**Course Title:** Ruby Programming: From Basics to Advanced Techniques **Section Title:** Data Structures: Arrays, Hashes, and Sets **Topic:** Working with Arrays: Creation, Manipulation, and Iteration ### Overview of Arrays in Ruby In Ruby, an array is a collection of objects that can be of any data type, including strings, integers, floats, and other arrays. Arrays are used to store and manipulate collections of data. They are ordered, meaning that the position of each element matters, and the order in which elements are stored is preserved. ### Creating Arrays in Ruby There are several ways to create arrays in Ruby: 1. **Using the `[]` notation**: This is the most common way to create an array. You simply enclose the elements you want to include in the array in square brackets (`[]`). ```ruby fruits = ['apple', 'banana', 'cherry'] ``` 2. **Using the `Array.new` method**: This method creates a new array with the specified size and default value. ```ruby numbers = Array.new(5, 0) # => [0, 0, 0, 0, 0] ``` 3. **Using the `%w()` notation**: This notation is used to create an array of strings without quotes. ```ruby colors = %w(red green blue) ``` ### Accessing Array Elements Array elements are accessed using their index, which is a zero-based integer value. ```ruby fruits = ['apple', 'banana', 'cherry'] puts fruits[0] # => apple puts fruits[-1] # => cherry (negative index starts from the end) ``` ### Manipulating Arrays Arrays can be manipulated in several ways: 1. **Adding elements to the end of the array**: Use the `push` or `<<` method. ```ruby numbers = [1, 2, 3] numbers.push(4) # => [1, 2, 3, 4] numbers << 5 # => [1, 2, 3, 4, 5] ``` 2. **Removing the last element from the array**: Use the `pop` method. ```ruby numbers = [1, 2, 3] numbers.pop # => 3 (returns the last element) ``` 3. **Adding elements to the beginning of the array**: Use the `unshift` method. ```ruby numbers = [1, 2, 3] numbers.unshift(0) # => [0, 1, 2, 3] ``` 4. **Removing the first element from the array**: Use the `shift` method. ```ruby numbers = [1, 2, 3] numbers.shift # => 1 (returns the first element) ``` ### Iterating Over Array Elements There are several ways to iterate over array elements: 1. **Using the `each` method**: ```ruby fruits = ['apple', 'banana', 'cherry'] fruits.each do |fruit| puts fruit end # Output: # apple # banana # cherry ``` 2. **Using the `map` method**: ```ruby numbers = [1, 2, 3] squared_numbers = numbers.map { |number| number * number } puts squared_numbers # => [1, 4, 9] ``` 3. **Using the `select` method**: ```ruby numbers = [1, 2, 3, 4, 5] even_numbers = numbers.select { |number| number.even? } puts even_numbers # => [2, 4] ``` For more information on Ruby arrays, refer to the official Ruby documentation: [https://ruby-doc.org/core-3.1.0/Array.html](https://ruby-doc.org/core-3.1.0/Array.html) ### Key Takeaways * Arrays are collections of objects that can be of any data type. * Use `[]`, `Array.new`, and `%w()` notation to create arrays. * Access array elements using their index. * Use `push`, `<<`, `pop`, `unshift`, and `shift` methods to manipulate arrays. * Use `each`, `map`, and `select` methods to iterate over array elements. ### Next Topic: Using Hashes for Key-Value Pairs If you have any questions or need help with any concept, feel free to ask.