feat(tabs): track tab selecting history, create previousTab() method

src/components/tabs/tabs.ts

@@ -138,7 +138,7 @@ import {ViewController} from '../nav/view-controller';
     '</ion-navbar-section>' +
     '<ion-tabbar-section>' +
       '<tabbar role="tablist">' +
-        '<a *ngFor="let t of _tabs" [tab]="t" class="tab-button" [class.tab-disabled]="!t.enabled" [class.tab-hidden]="!t.show" role="tab" href="#">' +
+        '<a *ngFor="let t of _tabs" [tab]="t" class="tab-button" [class.tab-disabled]="!t.enabled" [class.tab-hidden]="!t.show" role="tab" href="#" (ionSelect)="select($event)">' +
           '<ion-icon *ngIf="t.tabIcon" [name]="t.tabIcon" [isActive]="t.isSelected" class="tab-button-icon"></ion-icon>' +
           '<span *ngIf="t.tabTitle" class="tab-button-text">{{t.tabTitle}}</span>' +
           '<ion-badge *ngIf="t.tabBadge" class="tab-badge" [ngClass]="\'badge-\' + t.tabBadgeStyle">{{t.tabBadge}}</ion-badge>' +
@@ -175,6 +175,11 @@ export class Tabs extends Ion {
    */
   navbarContainerRef: ViewContainerRef;
 
+  /**
+   * @private
+   */
+  selectHistory: string[] = [];
+
   /**
    * @private
    */
@@ -213,12 +218,7 @@ export class Tabs extends Ion {
   /**
    * @private
    */
-  @ViewChildren(TabButton) private _btns: any;
-
-  /**
-   * @private
-   */
-  parent: any;
+  parent: NavController;
 
   constructor(
     @Optional() parent: NavController,
@@ -271,12 +271,6 @@ export class Tabs extends Ion {
       });
     }
 
-    this._btns.toArray().forEach((tabButton: TabButton) => {
-      tabButton.ionSelect.subscribe((tab: Tab) => {
-        this.select(tab);
-      });
-    });
-
     let preloadTabs = (isBlank(this.preloadTabs) ? this._config.getBoolean('preloadTabs') : isTrueProperty(this.preloadTabs));
 
     // get the selected index
@@ -333,11 +327,11 @@ export class Tabs extends Ion {
   }
 
   /**
-   * @param {number} index Index of the tab you want to select
+   * @param {number|Tab} tabOrIndex Index, or the Tab instance, of the tab to select.
    */
-  select(tabOrIndex: any) {
-    let selectedTab = (typeof tabOrIndex === 'number' ? this.getByIndex(tabOrIndex) : tabOrIndex);
-    if (!selectedTab) {
+  select(tabOrIndex: number | Tab) {
+    let selectedTab: Tab = (typeof tabOrIndex === 'number' ? this.getByIndex(tabOrIndex) : tabOrIndex);
+    if (isBlank(selectedTab)) {
       return;
     }
 
@@ -390,9 +384,37 @@ export class Tabs extends Ion {
         this._onReady = null;
       }
 
+      // track the order of which tabs have been selected, by their index
+      // do not track if the tab index is the same as the previous
+      if (this.selectHistory[this.selectHistory.length - 1] !== selectedTab.id) {
+        this.selectHistory.push(selectedTab.id);
+      }
+
     });
   }
 
+  /**
+   * Get the previously selected Tab which is currently not disabled or hidden.
+   * @param {boolean} trimHistory If the selection history should be trimmed up to the previous tab selection or not.
+   * @returns {Tab}
+   */
+  previousTab(trimHistory: boolean = true): Tab {
+    // walk backwards through the tab selection history
+    // and find the first previous tab that is enabled and shown
+    console.log('run previousTab', this.selectHistory)
+    for (var i = this.selectHistory.length - 2; i >= 0; i--) {
+      var tab = this._tabs.find(t => t.id === this.selectHistory[i]);
+      if (tab && tab.enabled && tab.show) {
+        if (trimHistory) {
+          this.selectHistory.splice(i + 1);
+        }
+        return tab;
+      }
+    }
+
+    return null;
+  }
+
   /**
    * @param {number} index Index of the tab you want to get
    * @returns {Tab} Returns the tab who's index matches the one passed

