Name: Records in Elm
Uploaded: 2016-06-12T07:40:53-05:00
Description: Records are important data structures in Elm. In this lesson we learn to create a record as well as describe the record by creating a type. We will also see how these new types can be used to clean up our annotations.

Records are important data structures in Elm. In this lesson we learn to create a record as well as describe the record by creating a type. We will also see how these new types can be used to clean up our annotations.

https://app.egghead.io/api/v1/lessons/elm-records-in-elm/subtitles

Records in Elm

[00:00] Records are data structures in Elm. Let's create a record named Resources. This will contain resources that we want to store for learning Elm. The record structure is wrapped in curly braces. We will create a key value pair named Name, and set it equal to a string.

[00:21] A record can also hold different types. We can add isComplete as a bool and an ID as an int.

[00:30] Let's do a little set up to make this app run. We already importing HTML, but let's bring in everything with the double dots. In Main, let's reference a view function we are going to write, and pass in resources. Finally, create a view, and it expects resources and writes out name.

[00:51] We can access values from a record by using it's name and a dot and then then value. We will use forward function to pass it into text.

[01:04] Using square brackets, we can make a list of our records. While we're at it, let's add a link key value.

[01:20] Now that we have a list of items, we will need to map over them to transform our list into HTML.

[01:37] If we wanted, we could break up the view function by creating a function that handles the mapping of the list of resources.

[01:52] Right now, if we wanted to add a type annotation to resource list, it would look like this.

[02:12] Yikes. This is the shape of our data, but it's not very readable. We can break that out and create a resource type.

[02:21] This looks very similar to our actual record, but now we use semicolons. Use the keyword type, then alias, then the name of our new type.

[02:43] Alias says anytime someone refers to the capital R Resource, this is the structure of the data. Now we can use the name Resource in our type annotation.

[02:53] This says we are expecting a list of Resource. We could also create a type for that.

[03:07] Let's update our annotation again and add one for view. Let's verify that works.

[03:20] Being able to give a name to the structure of our data really cleans up our type annotations, and we now have the basics of records.

Records in Elm

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