Ruby Interview Questions and Answers for experienced

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100 Ruby Interview Questions and Answers

  1. What is the difference between `==` and `===` in Ruby?

    • Answer: `==` checks for equality, while `===` performs case equality. `==` uses the `eql?` method, which usually checks for value equality. `===` is used for pattern matching and its behavior depends on the object it's called on. For example, with regular expressions, `===` checks if the string matches the pattern. With classes, it checks if the object is an instance of the class.

  2. Explain the concept of metaprogramming in Ruby.

    • Answer: Metaprogramming is the ability of a program to manipulate itself. In Ruby, this is achieved through features like `method_missing`, `define_method`, `class_eval`, and `instance_eval`. It allows you to dynamically modify the behavior of classes and objects at runtime, creating very flexible and extensible code. Examples include creating dynamic methods, modifying existing methods, and adding attributes on the fly.

  3. What are blocks, procs, and lambdas in Ruby? How do they differ?

    • Answer: Blocks are anonymous chunks of code passed to methods. Procs are objects that encapsulate blocks of code, allowing you to store and reuse them. Lambdas are similar to procs, but they have stricter argument handling and return behavior. Key differences include how they handle arguments (lambdas enforce the correct number of arguments), and how they return from enclosing methods (lambdas return to the caller of the lambda, while procs return from the method they are called within).

  4. Explain Ruby's garbage collection mechanism.

    • Answer: Ruby uses a mark-and-sweep garbage collector. It periodically identifies objects that are no longer referenced by any part of the program and reclaims the memory they occupy. This prevents memory leaks and ensures efficient memory management. The specifics of the GC can be tuned through environment variables or within the Ruby code itself.

  5. Describe the purpose and usage of `attr_accessor`, `attr_reader`, and `attr_writer`.

    • Answer: These are macros that simplify the creation of getter and setter methods for instance variables. `attr_accessor` creates both getter and setter methods, `attr_reader` creates only the getter, and `attr_writer` creates only the setter. They are commonly used to define properties of a class concisely.

  6. What are mixins in Ruby and how are they used?

    • Answer: Mixins provide a way to include the functionality of one module into another class. This allows you to share code between classes without using inheritance. It promotes code reuse and avoids the limitations of multiple inheritance (which Ruby doesn't directly support).

  7. Explain the difference between `include` and `extend` in Ruby.

    • Answer: `include` adds the methods of a module as instance methods to a class. `extend` adds the methods of a module as class methods to a class. `include` is used for adding functionality to individual objects of a class, while `extend` adds functionality to the class itself.

  8. How does Ruby handle exceptions? Explain the `begin`, `rescue`, `ensure`, and `else` blocks.

    • Answer: Ruby uses `begin`, `rescue`, `ensure`, and `else` blocks to handle exceptions. The `begin` block contains the code that might raise an exception. The `rescue` block catches specific exceptions and handles them. The `ensure` block always executes, regardless of whether an exception occurred. The `else` block executes only if no exception occurred.

  9. What are some common Ruby design patterns you have used? Give examples.

    • Answer: (This answer will vary based on experience. Examples include Model-View-Controller (MVC), Singleton, Factory, Observer, Strategy, Decorator, etc. The candidate should provide specific examples of how they've used these patterns in their projects.)

  10. Explain the concept of "duck typing" in Ruby.

    • Answer: Duck typing focuses on an object's behavior rather than its class. If an object "walks like a duck and quacks like a duck," it's treated as a duck, regardless of its actual class. This makes code more flexible and reduces the reliance on strict type checking.

  11. What are the differences between Ruby on Rails and other Ruby frameworks?

    • Answer: [Detailed comparison of Rails with Sinatra, Hanami, etc.]

  12. Explain different ways to handle database interactions in Ruby.

    • Answer: [Discussion of ORMs like ActiveRecord, Sequel, and direct database interaction using libraries.]

  13. How do you handle concurrency and parallelism in Ruby?

    • Answer: [Explanation of threads, processes, and libraries like `concurrent-ruby`.]

  14. Discuss different approaches to testing in Ruby.

    • Answer: [Description of unit testing, integration testing, and different testing frameworks like RSpec, Minitest.]

  15. How do you manage dependencies in Ruby projects?

    • Answer: [Explanation of Bundler and Gemfiles.]

  16. Explain your experience with version control systems like Git.

    • Answer: [Discussion of branching strategies, merging, conflict resolution, etc.]

  17. How do you approach debugging in Ruby?

    • Answer: [Description of debugging tools, techniques, and strategies.]

  18. Explain your understanding of Ruby's object model.

    • Answer: [In-depth explanation of classes, objects, inheritance, modules, and metaclasses.]

  19. Describe your experience with RESTful APIs and how you would design one in Ruby.

    • Answer: [Discussion of API design principles, HTTP methods, and Ruby frameworks for building APIs like Rails or Sinatra.]

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