Join Justin Schwartzenberger for an in-depth discussion in this video The Opaque Token, part of Angular 2 Essential Training.
- So the inject decorator with its string literal works,…but there is a better way to do this.…Relying on string literals for tokens…is always a bit of a risk.…They are harder to maintain, easier to mistype,…and code editors don't have much opportunity…to keep track of them to aid in refactoring.…Angular has a solution for this.…It's called an opaqueToken.…You can use an opaqueToken to tell Angular…you want to have a concrete type that can be passed around.…
So let's refactor the lookup list value type…to use an opaque token.…First, let's create a new file called providers.ts…in the app folder,…and let's move the lookup list value instantiation…from the app.module.ts file,…and put it into this new file.…Now the provider metadata property in the app module…is going to need this lookup list variable,…so let's add the export keyword…in front of the const statement,…so that we can import it in the app.module.ts file.…
To create an opaqueToken, we need to import the class type.…It's part of the angular core scoped package,…
Justin Schwartzenberger steps through the framework one feature at a time, focusing on the new component-based architecture of Angular 2. You'll learn what Angular is and what it can do, as Justin builds a full-featured web app from start to finish. After mastering the essentials, you can tackle the other project-based courses in our library and create your own Angular app.
- What is Angular?
- Setting up an Angular template
- Creating a component
- Binding events and properties
- Getting data to components
- Using directives and pipes
- Creating Angular forms
- Validating form data
- Understanding dependency injection
- Providing services
- Making HTTP calls
Skill Level Intermediate
1. Architecture Overview
3. Directives and Pipes
5. Dependency Injection and Services
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