fix(tabs): adding tab content to DOM just if selected tab (#1422)

demo/src/app/components/+tabs/demos/dynamic-insert/dynamic-insert.html

@@ -0,0 +1,5 @@
+<tabset [dynamic]="true">
+  <tab heading="Title" id="tab1">Dynamic insert content</tab>
+  <tab heading="Title 1">Dynamic insert content 1</tab>
+  <tab heading="Title 2">Dynamic insert content 2</tab>
+</tabset>

demo/src/app/components/+tabs/demos/dynamic-insert/dynamic-insert.ts

@@ -0,0 +1,7 @@
+import { Component } from '@angular/core';
+
+@Component({
+  selector: 'demo-tabs-dynamic-insert',
+  templateUrl: './dynamic-insert.html'
+})
+export class DemoTabsDynamicInsertComponent {}

demo/src/app/components/+tabs/demos/index.ts

@@ -10,6 +10,7 @@ import { DemoTabsDisabledComponent } from './disabled/disabled';
 import { DemoTabsCustomComponent } from './custom-template/custom-template';
 import { DemoTabsSelectEventComponent } from './select-event/select-event';
 import { DemoAccessibilityComponent } from './accessibility/accessibility';
+import { DemoTabsDynamicInsertComponent } from "./dynamic-insert/dynamic-insert";
 
 export const DEMO_COMPONENTS = [
   DemoTabsBasicComponent,
@@ -23,5 +24,6 @@ export const DEMO_COMPONENTS = [
   DemoTabsConfigComponent,
   DemoTabsCustomComponent,
   DemoTabsSelectEventComponent,
-  DemoAccessibilityComponent
+  DemoAccessibilityComponent,
+  DemoTabsDynamicInsertComponent
 ];

demo/src/app/components/+tabs/tabs-section.list.ts

@@ -10,6 +10,7 @@ import { DemoTabsDisabledComponent } from './demos/disabled/disabled';
 import { DemoTabsCustomComponent } from './demos/custom-template/custom-template';
 import { DemoTabsSelectEventComponent } from './demos/select-event/select-event';
 import { DemoAccessibilityComponent } from './demos/accessibility/accessibility';
+import { DemoTabsDynamicInsertComponent } from './demos/dynamic-insert/dynamic-insert';
 
 import { ContentSection } from '../../docs/models/content-section.model';
 import { DemoTopSectionComponent } from '../../docs/demo-section-components/demo-top-section/index';
@@ -63,6 +64,16 @@ export const demoComponentContent: ContentSection[] = [
         html: require('!!raw-loader?lang=markup!./demos/dynamic/dynamic.html'),
         outlet: DemoTabsDynamicComponent
       },
+      {
+        title: 'Dynamic insert tabs content into DOM',
+        anchor: 'dynamic-insert',
+        component: require('!!raw-loader?lang=typescript!./demos/dynamic-insert/dynamic-insert'),
+        html: require('!!raw-loader?lang=markup!./demos/dynamic-insert/dynamic-insert.html'),
+        description: `<p>By default, the tabs contents are added into DOM when page is loaded, for all tabs even not 
+          selected. Dynamic insert tabs into DOM will initialize and add the tab directives only when the tab is activated.
+          Tab contents can be dynamic insert by declaring the tabset component with attribute <code>[dynamic]="true"</code>.</p>`,
+        outlet: DemoTabsDynamicInsertComponent
+      },
       {
         title: 'Pills',
         anchor: 'tabs-Pills',

demo/src/ng-api-doc.ts

@@ -2792,6 +2792,11 @@ export const ngdoc: any = {
         "name": "vertical",
         "type": "boolean",
         "description": "<p>if true tabs will be placed vertically </p>\n"
+      },
+      {
+        "name": "dynamic",
+        "type": "boolean",
+        "description": "<p>if true, tab content will be insert into DOM only if tab is selected</p>\n"
       }
     ],
     "outputs": [],

src/tabs/tab.directive.ts

@@ -23,6 +23,7 @@ export class TabDirective implements OnInit, OnDestroy {
   @Input() disabled: boolean;
   /** if true tab can be removable, additional button will appear */
   @Input() removable: boolean;
+
   /** if set, will be added to the tab's class attribute. Multiple classes are supported. */
   @Input()
   get customClass(): string {

