register { (_: T1) in transformedOutput }
+
+        // Act
+        let destination = Flow.destination(for: T1())
+
+        // Assert
+        XCTAssert(destination is To)
+        XCTAssert((destination as! To).input === transformedOutput)
+
+        // Clean up
+        OutputTransform.reset()
+    }
 
     func testProduce_itShowsNextVcByTransformedOutput() {