How to create an array in Ruby

How to create an array in Ruby: 1. Use the array command and assignment operator to create an empty array; 2. Use array literals to store known information; 3. Use the index operator to access each variable.

The operating environment of this article: Windows 7 system, Ruby version 3.0.0, Dell G3 computer.

In Ruby, it is a very common thing to store variables in variables, often called "data structures". There are many types of data structures, the simplest of which is an array.

Programs often need to manage variable collections. For example, a program that manages a calendar must have a list of days of the week. Each day must be stored in a variable, a list of them can be stored in an array variable. Through this array variable you can access each day.

Creating an Empty Array

You can create an empty array by creating a new array object and storing it in a variable. This array will be empty; you must fill it with other variables to use it. This is a common way to create a variable if you want to read a list of contents from the keyboard or a file.

In the following sample program, use the array command and assignment operator to create an empty array. Three strings (ordered sequences of characters) are read from the keyboard and "pushed" or added to the end of the array.

#!/usr/bin/env ruby
array = Array.new
3.times do
str = gets.chomp
array.push str
end

Using array literals to store known information

Another use for arrays is to store a list of things that are already known when writing a program, such as the days of the week. To store the days of the week in an array, you can create an empty array and append them to the array one after another like the previous example, but there is an easier way. Array literals can be used.

In programming, a "literal" is a variable type built into the language itself, which has a special syntax for creating it. For example, 3 is a numeric literal, and "Ruby" is a string literal. An array literal is a comma-separated list of variables enclosed in square brackets, such as [1,2,3]. Note that variables of any type can be stored in arrays, including variables of different types in the same array.

The following example program creates an array containing the days of the week and prints it. Use array literals and print them using each loop. Note that each of these are not built-in to the Ruby language, but are functions of array variables.

#!/usr/bin/env ruby
days = [ "Monday",
"Tuesday",
"Wednesday",
"Thursday",
"Friday",
"Saturday",
"Sunday"
]
days.each do|d|
puts d
end

Use the index operator to access individual variables

In addition to simply looping over the array (checking each individual variable in order), you can also use index Operator accesses individual variables from an array. The index operator will take a number and retrieve a variable from the array whose position in the array matches that number. Index numbers start at 0, so the first variable in the array has index 0.

For example, to retrieve the first variable from the array, you can use array[0], and to retrieve the second variable, you can use array[1]. In the following example, the list of names is stored in an array and retrieved and printed using the index operator. The index operator can also be used in combination with the assignment operator to change the value of a variable in an array.

#!/usr/bin/env ruby
names = [ "Bob", "Jim",
"Joe", "Susan" ]
puts names[0] # Bob
puts names[2] # Joe
# Change Jim to Billy
names[1] = "Billy"

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