When working with Angular 2, services can be "provided" in three different places:

1. During bootstrap
2. In the root component
3. In other components or directives

The "bootstrap provider" option is specifically designed for configuring and customizing Angular's pre-registered services, such as routing support. For more information, refer to this resource.

If you require only one instance of a service like NameService throughout your entire application (i.e., Singleton pattern), you can include it in the providers array of your root component:

@Component({
   providers: [NameService],
   ...
)}
export class AppComponent { ... }

Check out the Plunker example

Alternatively, if you prefer each component to have its own instance of the service, you can use the providers array within the component's configuration object:

@Component({
   providers: [NameService],
   ...
)}
export class SomeOtherComponentOrDirective { ... }

For more detailed information on this topic, refer to the Hierarchical Injectors documentation.

With the release of Angular 2 Beta:

To make your service injectable, incorporate @Injectable into your code like this:

@Injectable()
export class NameService {
    names: Array<string>;

    constructor() {
        this.names = ["Luna", "Ethan", "Sophia", "Mateo", "Olivia"];
    }

    getNames() {
        return this.names;
}

Then, in your component configuration, include the provider by adding providers as shown below:

@Component({
    selector: 'my-app',
    providers: [NameService]
})

To properly utilize the NameService, make sure to inject it into the providers array within your AppModule's NgModule metadata.

@NgModule({
   imports: [BrowserModule, ...],
   declarations: [...],
   bootstrap: [AppComponent],
   // Add providers below to share a single instance throughout the app
   providers: [MyService]
})
export class AppModule {

}

If you need to create a dependency for a specific component without affecting the overall state of your application, you can inject that dependency in the component's providers metadata section as demonstrated in the answer provided by @Klass.

Surprisingly, there have been more syntax changes in the latest Angular version :-) According to the Angular 6 documentation:

Starting with Angular 6.0, the recommended method for creating a singleton service is to specify that it should be provided in the application root. This can be achieved by setting providedIn to 'root' on the @Injectable decorator of the service:

src/app/user.service.0.ts

import { Injectable } from '@angular/core';

@Injectable({
  providedIn: 'root',
})
export class UserService {
}

To properly inject NameService, ensure that it is added to the providers array in your AppModule's NgModule metadata.

@NgModule({
   providers: [MyService]
})

Also, remember to import it in your component using the exact same name as specified in the providers array, as SystemJs is case sensitive. If you have different path names in your project files like this:

main.module.ts

import { MyService } from './MyService';

your-component.ts

import { MyService } from './Myservice';

System js will end up making double imports in this scenario.

When using Angular version 2 and above, the syntax has been updated to:

@Component({
    selector:'my-app',
    providers: [NameService],
    template: ...
})

Angular 2 has undergone some changes, so let's take a look at how the beginning of your code should now appear:

import {
  ComponentAnnotation as Component,
  ViewAnnotation as View, bootstrap
} from 'angular2/angular2';
import {NameService} from "./services/NameService";

@Component({
  selector: 'app',
  appInjector: [NameService]
})

It might also be beneficial to implement getters and setters in your service like this:

export class NameService {
    _names: Array<string>;
    constructor() {
        this._names = ["Alice", "Aarav", "Martín", "Shannon", "Ariana", "Kai"];
    }
    get names() {
        return this._names;
    }
}

Then within your application, you can easily access the names by doing:

this.names = nameService.names;

I recommend going to plnkr.co to create a new Angular 2 (ES6) plunk and test it out there first. Once everything is functioning correctly, transfer it to your main environment and address any issues that may arise.

Encountering the error message No provider for NameService is a challenge commonly faced by newcomers to Angular2.

Cause: In order to utilize any custom service, it must first be registered with NgModule by adding it to the providers list:

Resolution:

@NgModule({
    imports: [...],
    providers: [CustomServiceName]
})

One way to declare dependencies is by including them in the bootstrap command, like so:

bootstrap(MyAppComponent,[NameService]);

In my experience with alpha40, this method was successful for me.

For more information, you can visit:

Greetings! Below is the code snippet you can utilize in your .ts file:

Start by importing your service into the .ts file:

import { Your_Service_Name } from './path_To_Your_Service_Name';

Next, include providers: [Your_Service_Name] in the same file:

 @Component({
      selector: 'my-app',
      providers: [Your_Service_Name],
      template: `
        <h1>Hello World</h1> `   
    })

Include it in the providers section instead of injectables

@Component({
    selector:'app',
    providers: [NameService]
})

When it comes to registering a service in Angular, there are two main ways to do so:

1. Registering a service in the module or root component:

Effects:

• Accessible in all components
• Accessible throughout the application's lifetime

It is important to note that when you register a service in a lazy loaded module:

• The service will only be available within components declared in that module.

• The service will be available for the duration of the application's lifecycle only when the module is loaded.

2. Registering a service in any other component within the application:

Effects:

• A separate instance of the service will be injected into the component

Take caution when registering a service in any other component within the application:

• The injected service instance will only be accessible within the component and its child components.

• This instance will be available for the lifetime of the component.

To include your service in the providers[] array of the app.module.ts file, follow these steps:

// Here is an example where the service is named CarService

app.module.ts

import {CarService} from './car.service';

providers: [CarService] // Add as many services as you need

Make sure to include it in the providers array, which contains all dependencies for your component.

Refer to this section of the angular documentation:

Registering providers in a component

Take a look at this HeroesComponent example 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: `
  <h2>Heroes</h2>
  <hero-list></hero-list>
  `
})
export class HeroesComponent { }

When to use NgModule versus an application component

Providers in an NgModule are registered in the root injector, making them accessible throughout the entire application.

In contrast, providers registered in an application component are only available within that component and its children.

For example, the APP_CONFIG service needs to be accessible across the application, so it is registered in the AppModule @NgModule providers array. On the other hand, since the HeroService is specific to the Heroes feature area, it should be registered in the HeroesComponent.

Refer to the NgModule FAQ for more information on app-wide providers registration.

In your situation, simply replace injectables with providers like this:

@Component({
  selector: 'my-app',
  providers: [NameService]
})

Keep in mind that some features like @View have been removed in newer versions of Angular.

For additional details, visit here.

Blockquote

Adding Service Providers to a Component

Check out the updated HeroesComponent below, which includes registering 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 { }

When using Angular2, it is necessary to specify all injectables in the bootstrap function. Failure to do so will result in your service not being treated as an injectable object.

bootstrap(MyAppComponent,[DataService]);

To make your service Injectable, add the following line of code:

export class NameService {
    names: Array<string>;

    constructor() {
        this.names = ["Alice", "Aarav", "Martín", "Shannon", "Ariana", "Kai"];
    }

    getNames() {
        return this.names;
    }
}

In your component, include the providers as shown below:

@Component({
    selector: 'my-app',
    providers: [NameService]
})

If you wish to access your service throughout the entire application, you can use app provider instead.