--- title: Modeling Attachments and using Counter Caches - CreatorPlatform.xyz - Part 22 slug: modeling-attachments-and-using-counter-caches-creatorplatform-xyz-part-22 published_at: 2022-09-27 10:30:02 +0000 updated_at: 2026-03-04 20:13:07 +0000 summary: description: Playlist: https://www.youtube.com/playlist?list=PLS6F722u-R6IJfBrIRx3a2SBkAL4vUp2p Code: https://github.com/cjavdev/creators.dev/ Follow me on Twitter: http://twitter.com/cjav_dev #rubyonrails #ruby #rails tags: [cjav_dev, web development tutorials, web development for beginners, vim, ruby, rails, javascript, ruby on rails, active record, ruby on rails tutorial] views: 328 author: CJ Avilla url: https://www.cjav.dev/videos/modeling-attachments-and-using-counter-caches-creatorplatform-xyz-part-22 youtube_url: https://www.youtube.com/watch?v=sFSprEVFhc4 youtube_id: sFSprEVFhc4 embed_url: https://www.youtube.com/embed/sFSprEVFhc4 thumbnail_url: https://i.ytimg.com/vi/sFSprEVFhc4/hqdefault.jpg type: video --- # Modeling Attachments and using Counter Caches - CreatorPlatform.xyz - Part 22 *Published: September 27, 2022* *Views: 328* ## Watch [Watch on YouTube](https://www.youtube.com/watch?v=sFSprEVFhc4) [![Modeling Attachments and using Counter Caches - CreatorPlatform.xyz - Part 22](https://i.ytimg.com/vi/sFSprEVFhc4/hqdefault.jpg)](https://www.youtube.com/watch?v=sFSprEVFhc4) ## Description Playlist: https://www.youtube.com/playlist?list=PLS6F722u-R6IJfBrIRx3a2SBkAL4vUp2p Code: https://github.com/cjavdev/creators.dev/ Follow me on Twitter: http://twitter.com/cjav_dev #rubyonrails #ruby #rails ## Transcript hey what's up welcome back in this episode you're going to see how to add attachments to our products we're going to use the same file uploading structure but we're going to also take a look at counter caches which is a nice feature of ruby on rails and so let's get into it the vision is we want to take this internal product show page which has kind of been a dumping ground for a bunch of test stuff we have a bunch of images here this checkout button all of it's got to go what i want to do is add a table that will list out all the different attachments that are available when a customer buys this product and so we're going to start with maybe just jumping over here and grabbing a table here an html table and now let's open up that product show page and we're going to remove that thumb we're going to remove the button and we'll just dump that table in there and this is going to be our attachments so this is going to be a list of all the attachments that customers have access to when they buy this product or when they buy and then the name of the product okay so now if we come back over here refresh the page now we can see this table of attachments but i kind of want to move it so that it fits better also i spelled attachments wrong i think it's like yeah it's this here that's a that is a tuffy okay so attachments okay now we also want to do something here where we're gonna add maybe this header and again we're going to add attachments and let's also add a div with class flex so that we can have the image on the left and then the table on the right so we'll wrap this in a div and then we'll say this is going to be flex auto so the table has as much space as it wants to grow okay let's come back over here take another look all right looking pretty good looking pretty good instead of attachments what am i doing we want this to be the product name okay so this should be the product name and then above all of this we want some like margin top probably eight or so just so there's okay now we have these attachments we have this add user button none of the content of the table makes any sense because we don't actually have the concept of attachments in the database yet let's jump into the terminal and add some models rails g model attachment and an attachment is going to have a file but that's going to be added with active storage so we don't actually need anything in the database for it but we will want the attachment to be related to a product so that's going to be a product references we also maybe want to give a name to an attachment i'm not sure and then here is where we're going to start thinking about what we want to do with these attachments every time an end customer downloads an attachment i think we want to increment a counter or keep track of that now one way we could do that is have a separate table called attachment views and if we want to know how many times has this attachment been downloaded we could do a query that does a a join on the attachment views table and groups by the attachment and then gives us a count however there is a way in rails a to add a denormalized field called a counter cache so here we might say something like views count or something and make this an integer and the data in this field is going to be the count of how many related objects there are and that is just a simple sort of optimization trick that you can do to improve performance all right so that attachment looks good let's also generate a new model called an attachment view an attachment view is going to be re like related directly again to an attachment references and it's also going to be related to a customer and the attachment view let's see it's also going to have some date times or time stamps or whatever but that's fine one thing we could also potentially use an attachment view for is limiting how many times someone downloads something so if you wanted to say add some restriction later down the road where you said okay you can download this book up to three times after you've downloaded it the third time things get a little fishy you're probably not reading an ebook i don't know maybe 10 more than 10 times right okay let's open up the well first let's migrate the database railsdb migrate and boom okay that looks great let's open up the attachment here and so the attachment belongs to a product and it has many attachment views okay yeah sure and the attachment view belongs to an attachment here's where we can say counter cache now by default if our field on the attachment was called attachment views count then we could just say counter cache true but because we're using a name that's a little bit shorter we're just saying views count instead of attachment views count we have to specify the name so this should work let's open up the rails console and we're going to create a new attachment so we'll say attachment.create product is product.last and let's see okay so now we can say attachment view dot create is attach uh dot create attachment is attachment last and customer is customer.last okay so that created the new attachment view now look at the sql that executed as we were running this so first we see this insert into the attachment views totally expected we see these every single time we work with active record right like here's our insert into attachments this was us adding data into the attachments table but this is new this update attachments set the view counts this is where we're denormalizing and caching the count for the related object so this is a really cool feature of rails it's called counter cache so if you encounter that later if you encounter it later uh yeah that's a that's a good one all right so now we have the uh the data in the database or we at least have a shape of the data in the database let's let's create a controller for managing the attachments internally so we're going to have an attachments controller and i think the form is going to live on that product show page so this will just need to have like the create actions so now let's go to the attachments controller before action um authenticate the user and then we're