Dart Programming Language Interview Questions: A Comprehensive Guide

Mastering Dart?

This complete guide, carefully put together with the newest details and information, will give you the confidence to ace your Dart programming language interview.

Dive deep into the world of Dart with a curated selection of interview questions, covering everything from fundamental concepts to advanced topics

Ready to shine?

Let’s embark on this journey together.

Dart A Powerful Tool for Modern Developers

Developed by Google, Dart has emerged as a versatile and efficient programming language particularly for building web server-side, and mobile applications. Its emphasis on performance, ease of use, and scalability makes it a top choice for developers worldwide.

Unleashing the Power of Dart

To effectively utilize Dart’s capabilities, a strong understanding of its core concepts and best practices is essential. This guide provides you with the knowledge and skills to excel in your Dart programming interview.

Navigating the Interview Landscape

Junior Dart Interview Questions

• It is meant to print the numbers from 1 to 10 with the following Dart code. However, it is currently not working. Identify and fix the issue.

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  void main() {  for (var i = 1; i < 11; i++) {    print(i);  }}

  Answer: The code snippet provided is correct and will print the numbers from 1 to 10. There is no issue with it.

• What is the main reason to use Dart, and what platform does it mostly work with?

  Answer: Dart is a general-purpose programming language that is mostly used to make apps for phones and the web. You can write Flutter apps in this language. Flutter is a user interface framework mainly made for mobile platforms like Android and iOS.

• Question: The following Dart code snippet is supposed to concatenate two strings and print the result. However, it is not producing the expected output. Identify and fix the issue.

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  void main() {  String firstName = "John";  String lastName = "Doe";  String fullName = firstName + lastName;  print(fullName);}

  Answer: To concatenate two strings in Dart, you can use the + operator. However, in the given code snippet, the + operator is not adding a space between the firstName and lastName. To fix this, you can add a space manually between the strings:

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  void main() {  String firstName = "John";  String lastName = "Doe";  String fullName = firstName + " " + lastName;  print(fullName);}

• Question: What is the purpose of using the async and await keywords in Dart?

  Answer: The async and await keywords in Dart are used in asynchronous programming to work with functions that perform potentially time-consuming tasks, such as making network requests or accessing databases. By marking a function as async, it can use the await keyword to wait for the completion of other asynchronous operations without blocking the execution. This allows for more efficient and responsive code, especially in UI-driven applications.

• Question: The following Dart code snippet is supposed to calculate the sum of all elements in the numbers list. However, it is not returning the correct result. Identify and fix the issue.

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  void main() {  List<int> numbers = [1, 2, 3, 4, 5];  int sum = 0;  for (var i = 0; i <= numbers.length; i++) {    sum += numbers[i];  }  print(sum);}

  Answer: The issue in the code is with the loop condition in the for loop. The condition should be i < numbers.length instead of i <= numbers.length to avoid accessing an index out of range. Here’s the corrected code:

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  void main() {  List<int> numbers = [1, 2, 3, 4, 5];  int sum = 0;  for (var i = 0; i < numbers.length; i++) {    sum += numbers[i];  }  print(sum);}

• Question: What is the purpose of using the final keyword in Dart?

  Answer: In Dart, the final keyword is used to declare a variable whose value cannot be changed once assigned. It is similar to const, but the value of a final variable can be determined at runtime. Using final allows you to ensure that a variable remains constant after its initialization, providing immutability and better performance in some cases.

• Question: The following Dart code snippet is intended to calculate the factorial of a given number. However, it is currently not producing the correct result. Identify and fix the issue.

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  void main() {  int number = 5;  int factorial = 1;  for (var i = 2; i <= number; i++) {    factorial *= i;  }  print("The factorial of $number is $factorial");}

  Answer: The code snippet provided correctly calculates the factorial of a given number. There is no issue with it.

• Question: What is the difference between a List and a Set in Dart?

  Answer: In Dart, a List is an ordered collection of elements that allows duplicate values. Elements in a list can be accessed using their index. On the other hand, a Set is an unordered collection of unique elements. It does not allow duplicate values, and the order of elements is not guaranteed. Sets are useful when you need to ensure uniqueness and perform operations like union, intersection, and difference on collections.

• Question: The following Dart code snippet is intended to check if a given number is even or odd. However, it is not returning the correct result. Identify and fix the issue.

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  void main() {  int number = 7;  if (number % 2 = 0) {    print("$number is even");  } else {    print("$number is odd");  }}

  Answer: In the given code snippet, there is a mistake in the condition of the if statement. Instead of using the assignment operator =, the equality operator == should be used. Here’s the corrected code:

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  void main() {  int number = 7;  if (number % 2 == 0) {    print("$number is even");  } else {    print("$number is odd");  }}

• Question: What are some advantages of using Dart for mobile app development compared to other programming languages?

  Answer: Some advantages of using Dart for mobile app development, particularly with Flutter, include:

  • Cross-platform development: Dart allows you to build mobile apps for both Android and iOS using a single codebase, reducing development time and effort.
  • Hot Reload: Dart’s Hot Reload feature in Flutter enables developers to see the changes made in the code immediately reflected in the app, allowing for faster iteration and debugging.
  • Performance: Dart’s Just-in-Time (JIT) compilation during development and Ahead-of-Time (AOT) compilation during production result in efficient and performant mobile apps.
  • Rich UI and Customization: Dart and Flutter provide a rich set of customizable UI widgets, enabling developers to create visually appealing and highly interactive mobile apps.
  • Community and Ecosystem: Dart and Flutter have a growing community and ecosystem, with a wide range of packages and libraries available, making it easier to leverage existing solutions for various app requirements.

Intermediate Dart Interview Questions

• Question: The following Dart code snippet is intended to calculate the sum of two numbers. However, it is not producing the correct result. Identify and fix the issue.

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  int calculateSum(int a, int b) {  int sum = a + b;  return sum;}void main() {  int result = calculateSum(2, 3);  print(result);}

  Answer: The code is correct. It correctly calculates the sum of two numbers. The output will be 5.

• Question: What is a constructor in Dart? Explain with an example.

  Answer: A constructor in Dart is a special method used for creating objects of a class. It initializes the object’s state when it is created. Dart supports two types of constructors: default constructors and named constructors.

  Example:

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  class Person {  String name;  int age;  Person(this.name, this.age); // Default constructor  Person.fromBirthYear(this.name, int birthYear) {    age = DateTime.now().year - birthYear;  } // Named constructor  void sayHello() {    print('Hello, my name is $name.');  }}void main() {  var person1 = Person('Alice', 25); // Using the default constructor  person1.sayHello();