This interview Q&A cheat sheet offers a quick, easy reference to key interview strategies and commonly asked questions. Use it to refresh your preparation and boost your confidence before any interview!
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Ruby is object-oriented language, which means that everything in Ruby is an object, even the most basic data types.
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- It is simple & readable language
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- Implemented based on python and perl
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- Ruby follows convention over configuration and DRY
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COC: Reduces need for extensive setup & makes coding quicker & simple.
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Ex: method names and variable names should match the logic
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DRY: Encourage reducing repetition in code to make it more maintainable & efficient.
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Developed by "Yukihiro Matsumoto" in the mid - 1990s in Japan.
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It is Object-oriented programming language known for easy syntax & focus on simplicity & productivity.
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Supports for blocks, iterators, mixins for code reuse.
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Follows DRY & COC
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Everything in ruby is object including datatypes because, language is designed to treat all entities uniformly.
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Allowing for consistent behaviour & functionality across datatypes.
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Use to store values in memory, allowing to access & modify data as you need.
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Types
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Local variable: Accessible within scope, they defined within a method or block
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Instance variable(@): Associated with instance of class, accessible across methods in instance.
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Class variable(@@): Accessible among all instance of class.
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Global variable($): Accessed anywhere in program.
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Class:A blueprint for creating objects; it defines attributes and methods. In Ruby, classes are created using the class keyword. Object: An instance of a class, holding unique data and behaviors as defined by its class.
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Encapsulation: Bundles data and methods within calss, controlling access to them Ex: attr_reader, attr_writer, attr_accessor
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Inheritance: Allows class to inherit behaviours & attributes from another class.
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Polymorphism: It is the ability to represent an operator or function in different ways
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Abstraction: It hides the complexity of a class by modelling classes appropriate to the problem.
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1. Strings: Represented by single('Hi') or double quotes("Hi")
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2. Numbers: It can be integers(10) or float(3.14)
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3. Arrays: Collection of objects. [1,2,3]
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4. Hashes: Key-value pair. {"name"=>"Jhon"}
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5. Symbols: Light weight, immutable strings are used as identifiers (:name
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It is special instance method in ruby called when a new object is created.
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It is a command line tool allows easily to install, manage & work with different ruby environments
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Loops allows you to repeat set of instructions multiple times.
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1. for loop: Used to iterator over range/ collection
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2. while loop: Runs code as long as condition is true.
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3. Until loop: Opposite of while loop. Runs code until a specific condition becomes true.
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4. Nested for loop: For loop inside other fo loop. Allows to perform iterators over multi-dimensional DS.
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* Array is collection of objects, they hold objects like integer, number, hash, string, symbol etc..
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* Index starts with 0
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Operators are symbols used to perform operations
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Unary Operator: ! ~ +
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Arithmetic Operator: + - / % **
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Assignment Operator: = += -= = /= %= **=
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Comparision Operator: == != > >= < <= ===
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Bitwise Operator: & | ^ ~ << >>
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Logical Operator: && || ! and or
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Ternary Operator: ? !
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Range: .. ...
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* Hash is Data structure which stored key-value pair
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* Useful for storing data with unique identifiers(key), as you can access by key
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Object is instance of class that combines data(attributes) & behaviour(methods).
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Everything in ruby is object link numbers, strings, arrays etc.
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Set of instructions/ code that perform specific task.
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Used to encapsulate reusable code, making program more organised
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They can take arguments, perform actions & return value.
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Class methods: Methods belongs to class itself, allowing them to call without creating instance of class.
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* We use self keyword in class
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Instance methods: Belongs to instance of class & can only called on an object created from that class.
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Overloading: A class containing more methods with same name with different parameters
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Overriding: Parent class and child class having same name with differnt functionalities. when you call, it executes parent class only.
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Constants are variables that cannot change once we declare.
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Iterators are methods that naturally loop over a give set of data & allow you to operate on each element in the collection.
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Modules: Containers for methods and constants that help organize code and avoid naming conflicts. Modules can't create objects on their own.
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Mixins: A technique for adding module methods to a class as instance methods, allowing multiple classes to share functionality without inheritance.
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Hash: Key-Value pair combination. Key should be unique
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Array: Collection of stings, numbers. Index starts with '0'. It is Heterogenous
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Class: Class is a blueprint of object
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* Contains methods & attributes for its instance.
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* These methods are used as objects
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Module: It is collection of class
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- Self refers to current object instance
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- It is used to access methods & variables within object itself.
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nil: Object represents nothing or no value
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false: Boolean value that explicitly represents falsehood.
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== operator: Checks value equality. Compare 2 value objects to see if they are same.
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=== Operator(Case equality): Used in case statement & check whether object is in or matches another object.
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Ex: Numeric === 5 #true because 5 is number
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sub: It will replace first matching item
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Ex: I love cats. cats are great
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O/p: I love dogs. cats are great
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gsub: It will replace all matching item in sentence
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Ex: I love cats. cats are great
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O/p: I love dogs. dogs are great
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puts: Output a string with newline at end.
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print: Output a string without newline
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p: Output value is more readable form, shows exact values including quotes.
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Proc(Procedure): It is code block that stored in local variable, not in method.
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Lamda: It is Short block of code which takes in parameters & returns value.
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Include: We need objects to call methods
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Extend: We dont need to objects to call methods, directly we can call with class.
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eql?: Used in hases to check if key have same values & type, allowing them match.
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Ex: puts "hello".eql?("hello") #True
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equal?:Used for key comparison. Checks if two variables reference same object in memory.
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Ex: a="hello, c=a
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puts a.equal?(c) #True(same object) |
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Each: executes the given block for each element of the array, then returns the array itself.
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Map: executes the given block for each element of the array, but returns a new array whose values are the return values of each iteration of the block.
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