gonna have this create method we're gonna have a private thing going on attachment params and those are gonna require the file and also a name right so we need to go to the attachment and say this has one attached file in in terms of the routing for this i think what we might want to do is nest the create underneath so we can talk a little bit about nested routing right so if we go to the routes file here right now we have products we could do say do resources attachments that way our routes are going to be nested for attachments underneath products this is going to give us something like slash products slash attachments as our create route so let's let's add that and we'll come over here and say we'll just put some nonsense in here and now we can see what the attachment routes look like okay so now we have these routes so the actual url path is going to be all nested under products slash the id of the product and then slash attachments now you'll also notice that here it's still nested under products slash product id attachment id but if you have the id of the attachment you probably don't need to know what product it's related to and so some people would say rather than having it nest so deeply what you could do is instead design your api so that you only have these top level attachments routes when they need to be related to a specific product and then any other time if you have the id of the object for instance for a show page update or delete you would move uh this down to its own proper sort of top level thing like attachment slash id and there is a feature for that and i think it's so i think we can say shallow true so now if we refresh our routes here and go to attachments now you'll see that all of the attachment paths that are related to a specific attachment now are un they're unnested from product because we already know what product they're related to if we've already created the attachment so anyways i think that's how we might want to line this up and now we can jump over to products and let's look at a specific product okay so these are going to be the the attachments that we want to add so let's go to our attachments controller again and we're going to say product is currentuser.products.find params product id so when we're looking again let's look at these routes one last time so instead of params id like this this colon id here is called a dynamic segment that's like a part of the path that will become a key in the params hash that's available inside the controllers most of the time we say params like attachment.find params id that's because by default this is always called id when we're looking at a nested route this is called product id so we're going to see params product id and that's where the id of the product is going to sit and that's how we can find the product so now we're going to be able to say something like attachment is product.attachments.create attachment params and then if it was saved uh let's see or yeah if at attachment.save so here we can just actually make this new if it was saved then we want to redirect to the product path otherwise flash flash the errors so actually if it's if it was not saved then we'll flash errors and then in either case we'll redirect back to the product path what i think we might want to do is actually use turbo here so let's take a look at that in a minute okay so and that's just because we're going to be on the same page okay all right let's go back to our products and we want to edit a specific product okay so now we have all these attachments um let's update this view so that we can iterate so uh product show that we're actually iterating over the attachments so product attachments that each do attachment okay and this is going to have the name attachment.name and then we'll probably have a link to download it or something just so that yeah the end the user can actually download their own file undefined method attachments for product so we didn't set up that association yet so a product has many attachments okay all right so now we have some list of attachments let's remove this add user button and let's start working on a form at the bottom of this view so this is going to be a form where the action is going to go to um attachment or is it called product attachment this is going to be products attachment path okay and the method is post all right let's go over to tailwind ui and grab some components for working with forms again form layouts stacked i like the stacked one okay so really we just need an input box and a in fact because we just need an input box and a name let's just copy a simple input box here and the instead of email we're gonna have the name and this is gonna have uh attachment name we're also gonna have a file input so we already talked about file uploading in a previous episode and so over on the product new page we actually have a file input and this is where we talked about the direct upload url and we already set up active storage so if you missed that episode head over and take a look at how that works so this here we actually just want to change the name to attachment file and all right that should be good now we need to add a button come back over grab a trusty button this is type submit and add attachment okay now if we refresh our page over here products slash 30 31. product attachments path right okay so when you have a path that re has a dynamic segment like the one we talked about you have to pass in um an argument to populate that id all right so here's our form it's down below we actually want this inside of the same sort of column as our attachments table uh not like that okay boom okay that's looking pretty good um this input box does not actually look how i expected it to look though so i think something must be missing here um the name okay also this form i think we want to give this some we might even want to use like a divider or something between the form and the end of the table um but okay so this input is not looking how i expected it input type this should be text okay all right there we go that looks much nicer all right so let's just say this is like the ebook or something and then we can say choose file and we're just going to put in an image i know uh add attachment wow look at that okay it's already it's already working so now we can say i don't know this is the audio book and we can choose a file and uh i guess we're going to open the same file that attachment okay now the audiobook is there so that is super cool we've got our form it's adding attachments and i think that is in a good spot so um right now i don't know if the files are actually being saved on those attachments let's open up the rails console once more and say attachment dot last dot file okay so it has a file it looks like this is an audio book and if we wanted to say dot url okay we've got this url we should be able to open this up and it brings us to aws where we can download it fantastic all right let's make our form just a little bit nicer all right let's also add the count of how many views the attachment has seen since the beginning and so we can add that here attachment dot views count and we'll just add another thing here this is going to be called views and now we'll refresh and so our first attachment that we were playing with in the console has one view that's great so let's let's wrap it up there thanks so much for watching in the next episode we've got a lot more to build so we're going to keep keep at it so thanks thanks again and we will see you in the next one [Music] --- [Back to all videos](https://www.cjav.dev/videos) --- ## Hey Agent, thanks for visiting! 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