Angular no provider for NameService

Question

I ve got a problem loading a class into an Angular component  I ve been trying to solve it for a long time  I ve even tried joining it all in a single file  What I have is   Application ts       lt reference path     typings angular2 angular2 d ts    gt   import  Component View bootstrap NgFor  from  angular2 angular2   import  NameService  from    services NameService     Component       selector  my-app       injectables   NameService      View       template   lt h1 gt Hi   name   lt  h1 gt           lt p gt Friends lt  p gt           lt ul gt              lt li  ng-for   name of names  gt   name   lt  li gt           lt  ul gt        directives  NgFor      class MyAppComponent       name string      names Array lt string gt        constructor nameService NameService                this name    Michal           this names   nameService getNames            bootstrap MyAppComponent     services NameService ts  export class NameService       names  Array lt string gt       constructor             this names     Alice    Aarav    Mart  n    Shannon    Ariana    Kai              getNames                 return this names            I keep getting an error message saying No provider for NameService   Can someone help me spot the issue with my code

User · Answer

Angular2 requires you to declare all the injectables in bootstrap function call  Without this your service is not an injectable object   bootstrap MyAppComponent  NameService

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In Angular v2 and up it is now    Component       selector  my-app       providers   NameService       template

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You need to add it to providers array  which includes all depency on your component   Look at this section in angular documentation      Registering providers in a component      Here s a revised HeroesComponent that registers the HeroService in its   providers array    import   Component   from   angular core    import   HeroService   from    hero service     Component     selector   my-heroes     providers   HeroService     template       lt h2 gt Heroes lt  h2 gt     lt hero-list gt  lt  hero-list gt         export class HeroesComponent          When to use NgModule versus an application component      On the one hand  a provider in an NgModule is registered in the root   injector  That means that every provider registered within an NgModule   will be accessible in the entire application       On the other hand  a provider registered in an application component   is available only on that component and all its children       Here  the APP CONFIG service needs to be available all across the   application  so it s registered in the AppModule  NgModule providers   array  But since the HeroService is only used within the Heroes   feature area and nowhere else  it makes sense to register it in the   HeroesComponent       Also see  Should I add app-wide providers to the root AppModule or the   root AppComponent   in the NgModule FAQ    So in your case  simply change injectables to providers like below    Component     selector   my-app     providers   NameService       Also in the new versions of Angular   View and some other stuffs gone   For more info  visit here

User · Answer

add your service to providers   array in app module ts file  Like below      here my service is CarService  app module ts  import  CarsService  from    cars service    providers   CarsService     you can include as many services you have

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Add  Injectable to your service as   export class NameService       names  Array lt string gt        constructor             this names     Alice    Aarav    Mart  n    Shannon    Ariana    Kai               getNames             return this names            and in your component add the providers as    Component       selector   my-app       providers   NameService       or if you want to access your service all over the application you can pass in app provider

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You have to use providers instead of injectables     Component       selector   my-app       providers   NameService       Complete code sample here

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You should be injecting NameService inside providers array of your AppModule s NgModule metadata    NgModule      providers   MyService       and be sure import in your component by same name  case sensitive  becouse SystemJs is case sensitive  by design   If you use different path name in your project files like this   main module ts  import   MyService   from    MyService     your-component ts  import   MyService   from    Myservice     then System js will make double imports

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Shockingly  the syntax has changed yet again in the latest version of Angular  -   From the Angular 6 docs      Beginning with Angular 6 0  the preferred way to create a singleton   services is to specify on the service that it should be provided in   the application root  This is done by setting providedIn to root on   the service s  Injectable decorator    src app user service 0 ts  import   Injectable   from   angular core     Injectable     providedIn   root      export class UserService

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Blockquote   Registering providers in a component  Here s a revised HeroesComponent that registers the HeroService in its providers array   import   Component   from   angular core    import   HeroService   from    hero service     Component     selector   my-heroes     providers   HeroService     template           export class HeroesComponent

User · Answer

Angular 2 has changed  here is what the top of your code should look like   import     ComponentAnnotation as Component    ViewAnnotation as View  bootstrap   from  angular2 angular2   import  NameService  from    services NameService     Component     selector   app     appInjector   NameService       Also  you may want to use getters and setters in your service   export class NameService        names  Array lt string gt       constructor             this  names     Alice    Aarav    Mart  n    Shannon    Ariana    Kai              get names             return this  names            Then in your app you can simply do   this names   nameService names    I suggest you go to plnkr co and create a new Angular 2  ES6  plunk and get it to work in there first  It will set everything up for you  Once it s working there  copy it over to your other environment and triage any issues with that environment

User · Answer

Hi   You can use this in your  ts file    first import your service in this  ts file    import   Your Service Name   from    path To Your Service Name     Then in the same file you can add providers   Your Service Name       Component         selector   my-app         providers   Your Service Name         template             lt h1 gt Hello World lt  h1 gt

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The error No provider for NameService is a common issue that many Angular2 beginners face    Reason  Before using any custom service you first have to register it with NgModule by adding it to the providers list   Solution    NgModule       imports             providers   CustomServiceName

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You should be injecting NameService inside providers array of your AppModule s NgModule metadata    NgModule      imports   BrowserModule           declarations            bootstrap   AppComponent        inject providers below if you want single instance to be share amongst app    providers   MyService     export class AppModule        If you want to create an Dependency for particular component level without bothering about state of your application  then you can inject that dependency on component providers metadata option like accepted  Klass answer shown

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As of Angular 2 Beta   Add  Injectable to your service as    Injectable   export class NameService       names  Array lt string gt        constructor             this names     Alice    Aarav    Mart  n    Shannon    Ariana    Kai               getNames             return this names            and to your component config add the providers as    Component       selector   my-app       providers   NameService

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Add it to providers not injectables    Component       selector  my-app       providers   NameService

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In Angular you are able to register a service in two ways   1  Register a service in module or root component  Effects    Available into all components Available on lifetime application   You should take care if you register a service into a lazy loaded module    The service is available only into components declared into that module The service will be available on lifetime application only when the module is loaded   2  Register a service into any other application component  Effects    Will be injected a separate instance of the Service into the component   You should take care if you register a service into any other application component   The instance of the injected service will be available only into the component and all of its children  The instance will be available on the component lifetime

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In Angular 2 there are three places you can  provide  services    bootstrap root component other components or directives    The bootstrap provider option is intended for configuring and overriding Angular s own preregistered services  such as its routing support   -- reference  If you only want one instance of NameService across your entire app  i e   Singleton   then include it in the providers array of your root component    Component      providers   NameService             export class AppComponent           Plunker  If you would rather have one instance per component  use the providers array in the component s configuration object instead    Component      providers   NameService             export class SomeOtherComponentOrDirective           See the Hierarchical Injectors doc for more info

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You could also have the dependencies declared in the bootstrap-command like   bootstrap MyAppComponent  NameService      At least that s what worked for me in alpha40   this is the link  http   www syntaxsuccess com viewarticle dependency-injection-in-angular-2 0

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