--- title: Add Stock Prices to a Chart with Ruby on Rails slug: add-stock-prices-to-a-chart-with-ruby-on-rails published_at: 2021-04-12 17:00:17 +0000 updated_at: 2026-03-04 20:14:18 +0000 summary: description: Add Stock Prices to a highchart javascript chart with Ruby on Rails. #rails #rubyonrails tags: [Add Stock Prices to a Chart with Ruby on Rails, Ruby on Rails tutorial, API Controller, JavaScript Stock Charts, Stock Chart, JavaScript tutorial, ROR, Ruby, Rails] views: 1345 author: CJ Avilla url: https://www.cjav.dev/videos/add-stock-prices-to-a-chart-with-ruby-on-rails youtube_url: https://www.youtube.com/watch?v=tH7DbRgi6_A youtube_id: tH7DbRgi6_A embed_url: https://www.youtube.com/embed/tH7DbRgi6_A thumbnail_url: https://i.ytimg.com/vi/tH7DbRgi6_A/hqdefault.jpg type: video --- # Add Stock Prices to a Chart with Ruby on Rails *Published: April 12, 2021* *Views: 1345* ## Watch [Watch on YouTube](https://www.youtube.com/watch?v=tH7DbRgi6_A) [![Add Stock Prices to a Chart with Ruby on Rails](https://i.ytimg.com/vi/tH7DbRgi6_A/hqdefault.jpg)](https://www.youtube.com/watch?v=tH7DbRgi6_A) ## Description Add Stock Prices to a highchart javascript chart with Ruby on Rails. #rails #rubyonrails ## Transcript what's up everyone welcome back uh in the last episode we showed how to install high charts and am charts we did a little comparison of the onboarding process for both of those third-party libraries for rendering stock charts with javascript in this episode we're going to take some pricing data that we have ingested from alpha vantage and display it on this on a high chart graph so that we can see the price data for a company on on high charts so let's go through that process now so if you'll recall this is where we landed in the last episode we have a chart that has some price data and we have some flags this price data is just being loaded directly from a cdn provided by or like some sort of json link for some data that was provided by hi-chart for demo purposes and so what we're going to do is load this data instead of being from high charts we're going to load it from our own database um so the very first thing we want to do is create a new api endpoint for rendering back the json prices for a company now if we if we dig into and look at the data that's coming back so this is the cdn that is providing the data for high charts and if we look at this it is just an array of arrays where there's two elements in the array the first is a unix timestamp and the second is the price for that day and so that ends up showing us sort of this this data here this is actually like a usd to euros exchange rate that's on display as like the the demo data for high charts so we need to have an api endpoint that returns json similar to that so let's generate a new api controller so what i want to do is say rails g controller api slash and i think what we want to do is call it maybe prices and yeah so we'll just it'll just be like um a new prices controller inside of the api namespace and the reason i'm using api slash here is that i want the controller to be namespaced i want the route to be namespaced under api because users should never actually like visit this url instead it's going to be a a url that we hit purely for returning some json data that is not like human readable so let's take a look at what what this created so if we go to api prices controller you'll see that the the name of the controller is api colon colon and then prices controller i actually like to use api the api namespace so i'll use the module to wrap this inside of an api namespace and we'll just use the default application controller that's fine for now i do want to skip verifying authenticity i don't really care we're not going to be accepting post requests here anyways we're going to just say deaf show we'll have one endpoint it'll be a show route where we return the prices for a specific company let's actually make it an index route because it's technically returning several prices and the index route will require that a ticker is passed in or that some company information is passed in so i think it makes sense to pass in the ticker to make it easy but i wonder if we want to pass in the company id instead which would make it so that we couldn't really like easily reuse it outside of this app but i think i might like that because then random users won't hopefully won't be fetching prices directly from here so let's make it let's make it take in the id of a company and then return the prices for that company so let's just say company is equal to company dot find params id or maybe like params company id we will say render json for company dot prices and let's just see where that gets us so if we go to our routes file we need to add a new resource here for this prices controller and you'll notice that we have resources charts but in this case because it's going to be an api controller we want to say namespace namespace api do and then inside of this namespace we're going to put the prices controller okay so this is going to make it so that we can we can add an api prices endpoint that'll take in company id is equal to like one or something like that and that'll return the prices for company with id one so let's see how this works and if it's working so we'll say api slash prices company id equals one awesome wow that was like almost too easy right uh but we have a couple issues so number one is that like the data that's coming back here is in a format that is different from the data that we are expecting which is this array of arrays instead it's an object where the keys are dates and the values are prices and so in the prices over here are string values instead of decimals so we have a couple options one we could change the way that we're actually storing prices on the company object to just match what we expect here or we can build some sort of transform on the front end or on the back end or a combination of both and i think that the easiest thing here might be to actually just store them differently i'm trying to think about why we might want to store them like this right like there is a there are there's a slight benefit to storing it as a dictionary here where the key is the date and the value is the price because technically we could ask for the price on a specific day for a specific company so we could say hey for company number one give me back the price that it was on 2020 11 17 and we'd be able to index into the hash at that specific date and get back the price rather than needing to iterate to find that date so what i'm thinking is that it would be valuable to map to to convert these prices from this json format into this json format on the client right before we pass it in to our s to our chart chart handling so let's do that so we'll go back to our uh prices index or let's see charts index so right now our chart just has um a div with a container and then high charts i think we might actually ultimately make this show up on like a company show page where a specific company has specific prices but for now we're just sort of still messing around and getting it right so let's go into our high charts data instead of making this fetch call to the cdn i'm going to comment that out so we still have access to it and then i'm