115. Injecting Services into Services

Jul 15, 2026 04:42 · 5:13 · English · Whisper Turbo · 1 Сөйләүчеләр

Бүгенге көндә бу бинада китапханә эшли. Кайвакытлы саклау өчен яңарту →

Укыту индексы

0:02

S… Speaker 1 (115. Injecting Services into Services)

In the last lecture,

0:03

S… Speaker 1 (115. Injecting Services into Services)

we learned about this hierarchical injector and that we can choose

0:08

S… Speaker 1 (115. Injecting Services into Services)

between one instance or multiple instances of the same service class.

0:12

S… Speaker 1 (115. Injecting Services into Services)

I mentioned that the highest possible level is

0:16

S… Speaker 1 (115. Injecting Services into Services)

actually not the app component.

0:18

S… Speaker 1 (115. Injecting Services into Services)

So let's remove it here,

0:19

S… Speaker 1 (115. Injecting Services into Services)

this providers array,

0:21

S… Speaker 1 (115. Injecting Services into Services)

leave it in the constructor and leave the import.

0:23

S… Speaker 1 (115. Injecting Services into Services)

But the highest possible level is in the app module.

0:27

S… Speaker 1 (115. Injecting Services into Services)

Here,

0:28

S… Speaker 1 (115. Injecting Services into Services)

we also have a providers array added if you don't have it.

0:32

S… Speaker 1 (115. Injecting Services into Services)

And here we can also provide the accounts service.

0:36

S… Speaker 1 (115. Injecting Services into Services)

Make sure to also add the import at the top here then.

0:39

S… Speaker 1 (115. Injecting Services into Services)

With that little addition here,

0:43

S… Speaker 1 (115. Injecting Services into Services)

we're making sure that our whole application,

0:46

S… Speaker 1 (115. Injecting Services into Services)

everything in our application,

0:47

S… Speaker 1 (115. Injecting Services into Services)

receives the same instance of the service unless it overrides it

0:52

S… Speaker 1 (115. Injecting Services into Services)

as we did before.

0:53

S… Speaker 1 (115. Injecting Services into Services)

Now with that,

0:54

S… Speaker 1 (115. Injecting Services into Services)

we can now even inject a service into another service

0:59

S… Speaker 1 (115. Injecting Services into Services)

because that's not possible by providing it on a component level.

1:02

S… Speaker 1 (115. Injecting Services into Services)

For that,

1:03

S… Speaker 1 (115. Injecting Services into Services)

we need to provide it in the app module.

1:05

S… Speaker 1 (115. Injecting Services into Services)

So let's say we want to log something if

1:09

S… Speaker 1 (115. Injecting Services into Services)

we call an action in the account service.

1:12

S… Speaker 1 (115. Injecting Services into Services)

So I would have to provide the logging service in

1:16

S… Speaker 1 (115. Injecting Services into Services)

my app module now.

1:18

S… Speaker 1 (115. Injecting Services into Services)

And therefore,

1:19

S… Speaker 1 (115. Injecting Services into Services)

I will simply comment out providers here in my add

1:23

S… Speaker 1 (115. Injecting Services into Services)

component decorators.

1:25

S… Speaker 1 (115. Injecting Services into Services)

And I don't want to call logging

1:29

S… Speaker 1 (115. Injecting Services into Services)

service here anymore.

1:30

S… Speaker 1 (115. Injecting Services into Services)

So we'll comment this out.

1:32

S… Speaker 1 (115. Injecting Services into Services)

And I will actually leave the injection here so that you have it for reference if

1:36

S… Speaker 1 (115. Injecting Services into Services)

you download the code.

1:37

S… Speaker 1 (115. Injecting Services into Services)

I'll also comment it out here in new account component.

1:40

S… Speaker 1 (115. Injecting Services into Services)

Instead,

1:41

S… Speaker 1 (115. Injecting Services into Services)

let's say I want to use this logging service in the account service.

1:45

S… Speaker 1 (115. Injecting Services into Services)

And I might want to call the log status change method there.

1:49

S… Speaker 1 (115. Injecting Services into Services)

Because this is in the end the place where the status changes.

1:51

S… Speaker 1 (115. Injecting Services into Services)

Either because we added a new account or because we called update status.

1:55

S… Speaker 1 (115. Injecting Services into Services)

So to use the service there.

1:59

S… Speaker 1 (115. Injecting Services into Services)

Generally, we start in the same way.

2:01

S… Speaker 1 (115. Injecting Services into Services)

We add a constructor and we inject our logging service in

2:05

S… Speaker 1 (115. Injecting Services into Services)

this case.

2:06

S… Speaker 1 (115. Injecting Services into Services)

Set the type.

2:07

S… Speaker 1 (115. Injecting Services into Services)

Import this type at the top.

2:10

S… Speaker 1 (115. Injecting Services into Services)

Make sure to add the import.

2:12

S… Speaker 1 (115. Injecting Services into Services)

And we provided it an app module.

2:15

S… Speaker 1 (115. Injecting Services into Services)

So you could think that we are set to go.

2:17

S… Speaker 1 (115. Injecting Services into Services)

That we can now go to add account,

2:19

S… Speaker 1 (115. Injecting Services into Services)

call logging service,

2:21

S… Speaker 1 (115. Injecting Services into Services)

log the status change,

2:23

S… Speaker 1 (115. Injecting Services into Services)

pass the status here.

2:25

S… Speaker 1 (115. Injecting Services into Services)

and do the same here for update status.

2:28

S… Speaker 1 (115. Injecting Services into Services)

You could think this is how we do it,

2:29

S… Speaker 1 (115. Injecting Services into Services)

and it's not unlogical to think so,

2:32

S… Speaker 1 (115. Injecting Services into Services)

but let's see if this works.

