Ruby logic: standard checks
This course covers conditional logic in Ruby. It starts with the full if, elsif and else block and shows that every if is an expression with its own value. It then covers unless and why pairing it with else is discouraged. Next come the &&, || and ! operators, short-circuit evaluation and the precedence trap in the word versions and and or. It also presents case and when as an alternative to long elsif chains. It ends with a small access-control challenge.
What you'll learn
- ✓Writing if, elsif and else blocks and using them as expressions
- ✓Using unless as a guard clause and avoiding unless with else
- ✓Combining conditions with &&, || and !
- ✓How short-circuit evaluation makes the order of conditions matter
- ✓Why and and or bind more loosely than &&, || and assignment
- ✓Matching one value against ranges, classes and lists with case and when
if, elsif, else: the full shape
if as a trailing modifier showed up in Ruby: programmer happiness. Ruby methods & returns used full if/elsif/else blocks in classify and check_age without naming the shape. This course covers it fully: conditionals, &&, || and the standard checks every Ruby program relies on.
Read the full lesson free →Curriculum
7 lessonsif, elsif, else: the full shape
The complete if, elsif and else block, checked top to bottom, and why every if returns a value.
unless: the direct inverse of if
The block form of unless, its use as a guard clause, and why RuboCop discourages pairing it with else.
Combining conditions: &&, ||, and !
How &&, || and ! build compound conditions, with parentheses grouping them as in arithmetic.
Short-circuit evaluation: why order matters
Ruby stops evaluating once the result is certain, which makes guard-then-use patterns like user && user.name safe.
and / or: the word versions, and why they're different
Word operators and, or and not bind below assignment, so x = false or true leaves x false.
case / when: a cleaner alternative
Using case and when to check one value against ranges, classes or comma-separated lists, with the first match winning.
Putting it together: a small challenge
An access-control method combining a guard clause, short-circuiting and case, followed by an exercise to write it.