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Getting Loopier
9:11Use v-for to loop through an array of objects and add Vue directives to provide interactivity to each and every item in the array.
Let's code our first simple Vue project.
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For the rest of this part of the course,
we'll be creating and
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accordion menu of different pieces of
media, books, videos and streaming videos.
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Imagine that this is the front end for
a public library.
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Libraries don't just deal in books
these days, but in all sorts of media,
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magazines, DVDs, streaming videos,
CDs, Ebooks and more.
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So we're going to build a way
to filter items by type and
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this filter will dynamically populate with
different media items based on our data.
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We'll also be able to click any piece of
media to display more information about
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that piece of media.
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And program the arrows to point up or
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down to indicate whether a specific
accordion item is open or closed.
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So here's what we're starting with.
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To follow along,
download the project files, and
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open up the folder called accordion.
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Let's take a look at app.js.
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We have here an array of
objects called media.
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Each object has a title,
description, type, contributor, and
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a property called showDetail,
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which is a Boolean, much like in the
bookDetail example we looked at earlier.
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Below our array of objects,
we have a Vue instance attached or
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mounted to an html element
with an id of media-list.
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Notice that we've set
the array of media objects
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to the property, mediaList.
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In the HTML, we have an unordered
list containing a single item.
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That item contains a heading tag and
two paragraph tags surrounded by a div.
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We're going to use a structure to
display an ad functionality to
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any number of media items.
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We also have a select menu that
currently contains one default option.
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Let's start by looping through each
object in our array of objects and
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displaying the data.
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We'll loop through our array of objects
in pretty much the same way we did
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in the last video.
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In this case, the data we want to
loop through is called media-list.
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So, I'll put a v-for
directive on the list item.
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And inside of the v-for directive,
I'll say media in mediaList.
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Remember, media here represents
each object in our array.
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Let's put media in curly braces inside
of the heading 3 tag to see what we get.
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If we take a look at this in the browser,
you can see that between the heading
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3 tags, we're actually
displaying the entire object.
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So we know that everything
is hooked up correctly, but
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this format isn't super useful quite yet
so let's fix that.
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First, let's take a look at our
Vue instance in our Vue Dev tools.
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I'll open up dev tolls by right
clicking anywhere on the page and
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selecting inspect.
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And then I'll choose Vue from the top menu
and then I'll click on the root instance.
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If we expand mediaList here,
we can see each object,
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along with its keys and values.
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In our Vue template,
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we can access any of these values as
we would any object with dot notation.
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Let's go back to our template and
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display just the title
inside of the heading 3 tag.
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To use that notation
inside of a Vue template,
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I'll need to use whichever alias I've used
here to refer to each individual object,
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followed by whatever
the property is called.
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So, if I want to access
the title property,
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Then I'll say, media.title.
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Let's save and
take a look at this in the browser.
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Great, we're displaying each individual
title instead of the whole object.
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Back in our template, let's add the
description and contributor to each item.
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I'll replace Media Description
with media.description.
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Now let's take a look at this again,
and awesome.
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Now you can see with just
a little bit of code,
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we're printing out some
nicely formatted content.
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Now let's quickly add the hide and
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show functionality like we
did in an earlier video.
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In fact, I encourage you to
pause the video for a moment and
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see if you can set it up for yourself.
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I'll leave the link to the video in
the teacher's notes if you want to review.
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That'll remind you how I did it and
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also show you an additional
way to get the job done.
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Note that last time we put
our click event on the h3.
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But in order to preserve this nice
formatting, and make our accordion menu
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that much more user friendly, we'll want
to program main accordion to open and
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close whenever the user clicks
anywhere on the list item.
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Don't worry if you got stuck, sometime you
have to see something a couple of times
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before it sticks, and
that's perfectly okay.
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In our Vue template,
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I'm going to add a v-show directive to the
div surrounding the two paragraph texts.
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In the quotes, I'll access
the showDetail property using .notation.
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Remember, for each object in the array,
Vue is going to look at the showDetail
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property and show or hide the detailed
information based on whether or
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not show detail evaluates to a true or
false value.
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To ensure that this is working
we can look in Vue Dev-tools.
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Access an individual object and
toggle show details on and off.
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But first, let's remember to refresh.
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There we go, now it's working great.
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The details are showing and
hiding in real time.
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Now, we just need the same
thing to happen on click.
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Back in our template,
let's add a click event to the list item.
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As we did in an earlier video,
we'll say v-on:click,
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and then whatever
the value of showDetail is,
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we will change it to the opposite value.
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See if this works, and it does, fantastic.
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However, this is getting a little long, so
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I'd like to move this logic
over to its own function.
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So I am going to go ahead and cut this.
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And we'll move it into
a method called toggleDetails.
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I'll go to app.js, And below data,
create a new methods object.
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Inside that we'll add a property called
toggleDetails, And paste our logic in.
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Let's check it out, and oops,
we have a problem here.
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The problem is that Vue actually
doesn't know anymore which
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list item we're referring to.
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How can we let Vue know which
list item we've clicked on so
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that it knows which item to open and
close.
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Well, because we're looping through a list
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we need a way to tell Vue which
object we're referring to.
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So we can pass media as
an argument into the click event.
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Let's save, go to app.js, and I'll add
a parameter called media to this method.
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And inside the function,
all console.log(media), just so
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it's extra clear what we're doing here.
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Now let's look at this in the browser.
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Open up the console.
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Looks like we forgot an s here.
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Great, now it's working and you can see
that each time we click on a list item
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it's logging the specific
object that we clicked on.
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So using a parameter
here gives us access to
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all the information we need to work
with the object, inside of the method.
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