Dependency Injection is like a virus, once you start to use it, it spreads
until it is the only way to make objects...
The Books service is now a method parameter to the Book. You need to pass
it in. If you can't new a Books instance (which you shouldn't) then you
should inject it into the BooksCreateComponent:
class BooksCreateComponent {
constructor (books : Books) {}
create(){
let book = new Book(this.books);
boook.id = 149;
book.name = 'TMA - 1';
book.create();
}
}
That is the easiest/shortest route, but my suggestion would be to avoid
newing the Book if you can. I realize you have params to send to the Books
create() method, but do you need to use an instance of Book to store/send
those parameters to Books? How about:
class BooksCreateComponent {
constructor (books : Books) {}
create(){
let bookConfig = {
name: "TMA - 1" as string,
id: 149 as number,
...
};
let book = this.books.createBook(bookConfig);
}
}
You use an Object Literal to create the data to pass to the books service,
it is just a data transport object, not really part of your model. Then
you rely on your service to create the model, so it can sync with storage
and the server, or whatever is needed. And you never new the model,
because that could lead to desync and a 2 step creation process.
On Friday, July 8, 2016 at 11:36:57 PM UTC-4, Supun Budhajeewa wrote:
>
> I've a question about injecting a service into a domain model, in a way
> that it'd allow me to instantiate (`new`) that domain model.
>
> Imagine I have a domain model called `Book`. I need to inject a service
> called `Books` into this domain model, so that I can call the
> `Books.create()` method from the `Book.create()` method.
>
> If I inject the service dependency in the domain model's constructor, I am
> not able to `new` that domain model, unless I pass an instance of the
> service into the domain model.
>
> Domain model:
>
> ~~~
> class Book {
> id: number;
> name: string;
>
> constructor (
> private Books: Books
> ){}
>
> create (){
> this.Books.create(//pass data here);
> }
> }
> ~~~
>
> Component:
>
> ~~~
> class BooksCreateComponent {
> create(){
> let book = new Book(); //This fails unless I pass in an instance
> of Books service.
>
> boook.id = 149;
> book.name = 'TMA - 1';
>
> book.create();
> }
> }
> ~~~
>
> Any idea how I should proceed?
>
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