Add postTransitionBehavior to ContainerViewController

CHANGELOG.md

@@ -4,7 +4,11 @@
 
 * Make it possible to override functions in container, which aid in `ManagedChild` managemet.
 [Will McGinty](https://github.com/willmcginty)
-[#87](https://github.com/BottleRocketStudios/iOS-UtiliKit/pull/82)
+[#87](https://github.com/BottleRocketStudios/iOS-UtiliKit/pull/87)
+
+* Add `postTransitionBehavior` to `ContainerViewController`, automating some common child management scenarios
+[Dimitar Milinski](https://github.com/dmilinski)
+[#88](https://github.com/BottleRocketStudios/iOS-UtiliKit/pull/88)
 
 ##### Bug Fixes
 

Sources/UtiliKit/Container/ContainerViewController.swift

@@ -9,6 +9,14 @@ import UIKit
 
 open class ContainerViewController: UIViewController {
 
+    // MARK: Subtypes
+    public enum PostTransitionBehavior {
+        case removeAllNonVisibleChildrenExcept([AnyHashable])
+        case none
+
+        static var removeAllNonVisibleChildren: PostTransitionBehavior { return .removeAllNonVisibleChildrenExcept([]) }
+    }
+
     //MARK: Properties
     open var managedChildren: [ManagedChild] = []
     open var visibleIndex: Int? { return visibleController.flatMap(index(ofChild:)) }
@@ -26,6 +34,7 @@ open class ContainerViewController: UIViewController {
     // MARK: Transitioning
     private var containerTransitionContext: UIViewControllerContextTransitioning?
     open var containerTransitionCoordinator: ContainerViewControllerTransitionCoordinator?
+    open var postTransitionBehavior: PostTransitionBehavior = .none
 
     //MARK: Initializers
     public convenience init(managedChildren: [ManagedChild], delegate: ContainerViewControllerDelegate? = nil) {
@@ -162,7 +171,22 @@ private extension ContainerViewController {
             visibleController = source
         }
 
+        switch postTransitionBehavior {
+        case .removeAllNonVisibleChildrenExcept(let identifiers):
+            removeAllNonVisibleChildren(except: identifiers)
+        case .none:
+            break
+        }
+
         containerTransitionContext = nil
         isTransitioning = false
     }
+
+    func removeAllNonVisibleChildren(except identifiers: [AnyHashable]) {
+        managedChildren.forEach {
+            if $0.viewController != visibleChild?.viewController && !identifiers.contains($0.identifier) {
+                removeChild($0)
+            }
+        }
+    }
 }

Tests/ContainerTests.swift

@@ -60,4 +60,54 @@ class ContainerTests: XCTestCase {
 
         XCTAssertNil(container.child(at: children.count))
     }
+
+    func test_Container_removeNonVisbleChildren() {
+        let children = [Child(identifier: "title", viewController: UIViewController()),
+                        Child(identifier: "title2", viewController: UIViewController()),
+                        Child(identifier: "title3", viewController: UIViewController()),
+                        Child(identifier: "title4", viewController: UIViewController())]
+
+        let container = ContainerViewController(managedChildren: children)
+        container.loadViewIfNeeded()
+        container.postTransitionBehavior = .removeAllNonVisibleChildren
+
+        let transition = expectation(description: "waitForTransition")
+
+        container.transitionToControllerForChild(withIdentifier: "title3") { (_) in
+            transition.fulfill()
+        }
+
+        waitForExpectations(timeout: 1.0) { (_) in
+            XCTAssert(container.managedChildren.count == 1)
+            XCTAssert((container.managedChildren.first?.identifier as? String) == "title3")
+        }
+    }
+
+    func test_Container_removeNonVisbleChildrenExcept() {
+        let children = [Child(identifier: "title", viewController: UIViewController()),
+                        Child(identifier: "title2", viewController: UIViewController()),
+                        Child(identifier: "title3", viewController: UIViewController()),
+                        Child(identifier: "title4", viewController: UIViewController())]
+
+        let container = ContainerViewController(managedChildren: children)
+        container.loadViewIfNeeded()
+        container.postTransitionBehavior = .removeAllNonVisibleChildrenExcept(["title2", "title4"])
+
+        let transition = expectation(description: "waitForTransition")
+
+        container.transitionToControllerForChild(withIdentifier: "title3") { (_) in
+            transition.fulfill()
+        }
+
+        waitForExpectations(timeout: 1.0) { (_) in
+            XCTAssert(container.managedChildren.count == 3)
+            let identifiers: [String] = container.managedChildren.compactMap {
+                return $0.identifier as? String
+            }
+
+            XCTAssert(identifiers.contains("title2"))
+            XCTAssert(identifiers.contains("title4"))
+            XCTAssert(identifiers.contains("title3"))
+        }
+    }
 }