Crystal Interview Questions and Answers for 2 years experience

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100 Interview Questions and Answers for 2 Years Experience: Crystal

  1. What is Crystal?

    • Answer: Crystal is a statically-typed, compiled programming language that blends the elegance and performance of C with the developer friendliness of Ruby. It aims to be a performant language that's easy to learn and use, avoiding the garbage collection pauses often associated with dynamically-typed languages like Ruby.

  2. What are the key features of Crystal?

    • Answer: Key features include static typing, compile-time metaprogramming, automatic memory management (without garbage collection pauses), concurrency through fibers, and a syntax heavily inspired by Ruby.

  3. How does Crystal's memory management differ from languages like Java or Go?

    • Answer: Crystal uses a sophisticated reference counting system with cycle detection to manage memory. Unlike garbage collection in Java or Go, this doesn't require stopping the program to perform cleanup, leading to more consistent performance. However, it's important to note that improper handling of references can lead to memory leaks.

  4. Explain the concept of "fibers" in Crystal.

    • Answer: Fibers in Crystal are lightweight concurrency primitives. They allow you to write concurrent code without the overhead of creating and managing separate OS threads. They are managed by the Crystal runtime and allow for efficient context switching between tasks.

  5. What is the role of the `shard` in Crystal?

    • Answer: A shard is Crystal's equivalent of a package or library. It's a self-contained unit of code that can be easily shared and reused in other Crystal projects. The Crystal community uses shards extensively through the Crystal shard repository.

  6. How do you handle errors in Crystal?

    • Answer: Crystal uses exceptions for error handling, similar to other languages like Ruby, Java and Python. Exceptions are raised when an error occurs and can be caught using `begin`, `rescue`, and `ensure` blocks. Crystal also encourages the use of types to prevent errors at compile time.

  7. Describe your experience with Crystal's type system.

    • Answer: (This answer should be tailored to the candidate's experience. A good answer would discuss specific types used, type inference, and how the type system helped catch bugs during development.) Example: "I've found Crystal's static typing system very beneficial. It caught many errors at compile time that would have been difficult to find in a dynamically typed language. I've worked extensively with types like `Int32`, `String`, `Array`, and custom structs, leveraging type inference to reduce boilerplate code."

  8. How does Crystal's compile-time metaprogramming work? Give an example.

    • Answer: Crystal's powerful compile-time metaprogramming allows code generation and manipulation during compilation. This is achieved through macros. A simple example would be creating a macro to generate getter and setter methods for struct fields automatically. (Candidate should be able to provide a basic macro example or describe a scenario where they've used compile-time metaprogramming.)

  9. Explain the difference between `struct` and `class` in Crystal.

    • Answer: `struct`s are value types; when you assign a `struct` to a variable, it creates a copy. `class`es are reference types; multiple variables can refer to the same object. `class`es support inheritance, while `struct`s do not.

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