Skip to main content
Ben Nadel at cf.Objective() 2014 (Bloomington, MN) with: Mehul Saiya
Ben Nadel at cf.Objective() 2014 (Bloomington, MN) with: Mehul Saiya ( @mehulsaiya )

Exploring Dependency-Injection Tokens Using Pictures In Angular 2

Published in Comments (4)

The other week, I carried out a fun little exploration in using class delegates or class proxies in the dependency-injection mechanism in Angular 2. While I don't think this will be a terribly common use-case, the exploration really forces you to think about how dependency-injection tokens work and how they are mapped to provider instances by the hierarchical injector. This can lead to a non-trivial mental model. So, as suggested by Sean (in the comments of said post), I wanted to try and articulate this crazy mind map a little bit more clearly.... using pictures:


Exploring provider tokens in the Angular 2 dependency-injection mechanism.  

As you can see, the "common case" is actually pretty straightforward - you use a Class as the provider token for the single instance of that class. But, once you step outside the common use-case, it can start to get quite a bit more hairy. And this graphic doesn't even attempt to look at all the different use-cases for the various provider types (ie, class vs. value vs. factory, etc.). But, hopefully this graphic does sheds a little light on how tokens map to instances in the Angular 2 dependency-injector; and, how you can use that mechanism to do some interesting things.

Reader Comments

I believe in love. I believe in compassion. I believe in human rights. I believe that we can afford to give more of these gifts to the world around us because it costs us nothing to be decent and kind and understanding. And, I want you to know that when you land on this site, you are accepted for who you are, no matter how you identify, what truths you live, or whatever kind of goofy shit makes you feel alive! Rock on with your bad self!
Ben Nadel