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Angular-Directive-Project

Directives range from very basic to extremely complex. This project will build up to some somewhat difficult directives. Keep in mind that the format we're learning for directives is the same format used to build some extremely complex things in angular. Using directives often and well is one way to show you're a talented developer.

Starting Out

We've included only a few things for you to begin with. index.html, app.js, styles.css. At this point the best way to get more comfortable with angular is to initialize an app without relying heavily on boilerplate code (reusable code that starts out your projects for you).

You'll notice that in the index.html we've included the angular-route CDN. Yes, we'll be using angular's router here. Put an ng-view into your index.html.

  • In your app.js set up a config and set up our first route for when a user is at the '/home' url. If you're having trouble remembering how to set up the router go look at how you set up the router on the previous project. One way these projects will be beneficial to you is allowing you to look back at something you did and seeing how you got that something to work.
  • You may also want add an otherwise that defaults to /home.
  • Create a controller and a template file for this route in your app folder. Don't forget to include the controller as a script in your index.html
  • Check that everything is hooked up correctly. Try adding a div with some text in your home template just to make sure it's showing up. Once you've got that going you're ready to start on some directives.

Now let's make our directive. We'll start with a simple one that we can use to display information passed to it.

Step 1. Start your directive

Woot. When you're initializing your directive just remember that it works very similarly to how you start up a controller or a service. It can also be very helpful to think of your directive as a route.

  • Create your directive. You'll use the directive method on your angular module. It takes two arguments, the name string and the callback function, which will return the object that represents your directive.
  • When naming your directive give it a name with two words; dirDisplay would be nice, but anything works. Just remember it's best practice to give a directive a camel case name so that it's clear in your html what it is.
  • Also we're going to need a template html for our directive. We could do it inline, but let's make another file instead. Just name it something that makes sense for the name of your directive and put it in the same directory as your directive file.
  • For your template just make a <div> and inside a <h1> tag that says User.
  • Now in your home route html add in your directive. It will look like this if you named it dirDisplay: <dir-display></dir-display>
  • Start up your app and go to the home route. Check and make sure you see User where your directive was placed.
  • If you're not seeing it at this point it could mean a few things. Here's some more common issues.
  • You didn't link your directive in your index as a script.
  • Your name for your directive doesn't match the name in your html. Remember camel case becomes snake case so myDirective becomes <my-directive></my-directive>.
  • You're file path to your html template is wrong. You have to think of file paths in angular as relative to the index.

Here's some code to see just for this part, and just for the directive's js file.

var app = angular.module('directivePractice');
app.directive('dirDisplay', function(){
  return {
    templateUrl: 'app/directives/dirDisplay.html'
  };
});

What we're returning is the directive object. You won't see anymore code in this tutorial so it's important you get things working right and refer back to what you've already done to advance from now on.

Step 2. Advancing directives

Your directive should be loaded up now, but it's not really doing much. Let's make it better.

  • In your home controller. Make a variable on your $scope called user. Set it's value to
{
  name: "Geoff McMammy",
  age: 43,
  email: "[email protected]"
}
  • Now inside your directive's html specifically inside the <h3> tags display our new user's name.
  • Then inside maybe some <h4> tags display his email and age. This is going to work exactly the same as if it was just inside your home controller.
  • Reload the page and make sure it works.

This is still very cosmetic and really not all that useful. It needs functionality.

  • Add into your directive's object the link property.
  • The link property's value is a function definition that takes (generally) three parameters. scope, element, and attributes.

Unlike in other places with angular injection these parameter names don't carry meaning. The first parameter will always represent your $scope for that directive, the second will always be the element that wraps your whole directive, and the third will always be an object containing all the properties and values of the attributes on your directive in the dom. Try the following to get a feel for all three.

  • Add two attributes to your directive in your html. Like this - <dir-display test="myTest" my-check="checkItOut"></dir-display>
  • Now in the link property you've added console.log the three parameters in the function.

You'll see an object for scope that should look identical to the $scope of your html function. For element you'll see an object the represents the DOM wrapper for your directive. For attributes you'll see an object that will look like this:

{
  test: "myTest",
  myCheck: "checkItOut"
}

An important thing to notice is how it has again converted snake case to camel case for you. my-check became myCheck. Don't forget this. You'll run into this issue one day. It counts for both attributes and directive names.

To feel some of what the link function could do let's try this.

  • Add a ng-show to both the email and age wrappers. This should be familiar to you.
  • Now inside your link function add a click event listener to your element property. It's going to look just like jQuery.
element.on('click', function(){
  
})
  • Inside the click listener's callback add a toggle for the ng-show property you passed in. Along with a console.log to make sure things are connecting when you click.
  • Try it out. Don't call for a mentor when it doesn't work. Let's talk about that first.

You should see the console.log firing, but why isn't it toggling. This is going to be a common problem when working with the link function and event listeners. What we have here is an angular digest problem. The value is changing on the scope object, but the change isn't being reflected by our DOM. That's because angular isn't aware of the change yet. Anytime we cause an event to happen using something like jQuery or even angular's jQLite we need to let angular know that we've made a change.

