--- title: Ruby array transform question from reddit slug: ruby-array-transform-question-from-reddit published_at: 2021-07-03 13:32:10 +0000 updated_at: 2026-03-04 20:14:06 +0000 summary: description: https://www.reddit.com/r/rubyonrails/comments/oc96dt/hello_i_need_help_to_change_this_array_of_objects/ The question: https://gist.github.com/cjavdev/7bafa99f8eb0517fd1711f1e870130db A solution: https://replit.com/@CJAvilla/array-fun#main.rb tags: [] views: 168 author: CJ Avilla url: https://www.cjav.dev/videos/ruby-array-transform-question-from-reddit youtube_url: https://www.youtube.com/watch?v=v6jYFGsEmZQ youtube_id: v6jYFGsEmZQ embed_url: https://www.youtube.com/embed/v6jYFGsEmZQ thumbnail_url: https://i.ytimg.com/vi/v6jYFGsEmZQ/hqdefault.jpg type: video --- # Ruby array transform question from reddit *Published: July 03, 2021* *Views: 168* ## Watch [Watch on YouTube](https://www.youtube.com/watch?v=v6jYFGsEmZQ) [![Ruby array transform question from reddit](https://i.ytimg.com/vi/v6jYFGsEmZQ/hqdefault.jpg)](https://www.youtube.com/watch?v=v6jYFGsEmZQ) ## Description https://www.reddit.com/r/rubyonrails/comments/oc96dt/hello_i_need_help_to_change_this_array_of_objects/ The question: https://gist.github.com/cjavdev/7bafa99f8eb0517fd1711f1e870130db A solution: https://replit.com/@CJAvilla/array-fun#main.rb ## Transcript hey what's up um i'm in a coffee shop so sorry if the noise is wack or whatever but i wanted to just go through the process of um taking the input of this and then trying to solve it so that you get the output um just so that you can see how i would think about it so i'm just going to copy the input array here and i'm using replit and i'll share the result on reddit here in a little bit um so the first thing i'm going to do is clean this up so it's like valid some valid ruby code here i'm going to make these strings i think these are all missing quotes around them so when you're in replit you can just hold command and then click a bunch of places so that should give us a bunch of strings and then i'm just going to kind of like clean up the formatting here um okay so that's our first item and then our second item is here i'm in the starbucks it's kind of crazy there's like wild thunder and lightning outside it doesn't usually thunder and lightning here but today it has decided to rain like crazy and fender lightning so fun all right so i think this is pretty close to what we want that needs to be indented there and then let's just call this our input array and i think that needs a closing bracket i would probably also like put these on the same line here uh style is whatever but it does help if you have like something nice to look at um when you're trying to reason about it so if i say run i should see oh let's do a p output or input here and say run we should see it over here on the right hand side hopefully this is big enough for you to see so that's basically the raw input okay so the way that i would think about this is we want to take the items or we want to iterate over each of these items that are sort of in the input each item has an id but we don't care about the id what we care about is collecting up these sub items that are part of each of this i this like top level parent item if the product box id is the same so in this case we have an input with three elements in our array but this first element and the second element sorry need to be merged because um the product box is the same and so in the resulting array we should have two items here or two elements in our items array and then these two which should be merged we should have a third one that is separate because the product box is separate so what i want to do is i'm going to collect these into a result that's going to be an array and then at the end we'll just p the result now in practice i would probably write like a test for this with our spec but for now we can just use we're using wrap up so we can share it easily and test it as we go so i want to go over the input so i'm going to say input dot each do item an item is probably a bad name because we're going to be also reaching into these items so maybe we say uh i don't know what this actually is so we'll just call it item for now now the very first thing we need to know about every single item is what its product box id is so i'm gonna say product box id and we want to grab that from the item and so we can do that by reaching into the items and i'm just going to assume that because the input only has one item in this sub items array that i can say something like item items dot first and give me the product box and that should give me the product box id i'm gonna test it as we go so i'm gonna print out product box id here and i see i should see one one and two that's right because i'm seeing the product boxes one one and two so that's right now the next thing we want to do is we want to say like if the result already contains an item where the product box is product box id then add the sub items to that array otherwise just add item to result okay so that's kind of like my thinking and so we actually need to like iterate over all of the results and see if we can match the product box id with anything that's already in the result right now the result's empty but as we go through this loop we're going to be adding stuff to that result so we can say result.each do these result item okay we want to say if the result items items.first product box is equal to product box id that's going to give us that that's going to give us a match right and if it's a match then maybe we just store off that result item and then we'll handle we'll handle this sort of if statement in a second so i'm going to cut that drop it down here and let's just say that we have like a result um found is nils we'll start off with the nil result and then inside of this inside of this condition if we meet this condition then we found an item in the results so we can say result found is equal to result item because that's the one where the product box matches and we can say break because i think that should break us out of the each loop um but that actually doesn't matter because it can it can continue iterating that's totally fine uh and so here we should have p result found let's just see if we're able to find one actually no we won't even be able to find one until we start adding to it so um so now we need to start adding results so now we want to say like uh if result found dot nil so if it's nil that means we didn't find any of the results that match that product box id and in that case we want to add two results so we can say results we're going to add in the original item that we're iterating over otherwise we need to instead of adding two results we want to add to the result found so if if we did find a result in the existing result array then we should be able to go into items first or items and then just actually add this uh the first item in the parent item right so item.items.first should be like this subarray so we want to add this to the result found subarray hopefully this works okay undefined local variable or method on line 39 so i go to 39 results uh i called it results so i'm just going to change this all to results say run undefined method result on line 30. ah gosh okay so this one needs to be results also okay so i think this is what you're looking for so let's just take a look so we should only have two things here so we have id3 and there is one item there two items there and then that's the end of the first id3 and then the second id3 has this different with the product box too so i think that matches exactly what you were going for in the result and yeah hopefully this explanation helps i noticed there was another answer down here using inject which is also totally valid um and is another approach uh but i yeah just wanted to kind of like walk through step by step using a lot of these like sort of more primitive tools to show you how that works i'll also share this uh in a second on reddit so hopefully that helps and uh yeah thanks for the question i guess um yeah and i'm sure there's like way better like more clever ways to do this but hopefully this will get it working cheers --- [Back to all videos](https://www.cjav.dev/videos) --- ## Hey Agent, thanks for visiting! 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