README.md

Module 5 - Angular Dependency Injection and Promises

Projects:

fun-with-di	Introduction to angular Dependency Injection
fun-with-promises	Introduction to Promises in Javascript

Introduction to Dependency Injection

• We talked about the motivation to use a dependency injection infrastructure
• We saw how to create a service - an object encapsulating a bit of logic and perhaps data
• We defined the terms:
  • Consumer - the object that requires dependency
  • Injection request - A consumer that asks for a dependency (service) in the constructor
  • Injector - An object responsible for resolving (providing, injecting) the injection request
  • Provider - The algorithm, or logic, used to resolve the injected object
• We saw how to define injecter and provider using the providers property of a Module, or Component
• We understood the effect of defining a component as injector, and how to use the component hierarchy as injector hierarchy
• We saw how to define a provider that used another class instead of the requested class
• We saw how to use the following explicit providers:
  • Class provider
  • Existing provider
  • Value provider
  • Factory provider
• Finally, we saw how to define a service as Injectable so it can also consume dependencies
  • We saw the "tree shakable" syntax that uses the @Injectable decorator to set the root provider

Introduction to Promises and Async Development

• We defined a promise as an object that tells us if an action that takes time has completed, and what is the result
• We saw that we can not "pull" that information, but rather have to use the .then and .catch methods and provide callbacks that will be called when the promise completes
• We saw how to create a promise using the Promise Constructor.
• We understood what async and await keywords do and how do they affect the compilation