I saw several posts on sorting an array that is a value of a hash, but I'm trying to sort an array of arrays that is a value of a hash. I have a hash that looks like this:
h = {
"pets"=>[["dog", 1], ["cat", 2]],
"fruits"=>[["orange", 1], ["apple", 2]]
}
I would like to sort array of arrays according to the first elements (string) of the arrays inside. So I want the result to be
{
"pets"=>[["cat", 2], ["dog", 1]],
"fruits"=>[["apple", 2], ["orange", 1]]
}
This is what I have right now:
h.map do |key, value|
value.sort_by! { |x, y| x[0] <=> y[0] }
end
But this just returns the original array. What do I need to change? Thanks!
The one issue I see is that you are attempting to map your hash. That will always return an array.
In this case, you’ll get back something like this: [[["cat", 2], ["dog", 1]], [["apple", 2], ["orange", 1]]]
If you want to modify your hash in place, you can do:
h.each { |key, value| h[key] = value.sort_by { ... } }
Then h will be the new hash, sorted as you expect. Or you can set it to another variable:
new_hash = h.each { |key, value| value.sort_by! { ... } }
Next, it looks like you’ve confused sort and sort_by. (Easy to do) When you use sort, the two variables you pass in your block are assigned to the values being compared. (In your case, the arrays ["dog", 1] is one argument, and the other would be another array to compare it to, like ["cat", 2]) However, sort_by expects you to do the computing to determine where it’s place is in the new order. Normally sort_by only accepts a single argument, but because you’re working with arrays (and because of the way Ruby handles tuples) when you tell sort_by to accept 2 arguments (x and y) those are set to the first and second values of your array. (x == "dog", y == 1)
So you’ve got 2 options here: Keep your block the same and switch your enumerable method to sort, or switch to sort_by and change your block:
sort:
h.each { |key, value| h[key] = value.sort! { |x, y| x[0] <=> y[0] } }
sort_by:
h.each { |key, value| h[key] = value.sort_by! { |x, y| y } } # In this case, `y` is the second value in your arrays, which is the integer
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