Sometimes you might want to create an “if not” statement. You can use the if-statement to do this, but another option is using the “unless” statement instead. That’s because the unless-statement can be a little easier to read.
Here’s an example:
weight = 90 unless weight < 85 puts "you are overweight, so you need to go on a diet and have plenty of exercise" end
You should read this statement, as "do whatever is inside the block, unless weight is less than 85".
This will output:
PS C:\temp\irb> ruby .\unless.rb you are overweight, so you need to go on a diet and have plenty of exercise PS C:\temp\irb>
You can also add an "else" clause into the unless statement, but it is best to avoid this since it can make the code a little difficult to follow.
With if-statements we saw how you could condense an if statement into a single line. We can do the same with the unless statement too, here's an example:
def fail_message puts "this is a failure" end def result false end fail_message unless result # this outputs: "this is a failure"