112. Creating a Data Service

Jul 15, 2026 04:41 · 6:41 · English · Whisper Turbo · 2 സ്പീക്കറുകള്‍

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We saw how to use that logging service in the last lecture.

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Now let me show you another typical use case for a service to

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store and manage our data.

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So for example,

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our accounts.

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Right now I store them here in the app component and then we have this

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chain of property and event binding to get data to the app

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component so that we there can update our accounts.

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Let's create a service for that.

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The account service maybe.

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So I will create this and I will export

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my accounts.

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service class here,

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just like that.

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And here,

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I will now copy in my accounts.

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So I will remove them from my app component and paste them into

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my accounts service.

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And I will add a add account method here,

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where I simply expect to get account name and status.

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And I will add

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a update

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status method where I expect to get the ID of the account I want to update

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and then the new status here.

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Now the logic for these two methods is basically the same

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as in the app component.

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For a new account or in the add account,

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I simply want to push a new account onto my array of

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accounts.

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And here I will simply quickly create a new object where I assign the

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name and the status.

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So the data we get passed into this method.

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for the status changed well here I basically

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want to also just access my

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account with that ID here and set the status to,

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well,

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the new status we get passed as an argument too.

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So with that,

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this service looks all right.

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We got our accounts there and we got our methods to

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change something there.

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Of course,

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the app is broken though.

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Because for one,

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I don't need that code in the app component anymore.

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If we have a look at the app component template,

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we still loop through all the accounts here.

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So I should still have my accounts here in the app component,

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but we removed them from here.

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They're now in the service.

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So we should maybe re -add them here.

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But now this should simply be an array of accounts.

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So each account object has a name,

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which is a string and a status,

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which is a string.

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So I'm just defining the type here.

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And we want to have an array of such objects.

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Initially,

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it should be an empty array.

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This is what I'm saying here.

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Now, since we have our account service,

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we should inject it here as we learned it.

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So let's add our accounts service here of

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type account service.

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The type is super important to inform Angular about what we need here.

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Let's close this body of the constructor and

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make sure to add the import at the top pointing to your account service

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file.

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Now,

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what did we learn?

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We also need to add a provider.

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So here at the providers array,

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we should add accounts service so that Angular knows

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how to create such an account service.

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With that,

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we can now add,

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for example,

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onInit,

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this onInit lifecycle hook,

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as most initialization should not be done in the constructor,

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but instead here,

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and simply set this accounts

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accounts equal to this account service which is available

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as a property because I use this shortcut with the accessor in front of

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the argument name and here

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I can access my accounts field.

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Just as a little note,

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since accounts here is an array,

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it is a reference type.

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This is normal JavaScript behavior.

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So this is a reference type.

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So by setting it equal here,

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we're actually getting access to the exact same array as stored in

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the service, just as a side note.

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So with that,

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we do have access to the accounts.

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And if we save this and have a look at

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our application,

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This still seems to work.

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These buttons will not work and will actually give us errors because I removed the event

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listeners.

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But in general,

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this looks alright.

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We can see the free accounts which are now stored in our account service.

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So with that,

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let's go back to our application.

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And here I now want to update the account component and the

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new account component.

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Let's start with the new account.

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Here we no longer need to emit this event here

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because we're not listening to it anyways.

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So we can get rid of the output here,

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get rid of the imports up here of event emitter and output.

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And instead,

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we should inject our service,

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our accounts service of type accounts

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service.

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And what did we learn?

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We should provide it,

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right? So let's add account service,

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account service,

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and make sure to add the import at the top.

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Now with this in here,

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I can call account service add account and

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pass the account name and the account status as this is

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what this method expects to get as arguments.

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So with that,

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let's go to our account component now.

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Let's also get rid of the output here.

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We still need the inputs because we're still receiving that data from outside.

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And we can get rid of this event calling here.

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We remove the output anyways.

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Get rid of the imports we don't need anymore.

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And now here,

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I also want to get access to the account service.

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So let's inject it here too.

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Maybe in a new line to make it more readable.

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The accounts service of type

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accounts service like this.

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Make sure to add the import at the top.

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And let's add it to the providers array here.

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With that,

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I can now call it here,

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account service,

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call update status,

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pass my ID,

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and the new status again.

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This is what this method expects.

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If we now save this and go back to our application,

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it looks all right,

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but we quickly realized that if we click on add account,

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We don't get an error,

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we get the log,

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but I don't see the account.

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If I click these buttons,

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I also see the log,

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but I don't see the change here.

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So something is not working correctly.

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It seems like it doesn't,

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right? Well,

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let's have a look at what's going wrong here in the next lecture.

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