Dynamic component loading in Angular - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the Angular core module needed for dynamic component loading.

Angular

import { [1] } from '@angular/core';

Drag options to blanks, or click blank then click option'

ANgModule

BInjectable

CComponentFactoryResolver

DDirective

Attempts:

3 left

💡 Hint

Common Mistakes

Importing NgModule instead of ComponentFactoryResolver

Using Injectable which is for services

Using Directive which is for attribute or structural directives

The ComponentFactoryResolver is used to create component factories for dynamic loading.

2fill in blank

medium

Complete the code to get a reference to the container where the dynamic component will be inserted.

Angular

@ViewChild('container', { read: [1] }) containerRef!: ViewContainerRef;

Drag options to blanks, or click blank then click option'

ATemplateRef

BViewContainerRef

CElementRef

DRenderer2

Attempts:

3 left

💡 Hint

Common Mistakes

Using ElementRef which references DOM elements but not containers

Using TemplateRef which is for templates, not containers

Using Renderer2 which is for DOM manipulation

ViewContainerRef is needed to insert components dynamically into the view.

3fill in blank

hard

Fix the error in the code to create a component dynamically using the resolver.

Angular

const factory = this.componentFactoryResolver.[1](MyDynamicComponent);
this.containerRef.clear();
this.containerRef.createComponent(factory);

Drag options to blanks, or click blank then click option'

AresolveComponentFactory

BcreateComponentFactory

CgetComponentFactory

DmakeComponentFactory

Attempts:

3 left

💡 Hint

Common Mistakes

Using non-existent methods like createComponentFactory

Using getComponentFactory which does not exist

Using makeComponentFactory which is invalid

The correct method to get a component factory is resolveComponentFactory.

4fill in blank

hard

Fill both blanks to clear the container and insert the new component.

Angular

this.containerRef.[1]();
this.containerRef.[2](factory);

Drag options to blanks, or click blank then click option'

Aclear

BcreateComponent

Cinsert

Dremove

Attempts:

3 left

💡 Hint

Common Mistakes

Using remove instead of clear to empty the container

Using insert instead of createComponent to add the component

First, clear the container with clear(), then create the component with createComponent().

5fill in blank

hard

Fill all three blanks to define a dynamic component loader method that creates and inserts a component.

Angular

loadComponent() {
  const factory = this.[1].[2](DynamicComponent);
  this.containerRef.[3]();
  this.containerRef.createComponent(factory);
}

Drag options to blanks, or click blank then click option'

AcomponentFactoryResolver

BresolveComponentFactory

Cclear

DcreateComponent

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong service name for the resolver

Skipping clearing the container before insertion

Using wrong method names

The method uses componentFactoryResolver to get the factory, calls resolveComponentFactory, then clears the container before creating the component.

Practice

1. What is the main purpose of dynamic component loading in Angular?

easy

A. To add components to the view while the app is running

B. To statically declare all components in the template

C. To improve CSS styling of components

D. To replace Angular modules with components

Solution

1. Step 1: Understand dynamic component loading

   Dynamic component loading means adding components to the app view during runtime, not just at compile time.

2. Step 2: Compare options

   Only To add components to the view while the app is running describes adding components while the app runs. Other options describe static or unrelated concepts.

3. Final Answer:

   To add components to the view while the app is running -> Option A

4. Quick Check:

   Dynamic loading = add components at runtime [OK]

Hint: Dynamic loading means adding components during app run [OK]

Common Mistakes:

• Confusing dynamic loading with static template declaration
• Thinking it changes CSS or modules
• Assuming it replaces Angular modules

2. Which Angular service is used to insert a dynamic component into the view?

easy

A. Renderer2

B. HttpClient

C. ViewContainerRef

D. NgModuleRef

Solution

1. Step 1: Identify the service for dynamic insertion

   ViewContainerRef provides a container where components can be dynamically added or removed.

2. Step 2: Eliminate other options

   Renderer2 is for DOM manipulation, HttpClient for HTTP calls, NgModuleRef for module references, none for dynamic component insertion.

3. Final Answer:

   ViewContainerRef -> Option C

4. Quick Check:

   Dynamic insertion uses ViewContainerRef [OK]

Hint: Use ViewContainerRef to insert dynamic components [OK]

Common Mistakes:

• Choosing Renderer2 which is for DOM, not components
• Confusing HttpClient with component loading
• Using NgModuleRef incorrectly

3. Given this code snippet, what will be the output in the browser?

const componentRef = viewContainerRef.createComponent(MyComponent);
componentRef.instance.title = 'Hello';

Assuming MyComponent displays {{ title }} in its template.

medium

A. The component will load but title will be empty

B. The text 'Hello' will appear where the component is loaded

C. Nothing will appear because the component is not attached

D. An error because title is not a valid property

Solution

1. Step 1: Understand createComponent and instance property

   createComponent adds the component to the view. Setting instance.title assigns the property used in the template.

2. Step 2: Predict rendered output

   Since {{ title }} is displayed, and title is set to 'Hello', the text 'Hello' will appear.

3. Final Answer:

   The text 'Hello' will appear where the component is loaded -> Option B

4. Quick Check:

   Set instance property = visible text [OK]

Hint: Setting instance properties updates displayed content [OK]

Common Mistakes:

• Thinking component is not attached after createComponent
• Assuming property must be declared differently
• Ignoring that instance properties affect template

4. What is wrong with this code snippet for dynamic component loading?

@ViewChild('container', { read: ViewContainerRef }) containerRef!: ViewContainerRef;

load() {
  const comp = this.containerRef.createComponent(SomeComponent);
  comp.instance.data = 'Test';
}

medium

A. ViewChild should not use read option

B. Using createComponent without importing ComponentFactoryResolver

C. Cannot assign data property on instance

D. Missing #container template reference in HTML

Solution

1. Step 1: Check ViewChild usage

   ViewChild with #container expects a matching template reference variable in HTML.

2. Step 2: Identify missing template reference

   If #container is missing in the template, containerRef will be undefined, causing runtime errors.

3. Final Answer:

   Missing #container template reference in HTML -> Option D

4. Quick Check:

   ViewChild needs matching template ref [OK]

Hint: Always add matching #ref in template for ViewChild [OK]

Common Mistakes:

• Assuming ComponentFactoryResolver is needed in Angular 14+
• Thinking instance properties can't be assigned
• Misusing read option in ViewChild

5. You want to load different components dynamically based on user input. Which approach correctly handles this scenario in Angular?

hard

A. Use a single ViewContainerRef and call createComponent() with the chosen component type each time, clearing previous components

B. Declare all possible components in the template and use *ngIf to show/hide them

C. Create components manually with new keyword and append to DOM

D. Use Angular modules to switch components dynamically without ViewContainerRef

Solution

1. Step 1: Understand dynamic component switching

   Using ViewContainerRef with createComponent allows loading different components at runtime by clearing old ones and adding new.

2. Step 2: Evaluate other options

   Declare all possible components in the template and use *ngIf to show/hide them is static and less flexible. Create components manually with new keyword and append to DOM bypasses Angular and breaks framework rules. Use Angular modules to switch components dynamically without ViewContainerRef misunderstands modules' role.

3. Final Answer:

   Use a single ViewContainerRef and call createComponent() with the chosen component type each time, clearing previous components -> Option A

4. Quick Check:

   Dynamic switching = clear + createComponent [OK]

Hint: Clear container then create chosen component dynamically [OK]

Common Mistakes:

• Using static *ngIf instead of dynamic loading
• Trying to create components with new keyword
• Confusing modules with dynamic component loading