Add popAndPush convenience method (fixes #110)

Sources/FlowStacks/Convenience methods/Array+convenienceMethods.swift

@@ -278,6 +278,18 @@ public extension Array where Element: RouteProtocol, Element.Screen: Identifiabl
   }
 }
 
+// MARK: - Pop and push
+
+public extension Array where Element: RouteProtocol {
+  /// Pops the top pushed screen and pushes a new screen, resulting in a push transition to the new screen.
+  /// Only the top screen will be popped, and it must have been pushed (not presented).
+  /// - Parameter screen: The new screen to push.
+  mutating func popAndPush(_ screen: Element.Screen) {
+    pop()
+    push(screen)
+  }
+}
+
 // MARK: - Dismiss
 
 public extension Array where Element: RouteProtocol {

Sources/FlowStacks/Convenience methods/FlowNavigator+convenienceMethods.swift

@@ -256,6 +256,17 @@ public extension FlowNavigator where Screen == AnyHashable {
   }
 }
 
+// MARK: - Pop and push
+
+public extension FlowNavigator {
+  /// Pops the top pushed screen and pushes a new screen, resulting in a push transition to the new screen.
+  /// Only the top screen will be popped, and it must have been pushed (not presented).
+  /// - Parameter screen: The new screen to push.
+  func popAndPush(_ screen: Screen) {
+    routes.popAndPush(screen)
+  }
+}
+
 // MARK: - Dismiss
 
 public extension FlowNavigator {

Sources/FlowStacks/Convenience methods/FlowPath+convenienceMethods.swift

@@ -180,6 +180,17 @@ public extension FlowPath {
   }
 }
 
+// MARK: - Pop and push
+
+public extension FlowPath {
+  /// Pops the top pushed screen and pushes a new screen, resulting in a push transition to the new screen.
+  /// Only the top screen will be popped, and it must have been pushed (not presented).
+  /// - Parameter screen: The new screen to push.
+  mutating func popAndPush(_ screen: AnyHashable) {
+    routes.popAndPush(screen)
+  }
+}
+
 // MARK: - Dismiss
 
 public extension FlowPath {

Tests/FlowStacksTests/ConvenienceMethodsTests.swift

@@ -86,6 +86,24 @@ final class ConvenienceMethodsTests: XCTestCase {
     XCTAssertEqual(path.count, 2)
   }
 
+  func testPopAndPush() {
+    var path = FlowPath([.push(1), .push("two"), .push(true)])
+    path.popAndPush("three")
+    XCTAssertEqual(path.count, 3)
+    // Last route should be a push of the new screen
+    XCTAssertEqual(path.routes.last?.style, .push)
+    XCTAssertEqual(path.routes.last?.screen as? String, "three")
+    // Previous screen should be unchanged
+    XCTAssertEqual(path.routes[1].screen as? String, "two")
+  }
+
+  func testPopAndPushFromSingleScreen() {
+    var path = FlowPath([.push(1)])
+    path.popAndPush("replacement")
+    XCTAssertEqual(path.count, 1)
+    XCTAssertEqual(path.routes.last?.screen as? String, "replacement")
+  }
+
   func testDismissAllWhereFirstIsPushed() {
     var path = FlowPath([.push(1), .sheet("two"), .push(3), .cover("four"), .push(5), .cover("six"), .push(7)])
     path.dismiss()