  • Add this line of code in place of your console.log, scope.$apply().
  • Now try it out. It should be working now, so if you're still having issues it's time to debug.

What we've done is forced angular to run it's digest cycle. This is where angular checks the scope object for changes and then applies those to the DOM. This is another good lesson to learn for later. You'll most likely hit this when making changes to your element using event listeners.

Step 3. Directive's re-usability.

Now our directive has some extremely basic functionality. One of a directive's greatest advantages though is its ability to be placed anywhere and still be functional. Let's say instead we had a list of users instead of just one.

  • Change the $scope property in your home controller to be users and give it this array as its value:
[
 {
   name: "Geoff McMammy",
   age: 43,
   email: "[email protected]",
   city: "Provo"
 },
 {
   name: "Frederick Deeder",
   age: 26,
   email: "[email protected]",
   city: "Austin"
 },
 {
   name: "Spencer Rentz",
   age: 35,
   email: "[email protected]",
   city: "Sacramento"
 },
 {
   name: "Geddup Ngo",
   age: 43,
   email: "[email protected]",
   city: "Orlando"
 },
 {
   name: "Donst Opbie Leevin",
   age: 67,
   email: "[email protected]",
   city: "Phoenix"
 }
]
  • Now in your home HTML add a ng-repeat to the directive call. Tell it to repeat for each user in users.
  • Reload your page.

It's working! But why? How does each directive instance know what information to display?

  • In the link function console.log the scope parameter. Make sure it's outside of your click listener.
  • You'll see five print outs in your console. Open up any one of them and look to the bottom. Open up the user property.

It's exactly what we would want! But again why would that be the case? Don't get too caught up in this next bit if it's too hard to understand, but the ng-repeat is essentially making new tiny scope objects for each individual user in our users array. Now each of our directives is still getting a user property on the scope object just like the directive wanted in the beginning. Woot.

Step 4. Ramp it up with Isolate Scope.

Directives can do so much more. So let's make that happen. That means we should make.... a new directive!!! This directive's purpose will be to display a selected User and the weather in his/her/its location. Link it up just like the last one.

  • Create a js file for our directive and name it dirWeather. Make an html file named dirWeather.html. Link it up in your index.html and add the template to your new directive object.
  • In your directive's template give it an <h3> tag that says Weather just so we can know it's working.
  • Above your ng-repeat on dirDisplay add your new dirWeather directive.
  • If it's not working check the instructions above as to some common reasons why before asking a mentor for help.
  • If you're seeing the Weather text on your page then we're ready to try out the dreaded Isolate Scope.

The isolate scope object is one of the stranger API's in angular. I'm sorry but it is. Just refer to this for now.

scope: {
 string: '@',
 link: '=',
 func: '&'
}

The properties on the scope object represent the attributes on the directive in the html. Our example scope object here would look something like this in the html. <example-directive string="a string" link="user" func="updateUser()"></example-directive> The hard part here is the @, =, and &. They each have very important and distinct meanings.

  • @ says take in my attribute value as a string.
  • = says take in my attribute value as a two-way bound variable from the parent scope.
  • & says take in my attribute value as a reference to a function on the parent scope.

It's also critical to point out that once you add a scope object you have no isolated your directive's scope. Meaning, aside from the values passed in through attributes, this directive has no connection to the $scope of its parent.

That being said let's isolate our directive's scope. 😟

  • Add the scope property to your dirWeather.
  • Give it the value of an object with a property of currentUser whose value is '='. Remember in your html this will look like current-user. This is the third time I've said so don't expect it again.

This means that whatever comes into the currentUser attribute is going to be a value of the parent's scope object.

  • For now test this out by passing in users[0]. Find a way to show that users information inside your dirWeather's html. Remember inside your directive now the user is represented by currentUser.

Step 5. &? &!?

The '=' value on your scope object has created a two-way binding between users[0] and currentUser. Now let's try out the '&'.

  • On your home controller add a function called getWeather. It takes one parameter called city.
  • This function will make a call to a service so we'll need to create that.
  • Make a weather service. Name it something cool and creative like weatherService.
  • Inside the weather service make a function called getWeather that also takes one parameter, city.
  • Make an $http get to this url - 'http://api.openweathermap.org/data/2.5/weather?q='
  • After the q= add on the city parameter.
    • If you want you can test this out in postman. See what kind of data you get back. If it's the weather of that city then... you win!
  • Use $q to return a promise that only resolves with the data you want. Temperature (preferably not in Kelvin) and the weather description. Use console.log on the data coming from the $http request to get to what you want. You'll need to add both on an object that you resolve your new promise with.
  • On your home controller have it return the result of invoking the get getWeather function on the service. You should be returning a promise.
  • Now in your home route's HTML pass in the getWeather function to the dirWeather directive through an attribute called weather-call.
  • Add the attribute to your isolate scope object.

