Description#

Any injected provider must be visible within the module scope (loosely speaking, the containing module) of the class it is being injected into. This can be done by:

• defining the provider in the same module scope
• exporting the provider from one module scope and importing that module into the module scope of the class being injected into
• exporting the provider from a module that is marked as global using the @Global() decorator

Injection tokens#

Can be types (class names), strings or symbols. This depends on how the provider with which it is associated was defined. Providers defined with the @Injectable() decorator use the class name. Custom Providers may use strings or symbols as the injection token.