Assignment Operator
A solo = symbol is used for assignment in Ruby. It is also combined with many other operators for a compound operator that does the operation and then assigns the resulting value.
> food = :taco
=> :taco
> food
=> :taco
We might see assignment happen from a method call or block expression.
> squares = [1,2,3].map { |n| n * n }
=> [1, 4, 9]
> full_name = begin
first_name = "Bob"
last_name = "Burgers"
"#{first_name} #{last_name}"
end
=> "Bob Burgers"
Another common pattern in Ruby is a single-line if statement which can be combined with an assignment. The Ruby Docs have an example ↗ that demonstrates both this and the way that a variable declaration is hoisted to the top of the scope.
a = 0 if false # does not assign to a
p local_variables # prints [:a]
p a # prints nil
Abbreviated Assignment Operators
Then there are all the composite assignment operators like +=, -=, *=, /=, %=, **=, &=, |=, ^=, >>=, and <<=. The Ruby Docs call these Abbreviated Assignment Operators ↗.
Let's look at two equivalent statements:
> x = 5
=> 5
> x = x + 1
=> 6
> x = 5
=> 5
> x += 1
=> 6
These operators allow us to write terser code. While the += operator is probably showing up from time to time in our codebases, I bet we're rarely seeing many of these other ones.
> x = 11
=> 11
> x %= 3
=> 2
> x **= 4
=> 16
Conditional Assignment Operators
Related to the above are the two conditional assignment operators ||= and &&=. The ||= operator is fairly common in idiomatic Ruby code, whereas I'm hard-pressed to think of a time to use the &&= operator.
> x ||= 10
=> 10
> x &&= 20
=> nil
There are some good details on the ||= operator page, so be sure to check that out.