going to change this to slash api prices and that will give us back some price data price data that we want to ultimately like map into data which is going to be what is expected here so this is going to be this will be fun this will be fun so let's the way that i'm thinking about doing this is adding a break point right here on the terminal so we'll reload and then we can just experiment in the console so let's go to slash charts and let's go to here and refresh the page and it's saying 404 not found api slash prices but it totally wait we were just there api slash prices oh you know what we need to pass an id right yeah yeah so here um company id is equal to one so when i'm prototyping i usually don't worry too much about making it super generic so like you might be wondering like should we be putting this on a company show page right now and making sure that it's like dynamic and it renders the different charts for different companies uh and those are the types of things that i like to figure out later because i think those are sort of the easier steps right like okay we could just put this into some i don't know some tool that takes in the id for the company and then like knows how to render the prices for that um so instead i want to just get it working get the hard parts like the unknown unknowns working first and then i'll come back and figure out like exactly what this thing looks like um when it's when it's a real real situation okay so refresh the page and now we should have if we hit this step over we should have some price data in a minute so let's see step over and okay maybe come back here let's put a break point on that point and then say play okay so now we should be able to experiment with price data directly in the console so i think i want object dot entries for price data and that will give me back an array of arrays and so if we look at the first one that is a okay so it's a tuple here of the date as a string and the number as a string so we're going to be able to parse parse float the second value and so yeah let's see so we want to map this onto i think we can actually say like the date is the okay so map takes a function as an argument right so map is going to take in a function and i wonder if you can see this all right let me move this to sorry one sec let's get this thing in the bottom there we go okay so object.entries for price data is going to give us back a list of tuples where the first element is the date and the second element is the price um and so we're going to take that array of tuples and we're going to map over it and i believe we can de-structure so we can use array destructuring in the parameter list for the function we're passing in and say this is the date and this is the price and let's say for now we want to just get back the date and parse float of the price and see how far that gets us now if we look at one of these items okay so now the price has been properly converted from a string to a float so that's step one uh oh gosh uh we lost our code here okay so we have object entries.map and then we want to change the date from a string value into a unix timestamp so i think we want to say like date.parse maybe i can never remember these ones so let's just grab like the first element too oh my gosh was it that easy i don't know we'll see so we're gonna say const data is object dot entries price data dot map and we're gonna have some arguments and the arguments are going to be structured into an array of the date and the price and we want to return a new array where we have the date and the price but the price parse float we parse the price string value into a floating point value we say date.parse the date value into a unix timestamp and then let's just refresh the page and see what happens and okay so we see a warning here what is the warning what is this high charts warning number 15. all right what is that this happens when creating a line series or stock chart where the data is not sorted oh gosh in ascending order okay so um all right so zero or actually let's see uh so let's go back and add another break point uh here where do we go where do we go this is too big i can't actually see it uh okay so webpack webpack which one are we on application packs i don't know what that says hi chart okay here here's where we're at so let's refresh the page now if we have data zero da data zero zero data one zero okay now these are two these should be like two unix timestamps right and if we look at the first one 401 and if we look at the second one uh 331 okay so i think it might be just in the in the wrong or like the opposite order like i think the the first element in the array needs to be okay so this is why we kept this this is why we kept this uh this around this this url around so let's take a look and see so the first element in this array is 270101 and the second element in the array is 2070102 so we have it ordered backwards so i think we just reverse it let's see dot reverse i don't know if that's a thing let's see so i'm going to just clean this up just a little bit so we can see it all and refresh the page and what do we got we don't have any oh my word look at that look at that that is a real those are real prices holy moly okay now what's really cool is if we go out to like okay let's see okay so this is going to be like the year-to-date price right so for this is for um pagerduty so we go to finance.yahoo.com and we go to pagerduty uh and then we look at like what does the one year price look like all right so we've got some stuff we have a little peak and then we have a flatten out so we've got a little bit of stuff we have a peak and then we flatten out super cool so the scale the scale there we go if we like squish it in like this then it ends up looking a little bit closer so this is definitely this is definitely working and that's kind of like what our goal was for this this video was just to get the prices on to our chart so just as a quick recap we had to create a new controller we created a new api controller called prices which uh looks up the company by id and renders back just the price data that we got from alphavantage earlier and then mapped into just a date to close of the day price for a certain company and then we implemented a quick transform here in javascript where we got the entries for those for that dictionary and then we mapped those entries and parsed them from string values for dates into unix timestamps and then we also parsed the string values for the floating point price into a floating point value and then we had to reverse it because it expects that uh the data is in sort of ascending order um and then we just we haven't yet actually messed around at all with high charts to change to change the look and feel for high charts but at this point i'm pretty happy with what's what we've got here thanks so much for watching in the next episode we're going to show how to build a company show page where we'll embed these charts and then we will load the chart based on the company that we're looking at and then we're going to put some flags based on trades cool thanks for watching --- [Back to all videos](https://www.cjav.dev/videos) --- ## Hey Agent, thanks for visiting! 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