That’s what you’re going to learn in this article!
How to Print Without A Newline
When you want to print something on the screen for the user to see, you normally use puts.
Like this:
puts "Hello there!"
Puts automatically adds a new line at the end of your message every time you use it.
If you don’t want a newline, then use print.
Example:
print 123
The next time you print something it will be one the same line as your last message.
Example:
print 123
print 456
print 789
123456789
But if you use puts:
puts 123
puts 456
puts 789
123
456
789
Every message has its own line!
Puts also treats arrays in a different way.
Example:
puts [1,2]
1
2
print [1,2]
[1,2]
Here’s another difference:
Puts attempts to convert everything into a string (by calling to_s).
Why is that important?
Because if you’re trying to puts an array with nil values…
It’s going to show some blanks lines!
Example:
puts [1,nil,nil,2]
1
2
To summarize, puts & print:
Convert things to strings, even if that means an empty string
Only puts:
Adds a new line to the end of your messages
Displays array elements one-per-line
Debug Output With P
What about puts vs p?
p is a method that shows a more “raw” version of an object.
For example:
> puts "Ruby Is Cool"
Ruby Is Cool
> p "Ruby Is Cool"
"Ruby Is Cool"
What is p useful for?
Debugging.
When you’re looking for things like (normally invisible) newline characters, or you want to make sure some value is correct, then you use p.
Another difference:
puts always returns nil
p returns the object you pass to it
This is a more technical difference…
But it can show up if you try to puts a variable as the last line of a method, and you’re using the return value of that method.
Example:
def numbers
puts 123
end
numbers
# nil
In this example, the numbers method will display 123 on the screen, but its return value will be nil.
If you try:
result = numbers
Then result will be nil, instead of 123.
But if you use p then it will work.
Pretty Printing
Ruby has yet another printing method.
Called pp.
This is like p, but it prints big hashes & arrays in a nicer way.
Note that older version of Ruby (pre 2.4) need to do require 'pp' to get access to this method.
Video Tutorial
Summary
You’ve learned about the differences between puts, print & p in Ruby!
Now it’s practice time.
If you practice with something new immediately you’ll integrate this information into your knowledge base, if you don’t practice you’ll forget & you’ll not make progress.
Related
2 comments
Tokara says
4 years ago
I really like how you focus on the basics, which is very important. Other people who write articles on Ruby try to get fancy and showcase something that is complicated, but rarely used or isn’t practical.