src/components/tabs/test/tabs.spec.ts

@@ -0,0 +1,212 @@
+import {Component} from '@angular/core';
+import {App, Nav, Tabs, Tab, NavOptions, Config, ViewController, Platform} from '../../../../src';
+
+export function run() {
+
+describe('Tabs', () => {
+
+  describe('previousTab', () => {
+
+    it('should find the previous tab when there has been 3 selections', () => {
+      var tabs = mockTabs();
+      var tab0 = mockTab(tabs);
+      var tab1 = mockTab(tabs);
+      var tab2 = mockTab(tabs);
+      tabs.add(tab0);
+      tabs.add(tab1);
+      tabs.add(tab2);
+      tab0.root = SomePage;
+      tab1.root = SomePage;
+      tab2.root = SomePage;
+
+      tabs.select(tab0);
+      tabs.select(tab1);
+      tabs.select(tab2);
+
+      expect(tabs.selectHistory).toEqual([tab0.id, tab1.id, tab2.id]);
+
+      expect(tabs.previousTab(true)).toEqual(tab1);
+      expect(tabs.selectHistory).toEqual([tab0.id, tab1.id]);
+
+      expect(tabs.previousTab(true)).toEqual(tab0);
+      expect(tabs.selectHistory).toEqual([tab0.id]);
+    });
+
+    it('should not find a previous tab when there has only been one selection', () => {
+      var tabs = mockTabs();
+      var tab0 = mockTab(tabs);
+      var tab1 = mockTab(tabs);
+      tabs.add(tab0);
+      tabs.add(tab1);
+      tab0.root = SomePage;
+      tab1.root = SomePage;
+
+      tabs.select(tab0);
+
+      expect(tabs.previousTab(true)).toEqual(null);
+    });
+
+    it('should not find a previous tab when theres no history', () => {
+      var tabs = mockTabs();
+      expect(tabs.selectHistory.length).toEqual(0);
+      expect(tabs.previousTab(true)).toEqual(null);
+    });
+
+    it('should track tab selections', () => {
+      var tabs = mockTabs();
+      var tab0 = mockTab(tabs);
+      var tab1 = mockTab(tabs);
+      tabs.add(tab0);
+      tabs.add(tab1);
+      tab0.root = SomePage;
+      tab1.root = SomePage;
+
+      expect(tabs.selectHistory.length).toEqual(0);
+
+      tabs.select(tab0);
+      expect(tabs.selectHistory[0]).toEqual(tab0.id);
+      expect(tabs.selectHistory.length).toEqual(1);
+
+      tabs.select(tab1);
+      expect(tabs.selectHistory[0]).toEqual(tab0.id);
+      expect(tabs.selectHistory[1]).toEqual(tab1.id);
+      expect(tabs.selectHistory.length).toEqual(2);
+
+      tabs.select(tab0);
+      expect(tabs.selectHistory[0]).toEqual(tab0.id);
+      expect(tabs.selectHistory[1]).toEqual(tab1.id);
+      expect(tabs.selectHistory[2]).toEqual(tab0.id);
+      expect(tabs.selectHistory.length).toEqual(3);
+    });
+
+  });
+
+  describe('select', () => {
+
+    it('should select tab by tab instance', () => {
+      var tabs = mockTabs();
+      var tab0 = mockTab(tabs);
+      var tab1 = mockTab(tabs);
+      tabs.add(tab0);
+      tabs.add(tab1);
+
+      tab0.root = SomePage;
+      tab1.root = SomePage;
+
+      tabs.select(tab1);
+
+      expect(tab0.isSelected).toEqual(false);
+      expect(tab1.isSelected).toEqual(true);
+    });
+
+    it('should select tab by index', () => {
+      var tabs = mockTabs();
+      var tab0 = mockTab(tabs);
+      var tab1 = mockTab(tabs);
+      tabs.add(tab0);
+      tabs.add(tab1);
+
+      tab0.root = SomePage;
+      tab1.root = SomePage;
+
+      expect(tab0.isSelected).toBeUndefined();
+      expect(tab1.isSelected).toBeUndefined();
+
+      tabs.select(0);
+
+      expect(tab0.isSelected).toEqual(true);
+      expect(tab1.isSelected).toEqual(false);
+    });
+
+    it('should not select an invalid tab index', () => {
+      var tabs = mockTabs();
+      var tab0 = mockTab(tabs);
+      var tab1 = mockTab(tabs);
+      tabs.add(tab0);
+      tabs.add(tab1);
+
+      expect(tabs.select(22)).toBeUndefined();
+    });
+
+  });
+
+  describe('getByIndex', () => {
+
+    it('should get the tab', () => {
+      var tabs = mockTabs();
+      var tab0 = mockTab(tabs);
+      tab0.setRoot()
+      var tab1 = mockTab(tabs);
+      tabs.add(tab0);
+      tabs.add(tab1);
+
+      expect(tabs.getIndex(tab0)).toEqual(0);
+      expect(tabs.getIndex(tab1)).toEqual(1);
+    });
+
+  });
+
+  describe('getSelected', () => {
+
+    it('should get the selected tab', () => {
+      var tabs = mockTabs();
+      var tab0 = mockTab(tabs);
+      var tab1 = mockTab(tabs);
+      tabs.add(tab0);
+      tabs.add(tab1);
+
+      tab1.setSelected(true);
+
+      expect(tabs.getSelected()).toEqual(tab1);
+    });
+
+    it('should get null if no selected tab', () => {
+      var tabs = mockTabs();
+      var tab0 = mockTab(tabs);
+      var tab1 = mockTab(tabs);
+      tabs.add(tab0);
+      tabs.add(tab1);
+
+      expect(tabs.getSelected()).toEqual(null);
+    });
+
+  });
+
+  var app: App;
+  var config: Config;
+  var platform: Platform;
+  var _cd: any;
+
+  function mockNav(): Nav {
+    return new Nav(null, null, null, config, null, null, null, null, null);
+  }
+
+  function mockTabs(): Tabs {
+    return new Tabs(null, null, null, config, null, null, null);
+  }
+
+  function mockTab(parentTabs: Tabs): Tab {
+    var tab = new Tab(parentTabs, app, config, null, null, null, null, null, _cd);
+    tab.load = function(opts: any, cb: Function) {
+      cb();
+    };
+    return tab;
+  }
+
+  @Component({})
+  class SomePage {}
+
+  beforeEach(() => {
+    config = new Config();
+    platform = new Platform();
+    app = new App(config, null, platform);
+    _cd = {
+      reattach: function(){},
+      detach: function(){}
+    };
+  });
+
+});
+
+
+}