Accessing and setting values in Ruby

Introduction

We use accessing and setting values to get or change information stored in variables or data structures.

When you want to read a value stored in a variable or container.

When you need to update or change a value in a list or hash.

When you want to check what is inside a data structure before using it.

When you want to save new information into a variable or data structure.

When you want to keep track of changes in your program's data.

Syntax

Ruby

# Accessing a value
value = container[key]

# Setting a value
container[key] = new_value

In Ruby, you use square brackets [] to get or set values in arrays and hashes.

For variables, just use the variable name to access or assign a value.

Examples

This gets the value at index 1 (second item) from the array.

Ruby

arr = [10, 20, 30]
puts arr[1]  # Accessing the second element

This changes the third item in the array to 50.

Ruby

arr = [10, 20, 30]
arr[2] = 50  # Setting the third element
puts arr.inspect

This gets the value for the key "name" from the hash.

Ruby

h = {"name" => "Alice", "age" => 25}
puts h["name"]  # Accessing value by key

This updates the "age" key to 26 in the hash.

Ruby

h = {"name" => "Alice", "age" => 25}
h["age"] = 26  # Setting a new value for key
puts h.inspect

Sample Program

This program shows how to get and change values in an array and a hash.

Ruby

arr = [5, 10, 15]
puts "Original array: #{arr.inspect}"

# Access the first element
first = arr[0]
puts "First element: #{first}"

# Change the second element
arr[1] = 20
puts "Updated array: #{arr.inspect}"

# Using a hash
person = {"name" => "Bob", "city" => "NY"}
puts "Original hash: #{person}"

# Access name
puts "Name: #{person["name"]}"

# Set new city
person["city"] = "LA"
puts "Updated hash: #{person}"

Important Notes

Remember, array indexes start at 0 in Ruby.

When setting a value, if the key or index does not exist, Ruby will add it (for hashes) or expand the array.

Summary

Use square brackets [] to access or set values in arrays and hashes.

Accessing means reading a value; setting means changing or adding a value.

Indexes in arrays start at zero, keys in hashes can be strings or symbols.