113. Understanding the Hierarchical Injector

Jul 15, 2026 04:41 · 2:41 · English · Whisper Turbo · 1 സ്പീക്കറുകള്‍
ഈ തീയതിയുടെ കാലാവധി ഇന്നു് തീരുന്നു. സ്ഥിരമായുള്ള സ്റ്റോറേജ് അപ്ഗ്രേഡ് ചെയ്യുക →
ലാപ്‌സ് ഇന്‍ഡെക്സ്
കാണിക്കല്‍ മാത്രം.
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
In the last lecture we set up our account service and hooked it up in our app
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
and still our app seems to be broken.
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
If I click these buttons the status is not changed.
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
So somehow our code is not working.
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
Actually it's working correctly.
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
We're just using services wrong here.
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
In this specific case we're not using the service in the way we should
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
use it in our app.
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
What's going wrong?
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
the Angular dependency injector actually is
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
a hierarchical injector.
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
That means that if we provide a service in
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
some place of our app,
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
let's say on one component,
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
the Angular framework knows how to create
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
an instance of that service for this component and,
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
important, all its child components.
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
And actually,
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
this component
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
and all its child components and the child components of the child components
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
will receive the same instance of this service.
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
There are other places where we can provide a service too.
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
The highest possible level is the app module.
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
We haven't done this yet,
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
but we will see this soon.
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
If we provide a service there,
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
The app module does have a provider's array.
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
The same instance,
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
and that's important,
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
the same instance of the class of the service is
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
available in our whole app,
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
in all components,
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
in all directives,
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
in all other services where we maybe inject a service.
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
Yes, we can inject services into services.
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
I'll come back to this.
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
The next level,
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
for example,
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
would be the app component.
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
There,
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
the app component and all its child components do have
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
the same instance of the service.
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
And this is true for any component.
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
So even if we have a child of the app component,
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
if we provide it on that child,
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
all the children of this child will have the same instance and the child
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
itself, but not the app component.
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
The instances don't propagate up.
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
They only go down that tree of components.
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
The lowest level,
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
therefore, is a single component with no child components.
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
If we provide a service there,
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
this component will have its own instance of the service,
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
and,
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
well, it doesn't have any child components,
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
so this instance will only be available for this component.
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
And this will actually even overwrite if we were to provide
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
the same service on a higher level.
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
And that's exactly what we're doing.
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S… Speaker 1 (113. Understanding the Hierarchical Injector)
So let's take a closer look in the next lecture.

ഈ അക്ഷം AI (സ്വയമുണ്ടായി അക്ഷരാനുഗ്രഹം) ഉണ്ടാക്കിയത്. പിശകുകള്‍ ഉള്‍ക്കൊള്ളാം. അല്ലെങ്കില്‍ മൂല ഓഡിയോ ഉപയോഗിക്കുന്നതിനു് മുന്‍കൂട്ടിയുള്ള പിശകുകള്‍ സ്ഥിതീകരിക്കാം. ഐഐ നയം

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