Alternative block syntaxes

Next to the syntax shown before, using do and end, Ruby comes with an alternative syntax, which uses curly braces for defining a block.

These two statements do exactly the same:

5.times do
  puts "Oh, hello!"

5.times { puts "hello!" }

Both statements define a block, which is passed to the method times. And both blocks contain a single line of code.

Blocks can be defined enclosing code in do and end, or curly braces {}.

So, when do you use one or the other syntax?

In the Ruby community there’s the convention to use curly braces if you have a single line block and it fits nicely on the same line (as, in our example, it does).

Whenever you need to have more than one line in your block, then you use the syntax using do and end. Sometimes people also use the do and end syntax when they feel it makes the code more readable.

Use curly braces {} for blocks, when the code fits on one line.