APP_INITIALIZER is run when the application starts to initialized. The multi : true create the multi provider, Make sure you enter the(*)required information where indicate.HTML code is not allowed. Observables added unnecessary complexity to ConfigurationService which will make our implementation harder to understand and test. How can I wait for all my promises to be achieved in the right order How can I make sure that my config AND my user is set before everything else ? After loading the configs you can resolve the promise. This is good because each factory will have injected its own dependencies only. It will call the initialize method. With this definition we can reuse the existing factories as they already createaFunctionthatreturnsaPromise. It means we could have multiple APP_INITIALIZER providers, not just this single provider. When adding a new disk to Raid1 why does it sync unused space? It means were injecting ConfigurationService as dependency. Lets find a way to remove coupling. Where developers & technologists share private knowledge with coworkers, Reach developers & technologists worldwide.
Now in your unit test for configurationService you dont have to create a spy or any other trick for the dependent functions, just pass an empty array for the configDeps. But is this recommended? I tried this in my application module but the application starts right after the config is loaded, and doesn't wait for my user service. Is possible to extract the runtime version from WASM file? Each one needs to be provided using a factory that will return the function executed by Angular. However, in order to load configuration from endpoint B and C, I had to get first the base URL from endpoint A. Angular has a hook in its process of initialization called App Initializer. Follow-up: Number of points on an elliptic curve, How to encourage melee combat when ranged is a stronger option. APP_INITIALIZER is an injection token that allows you to provide one or more initialization functions. Help us improve this content by Endpoint A contains some core configuration such as base URL. ConfigurationService will have a ready$ Observable property that will emit a stream when configuration data has been set after request A is resolved. And thats how we deal with config in Angular. Lets keep factories decoupled but lets get rid of complexity of Observables in this early phase of the application, keeping ConfigurationService untouchedandthingssimple. we cann't do it directly from the provider. I will not delete the post because it might help other people who wants to know how to wait for several promises to be done before loading the application. In this article, were going to learn how to use Angular APP_INITIALIZER injection token. Making statements based on opinion; back them up with references or personal experience. Connect and share knowledge within a single location that is structured and easy to search. This token allows you to provide multiple App Initializers. rev2022.7.21.42635. Cool! if any of the initializers returns a promise then the angular waits for it to resolve, before continuing with the app initialization. Can a timeseries with a clear trend be considered stationary? Is "Occupation Japan" idiomatic? Example: and add them as parameter to our initialize method. So it's solved. loading environment config and then calling a userService. When you want to load the application configuration when the application starts, youll need to use APP_INITIALZER. This ensures that the configuration will always be read when your application is loaded. It uses the simplicity of nesting dependent requests of solution one and creating multiple factories from solution two, but in this case Im going to provide only one App Initializer and a custom Injection Token that will handle factories B and C. ConfigDeps is the new Injection Token of type (() => Promise
To subscribe to this RSS feed, copy and paste this URL into your RSS reader. What's inside the SPIKE Essential small angular motor? You can use this method to load configurations and initialize your app. We ended up with a solution that is maintainable and easy to test at the same time. Our app.component.ts will log App Component initialized as following: Thats It, weve successfully implemented APP_INITIALIZER token. All we have to do next is to use the factories for creating the functions, put them into an array and return the array. When it comes to dependency issues, why dont we use Angulars Dependency Injection system?, isnt that what it was made for? Could a license that allows later versions impose obligations or remove protections for licensors in the future? Learn on the go with our new app. Although we have our requests decoupled, which is a good thing, there are still some issues. (instead of occupation of Japan, occupied Japan or Occupation-era Japan). A friendly maintainability testing relationship. Also check weve created factory function. Movie about robotic child seeking to wake his mother, How to help player quickly make a decision when they have no way of knowing which option is best, Laymen's description of "modals" to clients. This basically means that the factory used for this provider should return an Array of Functions where each Function should return a Promise. But for the simplicity, well call github api to get the user information here. Angular suspend the app initialization until all the funciton provided by the APP_INITALIZER are run. But before going to that lets check out the wrong place to store the configs. This is only because is easier to test.