Container and presentational components in Angular - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a presentational component with standalone setup.

Angular

import { Component } from '@angular/core';

@Component({
  selector: 'app-presentational',
  template: `<p>Display data here</p>`,
  standalone: [1]
})
export class PresentationalComponent {}

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

Afalse

Bundefined

Cnull

Dtrue

Attempts:

3 left

💡 Hint

Common Mistakes

Setting standalone to false or omitting it causes the component to require a module.

Using null or undefined is invalid for standalone property.

The standalone property must be set to true to make the component standalone.

2fill in blank

medium

Complete the code to inject a service into a container component using Angular's inject() function.

Angular

import { Component, inject } from '@angular/core';
import { DataService } from './data.service';

@Component({
  selector: 'app-container',
  template: `<app-presentational [data]="data"></app-presentational>`,
  standalone: true,
  imports: []
})
export class ContainerComponent {
  private dataService = [1](DataService);
  data = this.dataService.getData();
}

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

AuseService

Bnew

Cinject

Dprovide

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'new' to create a service instance instead of inject.

Using non-existent functions like 'useService' or 'provide' here.

Angular 17+ uses the inject() function to get service instances inside components.

3fill in blank

hard

Fix the error in the presentational component input binding syntax.

Angular

import { Component, Input } from '@angular/core';

@Component({
  selector: 'app-presentational',
  template: `<p>{{ data }}</p>`,
  standalone: true
})
export class PresentationalComponent {
  @Input() [1]: string = '';
}

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

Adata

BData

CinputData

Dvalue

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different property name than the one bound in the container component.

Capitalizing the property name incorrectly.

The input property name must match the binding name used in the container component, which is data.

4fill in blank

hard

Fill both blanks to correctly pass data from container to presentational component.

Angular

<app-presentational [1]="[2]"></app-presentational>

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

A[data]

Bdata

Cvalue

D[value]

Attempts:

3 left

💡 Hint

Common Mistakes

Using attribute binding without square brackets.

Using mismatched property names.

Use property binding syntax [data] to bind the container's data property to the presentational component's input.

5fill in blank

hard

Fill all three blanks to create a container component that imports the presentational component and passes data correctly.

Angular

import { Component, inject } from '@angular/core';
import { [1] } from './presentational.component';

@Component({
  selector: 'app-container',
  standalone: true,
  imports: [[2]],
  template: `<app-presentational [3]="data"></app-presentational>`
})
export class ContainerComponent {
  data = 'Hello from container';
}

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

APresentationalComponent

C[data]

Ddata

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to import the presentational component.

Not including the component in the imports array.

Using attribute binding instead of property binding.

The container imports the presentational component class, includes it in the imports array, and uses property binding [data] to pass data.

Practice

1. In Angular, what is the main role of a container component?

easy

A. To manage CSS and animations

B. To display UI elements and styles

C. To define routes and navigation

D. To handle data fetching and business logic

Solution

1. Step 1: Understand container component responsibility

   Container components are designed to manage data and logic, such as fetching data or handling user actions.

2. Step 2: Differentiate from presentational components

   Presentational components focus on showing data and UI, not on data handling.

3. Final Answer:

   To handle data fetching and business logic -> Option D

4. Quick Check:

   Container = data and logic [OK]

Hint: Container = data and logic, Presentational = UI only [OK]

Common Mistakes:

• Confusing container with presentational component roles
• Thinking container manages styles or routes
• Assuming container handles only UI display

2. Which of the following is the correct way to pass data from a container to a presentational component in Angular?

easy

A. Use ngModel in container component only

B. @Input() data: any; in presentational, bind in container template

C. @Output() data: any; in presentational, bind in container template

D. Directly modify presentational component's variables from container

Solution

1. Step 1: Identify Angular data flow syntax

   Data flows from container to presentational via @Input() properties.

2. Step 2: Understand binding in container template

   The container passes data by binding to the presentational component's input property in its template.

3. Final Answer:

   @Input() data: any; in presentational, bind in container template -> Option B

4. Quick Check:

   Data down via @Input() [OK]

Hint: Use @Input() to pass data down from container [OK]

Common Mistakes:

• Using @Output() to pass data down instead of events up
• Trying to modify child variables directly
• Confusing ngModel with input binding

3. Given this Angular container component template:

<app-user-list [users]="userArray" (selectUser)="onUserSelect($event)"></app-user-list>

What is the role of (selectUser) here?

medium

A. It defines a CSS class for styling

B. It binds data from container to presentational component

C. It listens to an event emitted by the presentational component

D. It initializes the component's state

Solution

1. Step 1: Recognize Angular event binding syntax

   Parentheses around selectUser indicate event binding from child to parent.

2. Step 2: Understand event emission from presentational component

   The presentational component emits selectUser event, container listens and runs onUserSelect.

3. Final Answer:

   It listens to an event emitted by the presentational component -> Option C

4. Quick Check:

   Parent listens to child event with (event) [OK]

Hint: Parent uses (event) to listen to child events [OK]

Common Mistakes:

• Thinking (selectUser) passes data down
• Confusing event binding with property binding
• Assuming it styles or initializes state

4. What is wrong with this presentational component code snippet?

@Component({
  selector: 'app-item',
  template: `<div>{{item.name}}</div>`
})
export class ItemComponent {
  item: any;
}

medium

A. Missing @Input() decorator on item property

B. Template syntax is incorrect

C. Selector name is invalid

D. Component class should be abstract

Solution

1. Step 1: Check data input declaration

   The presentational component expects data from parent, so item must be decorated with @Input() to receive it.

2. Step 2: Verify template and selector

   Template syntax and selector are valid; no abstract class needed.

3. Final Answer:

   Missing @Input() decorator on item property -> Option A

4. Quick Check:

   @Input() needed to receive data [OK]

Hint: Add @Input() to receive data in presentational component [OK]

Common Mistakes:

• Forgetting @Input() on input properties
• Thinking template interpolation is wrong
• Assuming selector must be different

5. You want to create a container component that fetches a list of products and passes it to a presentational component for display. Which approach best follows Angular container and presentational component patterns?

hard

A. Container fetches products, stores in a variable, passes via @Input(); presentational only displays list

B. Presentational component fetches products and emits events to container

C. Container and presentational both fetch products independently

D. Presentational component manages fetching and state internally

Solution

1. Step 1: Identify container responsibility

   The container should handle fetching data and managing state.

2. Step 2: Identify presentational responsibility

   The presentational component should only display data received via @Input() without fetching or managing state.

3. Final Answer:

   Container fetches products, stores in a variable, passes via @Input(); presentational only displays list -> Option A

4. Quick Check:

   Container = data fetch, Presentational = display [OK]

Hint: Container fetches data, presentational displays it [OK]

Common Mistakes:

• Letting presentational fetch data
• Duplicating data fetch in both components
• Mixing data logic inside presentational