##Objectives
- Define a variable.
- Create and reassign variables.
- Define pass-by-value as it relates to variables.
Much like in math, variables are words or characters that hold values. In algebra, however, variables are only placeholders for numbers. In Ruby, a variable can point to almost any type of value including numbers, strings, arrays, and hashes.
Variables are assigned values using = ("equal sign"), called the assignment operator. Variable names are typically all lower case and, in the case of multiple words, the words are separated by underscores.
current_president = "Barack Obama"
puts "In 2014, the president was #{current_president}."The code above will print In 2014, the president was Barack Obama..
Note: The syntax of
#{current_president}simply injects the value of the variablecurrent_presidentinto the string. This is called Interpolation and we'll cover it later -- but think of it as"In 2014, the president was" + current_presidentwhere you are adding that value to a string.
Now the variable current_president is equal to the string Barack Obama. Let's say somehow Stephen Colbert got elected as president for 2016. To update current_president, you would just reassign the variable much in the same way that you first defined it:
current_president = "Barack Obama"
puts "In 2014, the president was #{current_president}."
current_president = "Stephen Colbert"
puts "Now, it being the year 2016, the president is #{current_president}."This will print out:
In 2014, the president was Barack Obama.
Now, it being the year 2016, the president is Stephen Colbert.
Within this repository is a file named variables.rb with some examples you can read and play with. Download the Source Files for this lesson to see how it behaves.
'This is data, it is a string. Strings start and end with " '
"Part of being data, or a string, is that ruby doesn't interpret it."
puts 1+1
puts "1+1"
example = "The word 'example' is equal to this sentence, it's a named variable."
puts example
puts example
puts example
puts "variables are any previously undefined word that"
puts "starts with a lowercase letter."Running this file will print:
2
1+1
The word 'example' is equal to this sentence, it's a named variable.
The word 'example' is equal to this sentence, it's a named variable.
The word 'example' is equal to this sentence, it's a named variable.
variables are any previously undefined word that
starts with a lowercase letter.