How to keep only one instance of service for several components?

Question

I use DI to inject sevice in several components. Now it works not as one common instance.

I trie to load service in app.module in section providers

Then you should have a singleton. Provide a complete minimal example reproducing the problem. — JB Nizet, Jul 23 '17 at 13:29

score 6 · Accepted Answer · answered Jul 23 '17 at 13:29

If you add a provider only to @NgModule({providers: [MyService]}) (and nowhere else) then there will only be exactly one instance of MyService in your application.

This is only true when the @NgModule() decorator is on a non-lazy loaded module. Providers of lazy-loaded modules can be imported with forRoot to ensure they will be singletons as well.

If you add a service to @Component({ providers: [...]}), then there will be as many instances as there are instances of this component.

How to keep only one instance of service for several components?

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