Angular 4: When and why is @Inject is used in constructor?

Question

Problem Statment

I am learning Angular 4 and I have stumble upon a code where @Inject is being used in a constructor and I am

Answer 1

If MAT_DIALOG_DATA is a non-factory/class dependency (like string for your configs), you usually use @Inject.

Also check InjectionToken: https://angular.io/guide/dependency-injection#injectiontoken

One solution to choosing a provider token for non-class dependencies is to define and use an InjectionToken

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Here's a plunker: http://plnkr.co/edit/GAsVdGfeRpASiBEy66Pu?p=preview

if you remove @Inject in these cases you will receive a

Can't resolve all parameters for ComponentName: (?)