Dart Interview Questions and Answers for freshers

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100 Dart Interview Questions and Answers for Freshers

  1. What is Dart?

    • Answer: Dart is a client-optimized programming language developed by Google. It's used to build fast apps on any platform, including mobile, web, desktop, and server applications. It's known for its ease of use, strong typing, and garbage collection.

  2. What are the key features of Dart?

    • Answer: Key features include its object-oriented nature, support for both null safety and gradual typing, a rich standard library, fast compilation times (especially with Ahead-of-Time (AOT) compilation), and its ability to compile to native code (for performance) or JavaScript (for web browsers).

  3. What is the difference between `var`, `final`, and `const` in Dart?

    • Answer: `var` is used to declare a variable without specifying its type; the type is inferred at compile time. `final` declares a variable that can be assigned only once. `const` declares a compile-time constant; its value must be known at compile time.

  4. Explain the concept of null safety in Dart.

    • Answer: Null safety is a feature that prevents null pointer exceptions by ensuring that variables cannot hold null values unless explicitly allowed. It uses non-nullable types by default, forcing developers to handle potential null values explicitly using techniques like the `?` operator (nullable types) and the `!` operator (non-null assertion).

  5. What are Futures and how are they used in Dart?

    • Answer: Futures represent the eventual result of an asynchronous operation. They're used to handle operations that may take some time to complete, such as network requests. The `.then()` method is used to handle the successful result, while `.catchError()` handles errors.

  6. Explain the concept of Streams in Dart.

    • Answer: Streams are sequences of asynchronous events. They're useful for handling continuous data flows, like user input or data from a sensor. They allow you to listen for events as they occur using `.listen()` and handle them using callbacks.

  7. What is the difference between `async` and `await` keywords?

    • Answer: `async` is used to mark a function as asynchronous, allowing the use of `await`. `await` is used to pause execution of an asynchronous function until a Future completes, making asynchronous code easier to read and write.

  8. How do you handle errors in Dart?

    • Answer: Errors are handled using `try-catch` blocks. The `try` block contains the code that might throw an exception, and the `catch` block handles the exception if it occurs. `finally` blocks (optional) contain code that always executes, regardless of whether an exception is thrown.

  9. What are Isolates in Dart?

    • Answer: Isolates are independent workers that run concurrently with the main program. They provide true parallelism, allowing you to perform CPU-bound tasks without blocking the UI. Communication between isolates happens through message passing.

  10. What are some common Dart data structures?

    • Answer: Common data structures include Lists (dynamically sized arrays), Sets (collections of unique elements), Maps (key-value pairs), and Queues (FIFO data structures).

  11. Explain the difference between a class and an abstract class in Dart.

    • Answer: A class is a blueprint for creating objects. An abstract class cannot be instantiated directly; it serves as a template for subclasses to implement its abstract methods.

  12. What is polymorphism and how is it achieved in Dart?

    • Answer: Polymorphism allows objects of different classes to be treated as objects of a common type. In Dart, it's achieved through inheritance and interfaces.

  13. How do you create a generic function in Dart?

    • Answer: Use type parameters within angle brackets `` to define a generic function that can work with various data types.

  14. Explain the concept of mixins in Dart.

    • Answer: Mixins are a way to reuse code across multiple classes without using inheritance. They add functionality to a class without creating a subclass relationship.

  15. How do you handle asynchronous operations in Dart?

    • Answer: Using Futures and async/await keywords provides elegant handling of asynchronous operations, ensuring efficient concurrency.

  16. What are the different ways to make an HTTP request in Dart?

    • Answer: Dart provides `http` package which offers functionalities to make GET, POST, PUT, DELETE requests along with error handling and custom headers.

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