2:33

S… Speaker 1 (115. Injecting Services into Services)

If we load our app,

2:36

S… Speaker 1 (115. Injecting Services into Services)

we already get an error.

2:38

S… Speaker 1 (115. Injecting Services into Services)

Can't resolve all parameters for account service.

2:42

S… Speaker 1 (115. Injecting Services into Services)

Something's not working.

2:44

S… Speaker 1 (115. Injecting Services into Services)

The reason is if you inject a service into something,

2:48

S… Speaker 1 (115. Injecting Services into Services)

this something needs to have some metadata attached

2:53

S… Speaker 1 (115. Injecting Services into Services)

to it.

2:53

S… Speaker 1 (115. Injecting Services into Services)

Now a component has some metadata because we have add component.

2:57

S… Speaker 1 (115. Injecting Services into Services)

A directive has some metadata because we have add directive.

3:01

S… Speaker 1 (115. Injecting Services into Services)

A service doesn't have

3:05

S… Speaker 1 (115. Injecting Services into Services)

any metadata.

3:07

S… Speaker 1 (115. Injecting Services into Services)

It's just how Angular works that we need to attach some metadata,

3:10

S… Speaker 1 (115. Injecting Services into Services)

and of course not any metadata.

3:12

S… Speaker 1 (115. Injecting Services into Services)

You shouldn't attach addComponent here.

3:14

S… Speaker 1 (115. Injecting Services into Services)

There is a specific metadata you should attach in such cases.

3:18

S… Speaker 1 (115. Injecting Services into Services)

It's addInjectable,

3:20

S… Speaker 1 (115. Injecting Services into Services)

which needs to be imported from addAngularCore.

3:24

S… Speaker 1 (115. Injecting Services into Services)

This tells Angular that now this service is

3:28

S… Speaker 1 (115. Injecting Services into Services)

injectable or that something can be injected in there to be precise.

3:32

S… Speaker 1 (115. Injecting Services into Services)

So that's important.

3:34

S… Speaker 1 (115. Injecting Services into Services)

You don't add add injectable to the service you want to

3:38

S… Speaker 1 (115. Injecting Services into Services)

inject, but to the service where you want to inject something.

3:42

S… Speaker 1 (115. Injecting Services into Services)

So the receiving service,

3:44

S… Speaker 1 (115. Injecting Services into Services)

you could say, that to be injected in service.

3:47

S… Speaker 1 (115. Injecting Services into Services)

And you don't need to add it to any other service.

3:50

S… Speaker 1 (115. Injecting Services into Services)

If you don't want to inject anything in a service,

3:52

S… Speaker 1 (115. Injecting Services into Services)

Like here for the logging service.

3:54

S… Speaker 1 (115. Injecting Services into Services)

You don't need to add add injectable.

3:56

S… Speaker 1 (115. Injecting Services into Services)

Only add it if you expect to get something injected.

4:01

S… Speaker 1 (115. Injecting Services into Services)

Now, one important note here,

4:02

S… Speaker 1 (115. Injecting Services into Services)

as I explained,

4:04

S… Speaker 1 (115. Injecting Services into Services)

we don't need to add injectable,

4:06

S… Speaker 1 (115. Injecting Services into Services)

the injectable decorator here to this class,

4:08

S… Speaker 1 (115. Injecting Services into Services)

because this is a service which we only inject somewhere else,

4:12

S… Speaker 1 (115. Injecting Services into Services)

but where we don't inject anything into this service.

4:15

S… Speaker 1 (115. Injecting Services into Services)

And you technically really only need injectable if you inject something into this

4:20

S… Speaker 1 (115. Injecting Services into Services)

service, not if you just inject this service somewhere else.

4:23

S… Speaker 1 (115. Injecting Services into Services)

In newer versions of Angular,

4:26

S… Speaker 1 (115. Injecting Services into Services)

however, it is recommended that you always add

4:29

S… Speaker 1 (115. Injecting Services into Services)

at injectable it technically makes no difference right now in the future

4:33

S… Speaker 1 (115. Injecting Services into Services)

it might though so it's already a habit you might get into that you add

4:38

S… Speaker 1 (115. Injecting Services into Services)

it here i do omit it but you could consider adding it also to ensure

4:42

S… Speaker 1 (115. Injecting Services into Services)

that in the future it doesn't unexpectedly break what i explained about

4:46

S… Speaker 1 (115. Injecting Services into Services)

why you need it and that you don't need it here technically still holds though with

4:51

S… Speaker 1 (115. Injecting Services into Services)

this if i now save this and we let the app reload

4:54

S… Speaker 1 (115. Injecting Services into Services)

Now it works.

4:55

S… Speaker 1 (115. Injecting Services into Services)

And now you see that if I save this,

4:58

S… Speaker 1 (115. Injecting Services into Services)

we still log it to the console with the correct status.

5:01

S… Speaker 1 (115. Injecting Services into Services)

The same happens if I click here.

5:03

S… Speaker 1 (115. Injecting Services into Services)

But now everything is centralized into our service.

5:07

S… Speaker 1 (115. Injecting Services into Services)

And now we're also injecting a service into a service.

Бу транскрипция уйлап табылган (автомат сөйләм таныу) ярдәмендә ясалган. Анда хаталар булырга мөмкин - мөһим куллану өчен оригинал аудио белән тикшерегез. AI сәясәт

❤️ STT.aiне яратасызмы?

Тиздән

Бу терминның берничә мәгънәсе бар: Транссибирь тимер юлының Транссибирь бүлекчәсе

Бу транскрипция турында АА-дан сорагыз

Бу ысулның төп өстенлеге — ул җөмләнең эчтәлеген һәм аның эчтәлеген аңлатучы җөмләләрне аерып күрсәтә.

Башкасын күчерү