**Course Title:** Ruby Programming: From Basics to Advanced Techniques **Section Title:** Data Structures: Arrays, Hashes, and Sets **Topic:** Common array and hash methods ### Introduction In the previous topics, we covered the basics of arrays, hashes, and sets in Ruby. In this topic, we will explore common methods used with arrays and hashes. Mastering these methods will enable you to manipulate and work with data structures more efficiently. ### Common Array Methods Arrays are a fundamental data structure in Ruby, and using the right methods can save you time and improve your code's readability. Here are some common array methods: #### 1. `push` and `pop` The `push` method appends one or more elements to the end of an array, while the `pop` method removes the last element from an array. ```ruby # Example usage: my_array = [1, 2, 3] my_array.push(4, 5) # my_array now becomes [1, 2, 3, 4, 5] my_array.pop # my_array now becomes [1, 2, 3, 4] puts my_array # Output: [1, 2, 3, 4] ``` #### 2. `shift` and `unshift` The `shift` method removes the first element from an array, while the `unshift` method adds one or more elements to the beginning of an array. ```ruby # Example usage: my_array = [1, 2, 3] my_array.shift # my_array now becomes [2, 3] my_array.unshift(0) # my_array now becomes [0, 2, 3] puts my_array # Output: [0, 2, 3] ``` #### 3. `join` The `join` method concatenates all elements in an array into a single string. ```ruby # Example usage: my_array = ['apple', 'banana', 'cherry'] puts my_array.join(', ') # Output: apple, banana, cherry ``` #### 4. `reverse` The `reverse` method returns a new array with the elements in reverse order. ```ruby # Example usage: my_array = [1, 2, 3] puts my_array.reverse # Output: [3, 2, 1] ``` #### 5. `sort` The `sort` method returns a new array with the elements sorted in ascending order. ```ruby # Example usage: my_array = [3, 2, 1] puts my_array.sort # Output: [1, 2, 3] ``` ### Common Hash Methods Hashes are another essential data structure in Ruby, and using the right methods can make working with data more efficient. Here are some common hash methods: #### 1. `keys` and `values` The `keys` method returns an array of keys in a hash, while the `values` method returns an array of values. ```ruby # Example usage: my_hash = {a: 1, b: 2, c: 3} puts my_hash.keys # Output: [:a, :b, :c] puts my_hash.values # Output: [1, 2, 3] ``` #### 2. `merge` The `merge` method returns a new hash with the key-value pairs from another hash. ```ruby # Example usage: my_hash = {a: 1, b: 2} other_hash = {c: 3, d: 4} puts my_hash.merge(other_hash) # Output: {:a=>1, :b=>2, :c=>3, :d=>4} ``` #### 3. `delete` The `delete` method removes a key-value pair from a hash. ```ruby # Example usage: my_hash = {a: 1, b: 2, c: 3} my_hash.delete(:b) puts my_hash # Output: {:a=>1, :c=>3} ``` #### 4. `each` The `each` method iterates over a hash, executing a block for each key-value pair. ```ruby # Example usage: my_hash = {a: 1, b: 2, c: 3} my_hash.each do |key, value| puts "#{key}: #{value}" end # Output: # a: 1 # b: 2 # c: 3 ``` ### Key Concepts * Arrays and hashes have various methods that can be used to manipulate and work with data. * Mastering these methods will enable you to write more efficient and readable code. * Practice using these methods to become more comfortable working with arrays and hashes. ### Practical Takeaways * Use `push` and `pop` to add and remove elements from an array. * Use `shift` and `unshift` to add and remove elements from the beginning of an array. * Use `join` to concatenate elements in an array into a single string. * Use `reverse` to return a new array with elements in reverse order. * Use `sort` to return a new array with elements sorted in ascending order. * Use `keys` and `values` to return arrays of keys and values from a hash. * Use `merge` to return a new hash with key-value pairs from another hash. * Use `delete` to remove a key-value pair from a hash. * Use `each` to iterate over a hash and execute a block for each key-value pair. ### Additional Resources * [Ruby Documentation: Array Methods](https://ruby-doc.com/core-2.7.1/Array.html) * [Ruby Documentation: Hash Methods](https://ruby-doc.com/core-2.7.1/Hash.html) ### Do you have any questions or need help? If you have any questions or need help with understanding any of the concepts or methods covered in this topic, please feel free to leave a comment below. What's next? We will cover reading from and writing to files in Ruby in the topic "Reading from and writing to files in Ruby" under the section "File Handling and Exception Management".