How to Create a Ruby Block Consisting of Multiple Lines?

If you're just starting with Ruby, then you may have seen blocks with curly braces ({...}) added on a single line (next to methods), for example, like so:

array.inject(0) { | sum, n | sum + n }

These blocks can easily be split into multiple lines, for example, to make the code more readable when additional statements are added:

numbers = [1, 2, 3, 4, 5]

numbers.inject(0) { | sum, n |
    puts "#{sum} + #{n} = #{sum + n}"
    sum + n
}

#=> 0 + 1 = 1
#=> 1 + 2 = 3
#=> 3 + 3 = 6
#=> 6 + 4 = 10
#=> 10 + 5 = 15

However, the general convention is to use the do...end syntax for multi-line blocks (and curly braces for single line blocks):

numbers = [1, 2, 3, 4, 5]

numbers.inject(0) do | sum, n |
    puts "#{sum} + #{n} = #{sum + n}"
    sum + n
end

#=> 0 + 1 = 1
#=> 1 + 2 = 3
#=> 3 + 3 = 6
#=> 6 + 4 = 10
#=> 10 + 5 = 15

Please note that blocks with curly braces ({...}) have a higher precedence than the do...end syntax.