WEBVTT

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Hi everyone!

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We already know what is the.

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A tightly coupled and loosely coupled, right?

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And the idea of inversion control is in the inverse the control.

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Okay.

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We are already familiar with that right.

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And in this video let me refactor the existing cost.

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Into the.

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Inversion of control.

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So how I can do that.

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If you notice in the app.controller.ts, it use the syntax like this, right?

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It is something similar, but right now I will forcus on that

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I will comment this this thing.

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Okay, this is clear a tightly coupled

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And in order to reverse that, we will use the constructor okay.

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And with the constructor we will have a test service.

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Very similar with the the video.

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The previous video.

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And I will use this.

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And we must initialize the test service.

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Test service.

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And testService = testService

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That is.

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And actually we can use access modifier in right here, I will use the private and this will be work.

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But in app controller is used very shorthand syntax.

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Right.

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And actually we can use that, instead of initially right here and right here, we can use something like

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this.

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Let let me show you.

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I will comment, I will duplicate and comment.

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Right here.

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I can remove here remove here and provide a private.

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Okay.

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That's it

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This a similar with here.

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Okay.

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But this is a shorthand method.

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We can use the private into directly inside the constructor parameter.

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And this will work.

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And we can use the read only to make sure we don't change.

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We we don't change the test service.

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Okay.

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Read only.

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And if I remove everything right here Now, can you guess it worked or not?

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Well, if I go to the calc here because the calc get method right here is use the test service

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Right.

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If I go to here and if I refresh.

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Now it's not working.

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Right.

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The.

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It's crashed my application.

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Right.

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And in order to understand this issue, we will discuss on the dependency injection.

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Okay.

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Dependency injection.

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And because we already know what is the tightly coupled and loosely coupled

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And we already understand the inversion of control.

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Now let's understand the dependency injection.

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I will see you in the next video.