That was a lot of linking, but let's walk through it. Your controller has a function linked to the service, which is in turn linked to your directive. So if you run the weatherCall function in your directive it will go through your controller to your service and then back.

Now things get a little bit tricky. Angular's way of passing along arguments through a directive to your controller are tricky, but once you understand how to do it, it's not hard. I'm going to give an example here of how it works.

<my-directive pass-func="callFunc(data)"></my-directive>

Here's how it would look in your HTML. But where's the data supposed to be coming from? It seems that you'd rather be able to pass in data from your directive. Well you still can, you just have to essentially tell angular what do use as an argument to replace data when it calls that function in your controller. The actualy function call inside the directive will look like this.

$scope.passFunc({data: wantedData})

So what you'll do is pass in an object where the property name is what the argument is named in the HTML where you call the directive. That might sound confusing, but just look at the two code blocks above for a pattern. Note that pass-func becomes $scope.passFunc and data is being replaced with wantedData with the {data: wantedData} object. In our directive we want to replace city in the attribute call, for something else inside the directive. You'll follow the same pattern as above.

For now let's get things set up for that function call.

  • Add to the dirWeather directive object a property called controller.
  • It's value will be a function.

Yes, this is a controller specifically for your one directive. It works the same as any other controller, except you don't give it a name. It's $scope object will only be accessible within an instance of your directive. Don't forget to inject $scope in the function.

  • Inside your controller function run the weatherCall function with the city property from the currentUser on your $scope.
  • Here's where you need to make sure you've passed in a city argument in the attribute function call, and then replace that with your currentUser's city using an object with a city property.
  • The function call should return a promise, so call .then afterward and add the data onto your $scope to display both the weather and temperature of the currentUser's city. The properties can be named whatever makes sense to you.
  • You may also want to find a way to get rid of all the decimal places on your temperature.

Now you should have everything hooked up so it shows Geoff's data and the weather data for Provo. But is that good enough?

##Step 6. Ramping up our ramp up. Now let's change this so it shows the weather data for whichever user we select. We're going to need to use '&' again.

  • Make a function on the home controller that takes in a parameter and sets a property on the $scope to be that parameter. Maybe you see where this is going.

We want to get this function into our dirDisplay controller. But in order to do that we need to isolate dirDisplay's scope. This also means we need to pass in each individual user through the scope object as well.

  • To make it easier on ourselves, let's pass the current user from our ng-repeat into our directive through a user attribute. This way we can leave our two-way bindings as they are.
  • Also pass our new function that sets our current user from our home controller into our directive through a setUser attribute.
  • You'll need to add an argument in there again. Go with user.

Your scope object in dirDisplay should have two properties. setUser with the value of '&' and user with the value of '='. As before we're going to need to do some tricky stuff to get our argument back to our controller.

  • Call the setUser function inside our click event listener and pass in an object the sets our user argument to be the user on our directive's scope object. If you've forgotten this part go back up and take a look at how you did it before or the example in this README.

Whatever user you click on now should show up in the dirWeather directive as the current user. But we're missing one thing, we want to be able to see the weather for that user too. We'll have to do one more thing that will seem a little bit tricky at first, but it's good to learn if you don't know it already since it's actually used quite frequently.

We need to step up a change listener on our currentUser in the dirWeather directive. We'll use angular's $watch functionality. $watch is a method on your $scope that will watch for changes in a variable you give it. It works in two ways.

$scope.$watch('property', function(value){
  console.log("When $scope.property changes its new value is: ", value)
});

And

$scope.$watch(function(){
  return myVar
}, function(value){
  console.log("When myVar changes its new value is: ", value);
});
  • Remove the immediate function call that we have in there now. Maybe just comment it out for now because we'll use it in a bit.
  • Now call the $watch method on your scope and have it watch currentUser. Either way of using $watch is fine.
  • Have its callback run the $scope.weatherCall function just like you had it before.

One thing to note is that $scope.$watch will always run once to begin with. Since that's what we want here it's great, but just be aware of that.

If you've reached this point congratulate yourself. You've messed with some serious stuff today, namely directives. There are still a lot of things about directives that we can't possibly cover in a single project. If you like what we've done so far then you're in a good place to keep going. A developer who understands directives well can build a really clean looking code base. Just look at your home.html. It could have just two lines in it. If you're feeling good move on now to Step 7.

##Step 7. Finishing touches Try to work out these problems on your own.

  1. There should be a way to let the user know that the weather data is loading. Something that appears while our $http request is retrieving our data.
  2. The $http request shouldn't fire on both opening and closing a user's information.
  3. A color change for the currently active user would be nicer than showing that user's info inside the dirWeather modal. Or at least less redundant.
  4. Whatever else you want. We still haven't explored transclusion and ng-transclude so give that a try if you're feeling adventurous. Just know that it's a way for deciding where to put the HTML child elements of a directive. It's cool stuff that can involve some criss-crossing of scopes.