Question

Any thoughts on why the following code outputs the contents of the {bracket} code but not the “do” code?

my_array = ["alpha", "beta", "gamma"]
puts my_array.collect {
    |word|
    word.capitalize
}
puts "======================"
puts my_array.collect do |word| word.capitalize end
puts "=========END=========="

When executed the code returns the following as the output

Alpha
Beta
Gamma
======================
#<Enumerator:0x2517ed0>
======================

Any and all help appreciated.

Answer 1

do ... end and {} block syntaxes have different precedence – a block defined using braces binds tighter to its caller than one using do ... end, which is why your first example works as intended.

Edit: Elaborating a bit: When you use puts my_array.collect {|word| word.capitalize}, you’re sending to puts the result of my_array.collect {|word| word.capitalize} – the array resulting from capitalizing each item in the original array. When you use puts my_array.collect do |word| word.capitalize end, you’re passing the value of my_array.collect – an enumerator – to puts, and ALSO passing the block to puts. Since puts doesn’t yield to the block, you end up writing the string representation of your enumerator to $stdout, and the block never gets called. Ergo, it’s a good idea to use parenthesis when using blocks like this, unless you (and anyone you’re working on the code with!) knows exactly what’s happening.