FAQ: Data Structures - (Re)Introduction to Iteration

This community-built FAQ covers the “(Re)Introduction to Iteration” exercise from the lesson “Data Structures”.

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Beginner question.
Could I get a clarification about Hashes and especially placeholder symbol |x, y| in the below example?
Especially this line,
family.each { |x, y| puts “#{x}: #{y}”

I’m very confused about how the placeholder section |x, y| is laid out. I can understand what it means but it seems kind of “wrong”, therefore I think my mental model of it must be wrong too.

I’ve understood the key-value pain to be very, very similar to an index number and a value that number would refer to.
eg. say,
variable = “igloo”, var[1] index location would refer to value “g” (as index starts a 0).

Well I’m extremely confused about why in the placeholder text you’d refer to |x, y|. That’s almost as if you be using |the location of a value, and the value itself|.
Was this just an improvised answer because both the value and location was useful, eg Homer, and Dad, or is the |x, y| format to refer to |hash location, value| something we’ll use again and again. Thanks.
Sorry if I was confusing. I’m an extreme newbie with any coding language and only less than a week into my Ruby study.

friends = [“Milhouse”, “Ralph”, “Nelson”, “Otto”]

family = { “Homer” => “dad”,
“Marge” => “mom”,
“Lisa” => “sister”,
“Maggie” => “sister”,
“Abe” => “grandpa”,
“Santa’s Little Helper” => “dog”
}

friends.each { |x| puts “#{x}” }
family.each { |x, y| puts “#{x}: #{y}” }

1 Like

I also have the same question about "{ |x| puts “#{x}” }
I saw it in the previous exercise and that part was not explained at all.

When we iterate over an array or hash with .each the index isn’t used. .each just returns each element in an array or each key => value pair in a hash.

friends.each {|x| puts "#{x}"} #iterating over the friends array
#.each returns each element 1 at a time. x is the temporary placeholder for 
#the element. Whatever code is included in the code block can access the element
#referred to by x
family.each { |x, y| puts "#{x}: #{y}" } #iterating over the family hash
#x is the placeholder for the key. y is the placeholder for the value

Hope this helps.

2 Likes

Yes, it does. Thank you!

1 Like