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Hi everyone.

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Let me summarize the dependency injection techniques a little bit.

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Actually, the dependency injection is a design pattern.

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Okay.

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Now.

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When we mark the class will be injectable, and import it's inside the provider of the module.

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What's actually happened under the hood, it will create the something called IOC container.

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Inversion of control container or dependency injection container.

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This will be the same.

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Okay.

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But I think I will go.

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That will be the IOC container.

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And when we mark the object will be @Injectable.

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And import it inside the module providers.

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It will create the IOC container and pass the object into here.

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Test service

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Okay.

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And test repo

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Okay.

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And later, when the some controller wants to access into the test service, it will auto look up inside

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the IOC container and take the test service.

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Okay.

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And pass it inside the parameter of the constructor.

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You can see, it will pass it directly right here.

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Into the controller.

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And all of that are done by the.

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NestJS framework.

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Okay.

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Hopefully this makes sense right.

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Let me write a flow one more time.

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Firstly

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--

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Firstly, the controller.

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The controller is say: it has a dependency.

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Okay.

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The controller.

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The controller I have a dependency.

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And for that reason, it will look up into a IOC container.

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And.

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Say.

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In this case will be test service object creation.

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Okay.

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Test service object, not test service class.

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Okay.

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This is clearly the object creation.

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Okay.

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It will take test service object and pass it inside the controller.

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Okay.

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That's the how.

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Dependency injection work.

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Hope you understand this video.

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I will see you in the next one.