Assigning to Variables in Ruby

Assigning to Variables in Ruby: Types of Assignment

We have different types of ways by which assigning to variables in Ruby is done.

Assignment

In Ruby, the assignment uses the = (equals sign) character. This example assigns the number seven to the local variable a:

a=7

A local variable is created by the assignment if the variable was not referenced previously.

Abbreviated Assignment

We can mix several of the operators and assignments. To add 2 to an object we can write:

b = 1

b += 2

This is equivalent to:

b = 1

b = b + 2

We can use these operators this way: +, -, *, /, %, **, &, |, ^, <<, >>

There are also the operators ||= and &&=. If the value was nil or false, the former makes an assignment, while the latter makes an assignment if the value was not nil or false.

Consider the following example:

b ||= 0

b &&= 1

These two operators behave more similar to b || b = 0 than b = b || 0.

Multiple Assignment

On the right-hand side, we can assign numerous values to multiple variables in Ruby:

c, d = 1, 2

puts"c=#{c}, d=#{d}"

Output

c=1, d=2

We can use multiple assignments to swap two values:

old_value = 1

new_value=2

new_value, old_value = old_value, new_value

puts"new_value= #{new_value}, old_value= #{old_value}"

Output

new_value=1, old_value=2

If you have more values on the right-hand side of the assignment than variables on the left-hand side, the extra values are ignored:

a, b = 1, 2, 3

puts"a=#{a}, b=#{b}"

Output

a=1, b=2

We can use * to gather extra values on the right-hand side of the assignment.

a, *b = 1, 3, 4

puts"a=#{a}, b=#{b}"

Output

a=1, b=[3, 4]

The * can appear anywhere on the left-hand side:

*c, d = 3, 4, 5

puts"c=#{c}, d=#{d}"

Output

c= [3, 4], d=5

But we only use one * in an assignment.

Array Decomposition

You can dissect an Array during assignment using parenthesis, just like you do with method arguments:

(c, d) = [1, 2]

puts"c=#{c}, d=#{d}"

Output

c=1, d=2

As part of a broader multiple assignments, you can decompose an Array:

a, (b, c) = 1, [2, 3]

puts"a=#{a}, b=#{b}, c=#{c}"

Output

a=1, b=2, c=3

Because each decomposition is treated as a separate multiple assignment, you can use the * symbol to collect arguments in the decomposition:

a, (b, *c), *d = 1, [2, 3, 4], 5, 6

puts"a=#{a}, b=#{b}, c=#{c}, d=#{d}"

Output

a=1, b=2, c=[3, 4], d=[5, 6]

Frequently Asked Questions

How is assigning to variables in Ruby done?

Local variables in Ruby begin with the letter or a lowercase letter. A local variable's scope extends from the opening brace of a block to its closing brace, or from class, module, def, or do to the equivalent end.

What does @variable mean in Ruby?

In Ruby, the at-sign ( @ ) before a variable name (e.g. @variable_name ) is used to create a class instance variable.

What does || mean in Ruby?

The or-equals operator in Ruby lets you assign a value to a variable if and only if that variable evaluates to nil or false. ||= is the operator that accomplishes this. This operator has two pipes that indicate or and an equals sign that represents assigning a value.

What are the four types of variable scope in Ruby?

Ruby has four types of variable scope, local, global, instance and class. In addition, Ruby has one constant type. Each variable type is declared by using a special character at the start of the variable name as outlined in the following table.

Conclusion

In this article, we have extensively discussed the various ways of assigning to variables in Ruby. We began with a brief introduction to variables followed by an explanation and examples of assigning to variables in Ruby.

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