src/tabs/tabset.component.html

@@ -1,15 +1,23 @@
 <ul class="nav" [ngClass]="classMap" (click)="$event.preventDefault()">
-  <li *ngFor="let tabz of tabs" [ngClass]="['nav-item', tabz.customClass || '']"
-      [class.active]="tabz.active" [class.disabled]="tabz.disabled">
+  <li *ngFor="let tabz of tabs"
+      [ngClass]="['nav-item', tabz.customClass || '']"
+      [class.active]="tabz.active"
+      [class.disabled]="tabz.disabled">
     <a href="javascript:void(0);" class="nav-link"
        [attr.id]="tabz.id ? tabz.id + '-link' : ''"
-       [class.active]="tabz.active" [class.disabled]="tabz.disabled"
-       (click)="tabz.active = true">
+       [class.active]="tabz.active"
+       [class.disabled]="tabz.disabled"
+       (click)="selectTab(tabz)">
       <span [ngTransclude]="tabz.headingRef">{{ tabz.heading }}</span>
-      <span *ngIf="tabz.removable" (click)="$event.preventDefault(); removeTab(tabz);" class="bs-remove-tab"> &#10060;</span>
+      <span *ngIf="tabz.removable" (click)="$event.preventDefault(); removeTab(tabz);" class="bs-remove-tab">
+        &#10060;
+      </span>
     </a>
   </li>
 </ul>
+
 <div class="tab-content">
-  <ng-content></ng-content>
+  <ng-container *ngIf="!dynamic">
+    <ng-content></ng-content>
+  </ng-container>
 </div>

src/tabs/tabset.component.ts

@@ -1,4 +1,14 @@
-import { Component, HostBinding, Input, OnDestroy, Renderer2 } from '@angular/core';
+import {
+  AfterContentInit,
+  Component,
+  ContentChild,
+  ElementRef,
+  forwardRef,
+  HostBinding,
+  Input,
+  OnDestroy,
+  Renderer2
+} from '@angular/core';
 
 import { TabDirective } from './tab.directive';
 import { TabsetConfig } from './tabset.config';
@@ -8,12 +18,13 @@ import { TabsetConfig } from './tabset.config';
   selector: 'tabset',
   templateUrl: './tabset.component.html'
 })
-export class TabsetComponent implements OnDestroy {
+export class TabsetComponent implements OnDestroy, AfterContentInit {
   /** if true tabs will be placed vertically */
   @Input()
   get vertical(): boolean {
     return this._vertical;
   }
+
   set vertical(value: boolean) {
     this._vertical = value;
     this.setClassMap();
@@ -24,6 +35,7 @@ export class TabsetComponent implements OnDestroy {
   get justified(): boolean {
     return this._justified;
   }
+
   set justified(value: boolean) {
     this._justified = value;
     this.setClassMap();
@@ -34,12 +46,17 @@ export class TabsetComponent implements OnDestroy {
   get type(): string {
     return this._type;
   }
+
   set type(value: string) {
     this._type = value;
     this.setClassMap();
   }
 
+  /** if true, tab content will be inject to DOM only if tab is selected */
+  @Input() dynamic = false;
+
   @HostBinding('class.tab-container') clazz = true;
+  @ContentChild(forwardRef(() => TabDirective)) content: TabDirective;
 
   tabs: TabDirective[] = [];
   classMap: { [key: string]: boolean } = {};
@@ -49,14 +66,35 @@ export class TabsetComponent implements OnDestroy {
   protected _justified: boolean;
   protected _type: string;
 
-  constructor(config: TabsetConfig, private renderer: Renderer2) {
+  constructor(config: TabsetConfig, private renderer: Renderer2, private elRef: ElementRef) {
     Object.assign(this, config);
   }
 
+  ngAfterContentInit() {
+    if (this.dynamic && typeof this.content !== 'undefined') {
+      const container = this.elRef.nativeElement.querySelector('.tab-content');
+      this.renderer.appendChild(container, this.content.elementRef.nativeElement);
+    }
+  }
+
   ngOnDestroy(): void {
     this.isDestroyed = true;
   }
 
+  selectTab(selectedTab: TabDirective): void {
+    selectedTab.active = true;
+
+    if (this.dynamic) {
+      const container = this.elRef.nativeElement.querySelector('.tab-content');
+
+      while (container.firstChild) {
+        container.firstChild.remove();
+      }
+
+      this.renderer.appendChild(container, selectedTab.elementRef.nativeElement);
+    }
+  }
+
   addTab(tab: TabDirective): void {
     this.tabs.push(tab);
     tab.active = this.tabs.length === 1 && typeof tab.active === 'undefined';