Dart Interview Questions and Answers for 7 years experience

1. What is Dart? What are its key features and advantages?

   • Answer: Dart is a client-optimized programming language developed by Google. Its key features include: being object-oriented, garbage-collected, and supporting both ahead-of-time (AOT) and just-in-time (JIT) compilation. Advantages include fast development cycles (due to JIT), high performance (due to AOT), a strong ecosystem (Flutter), and a relatively easy learning curve for developers familiar with other object-oriented languages. It's versatile enough for both front-end (Flutter) and back-end (with frameworks like Aqueduct) development.

2. Explain the difference between AOT and JIT compilation in Dart.

   • Answer: AOT (Ahead-of-Time) compilation translates Dart code into native machine code before the program runs. This results in faster execution speeds because the code doesn't need to be compiled at runtime. JIT (Just-in-Time) compilation translates Dart code into machine code during runtime. This enables features like hot reload, which allows for faster development cycles. Flutter uses both: JIT for development and AOT for production releases.

3. What are Isolates in Dart, and why are they useful?

   • Answer: Isolates in Dart are independent workers that run concurrently but do not share memory. They communicate through message passing. This is crucial for avoiding race conditions and deadlocks in concurrent programming, allowing for true parallelism. They're particularly beneficial for I/O-bound tasks, preventing blocking the main thread and maintaining responsiveness.

4. Explain the concept of Futures and Async/Await in Dart.

   • Answer: Futures represent the eventual result of an asynchronous operation. They handle asynchronous code gracefully. Async/Await provides a more synchronous-looking way to write asynchronous code, making it easier to read and reason about. `async` marks a function as asynchronous, and `await` pauses execution until a Future completes, receiving its value or error.

5. Describe different ways to handle errors in Dart.

   • Answer: Dart uses `try-catch` blocks to handle exceptions. `try` contains the code that might throw an exception, `catch` handles the exception, and `finally` (optional) executes regardless of whether an exception occurred. Custom exceptions can be created by extending the `Exception` class. Futures can also handle errors through `.catchError` or by using `try-catch` within an `async` function.

6. What are Mixins in Dart and how do they differ from inheritance?

   • Answer: Mixins are a way to reuse code across classes without using inheritance. They allow a class to inherit functionality from multiple sources without the limitations of multiple inheritance (e.g., the diamond problem). Inheritance creates an "is-a" relationship, while mixins provide a "has-a" or "uses-a" relationship, offering more flexibility in code reuse.

7. Explain the difference between `const` and `final` in Dart.

   • Answer: `final` variables can only be assigned once, but their value can be computed at runtime. `const` variables are compile-time constants; their values must be known at compile time. `const` implies `final`.

8. What is the purpose of the `void` keyword in Dart?

   • Answer: The `void` keyword indicates that a function doesn't return any value. It's similar to `void` in other C-style languages.

9. How do you handle null values in Dart to prevent null pointer exceptions?

   • Answer: Dart's null safety features help avoid null pointer exceptions. The `?` operator denotes nullable types. The `!` operator asserts that a value is not null (use cautiously!). Null checks (`if (value != null)`) and the null-aware operator (`?.`) are essential for safe null handling. The `??` operator (null-aware assignment) provides a default value if the expression is null.

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