Angular: Understanding Modules and Services

Reference

• Feature Modules:
  • Must declare all the components, directives, and pipes it needs.
  • Every module which is not the AppModule is technically a Feature Module, and it has to declare all the components, directives, and pipes that it needs.
  • It is not enough to declare a component once in the declarations array of AppModule - in order to use a component in a module, it MUST be declared in that specific module.
  • BrowserModule must be imported in AppModule (it’s required in order to run the app in the browser), this module must not be imported elsewhere: we must import CommonModule.
  • Feature Modules define all of the views, as each view will have its own module. Also, each “view module” can be lazy loaded by the route via loadChildren.
  • preloadingStrategy - Check out preloadingStrategy: PreloadAllModules.
• CoreModule
  • Global services should be AppModule.
  • Every laze module has its own injector. A service provided in a lazy module is only accessible in that module. But it can still access the services provided by non-lazy modules.
• Shared modules
  • exports makes components, directives, pipes, and even other modules available to the importing modules!