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Exercise 05: Angular Components - Quiz app

Solution Video

Introduction

In this exercise we will create a quiz application that will ask the user a list of single choice questions and will finally present a summary and score.

Instructions

Step 1: Data model

Create a Question interface containing the following properties

  • caption (string) the content of the question
  • answers (string[]) the possible answsers
  • correctAnswerIndex (number) the index of the correct answer

Create an Answer interface

  • userAnswer (number)
  • isCorrect (boolean)

Also create some DATA in json format, an array of questions.

Step 2: The app component state

The root component is going to serve as the only smart component in the application. It will hold all the state and all the actions.

The state includes:

  • An array of questions
  • An array of answers the user has provided

Step 3: The app component methods

The actions are:

  • Reset quiz - empties the array of answers
  • Add an answer (index) - receives an answer to the current question and adds it to the array of answers

Step 4: The app component computed data

Create the following computed values from the core state:

  • The index of the current question (you can derive it from the size of the answers array)
  • The current question itself
  • Is the quiz over (it is when there are as many asnwers as questions)
  • Total correct answers
  • Current score (total correct answers divided by total questions)

Step 5: Question presenter component

Create a presentation component, that receives a question as input and:

  1. Displays the question
  2. Displays the possible answers
  3. When the user clicks one of the answers, raises an event with the index of the answer as payload

In AppComponent use the new component to display the current question, and respond to the event

Step 6: Progress indicator component

Create a presentation component, that receives 2 inputs:

  • Total
  • Value

The component will visually display the ratio between the value and the total.

  • Create a computed ratio signal
  • Create a computed percentage signal the converts the ratio into percentage string (!!)
  • Now use the percentage string and CSS to paint a proportional area of the component

Use this new component in the AppComponent to present to the user the progress of the quiz

Step 7: Summary component

Create a presentation compontant that receives 1 input

  • Score
  • Also implement a reset output event
  • Present it along with a message that the quiz is over an a button that allows to reset the quiz and start over
  • In App Component when the quiz is over, present the summary component instead of the question presenter and the progress indicator
  • In AppComponent also catch and implement the reset event