feat(ios-bottom-navigation): create tab bar from image nad label

Implements NativeScript/nativescript-angular#1893 for iOS.

Author: vchimev

Diff for: tns-core-modules/ui/bottom-navigation/bottom-navigation.ios.ts

@@ -399,21 +399,15 @@ export class BottomNavigation extends TabNavigationBase {
         items.forEach((item, i) => {
             const controller = this.getViewController(item);
 
-            let icon = null;
-            let title = "";
-
             if (this.tabStrip && this.tabStrip.items && this.tabStrip.items[i]) {
-                const tabStripItem = <TabStripItem>this.tabStrip.items[i];
-                icon = this._getIcon(tabStripItem.iconSource);
-                title = tabStripItem.title;
-
-                const tabBarItem = UITabBarItem.alloc().initWithTitleImageTag((title || ""), icon, i);
-                updateTitleAndIconPositions(tabStripItem, tabBarItem, controller);
+                const item = <TabStripItem>this.tabStrip.items[i];
+                const tabBarItem = this.createTabBarItem(item, i);
+                updateTitleAndIconPositions(item, tabBarItem, controller);
 
                 applyStatesToItem(tabBarItem, states);
 
                 controller.tabBarItem = tabBarItem;
-                tabStripItem.setNativeView(tabBarItem);
+                item.setNativeView(tabBarItem);
             }
 
             controllers.addObject(controller);
@@ -426,6 +420,20 @@ export class BottomNavigation extends TabNavigationBase {
         this._ios.moreNavigationController.delegate = this._moreNavigationControllerDelegate;
     }
 
+    private createTabBarItem(item: TabStripItem, index: number): UITabBarItem {
+        let image: UIImage;
+        let title: string;
+
+        // Image and Label children of TabStripItem
+        // take priority over its `iconSource` and `title` properties
+        image = item.image ? this._getIcon(item.image.src) : this._getIcon(item.iconSource);
+        title = item.label ? item.label.text : item.title;
+
+        const tabBarItem = UITabBarItem.alloc().initWithTitleImageTag(title, image, index);
+
+        return tabBarItem;
+    }
+
     private _getIconRenderingMode(): UIImageRenderingMode {
         return UIImageRenderingMode.AlwaysOriginal;
     }
@@ -523,4 +531,4 @@ function getTitleAttributesForStates(tabView: BottomNavigation): TabStates {
 function applyStatesToItem(item: UITabBarItem, states: TabStates) {
     item.setTitleTextAttributesForState(states.normalState, UIControlState.Normal);
     item.setTitleTextAttributesForState(states.selectedState, UIControlState.Selected);
-}
+}