Also, all rendering APIs - ViewContainerRef.createComponent for example. Thatwont workwhen theProductServiceis actually making requests of a remote server. So in this tutorial, we will simulate getting data from the server with the RxJS of()function. @jimbarrett33 , I'm having the same issue . thanks! I see. If the framework is forced to block before it can even instantiate the component, there's no opportunity to customize the behavior - the user just stares at a blank screen or (worse) a half rendered component. @kamilmysliwiec Can you help implementing this async-provider-loader for Angular?

I am trying to provide ConfigService using APP_INITIALIZER and use ConfigService to provide InjectionToken via useFactory, which has dependency on ConfigService. We're a place where coders share, stay up-to-date and grow their careers. Another is to expose a promise on the ConfigService and let the API services use a .then() in the constructor. Edit: I figured out that when I hide the property behind a function call getPrime() { return; } it works. For those who want to load config from a server dynamically, they seem to be encouraged to use a kludge comprised of creating a ConfigService and then using APP_INITIALIZER to delay the bootstrapping just long enough to make an async call and inject the results into the ConfigService.

As shown below. While we could callgetProducts()in the constructor, thats not the best practice. Open theProductServicefile and import theObservableandofsymbols from RxJS. There are many solutions. Hi guys! :(. LOC is an important metric to measure developer productivity. We are storing all of our data, particularly configuration on our store and the way to access it is through selectors which returns observable. I'll try it out, thank you! Each view's controller then uses a factory to fetch said data from Session Storage. Currently developing futuristic smart-device, IoT connected, highway construction site safety system in EU. I've used constants for this where the file that defines the constant is dynamically generated to include the data (in my particular case, it's a file). This feature would be so useful for implementing reusable services in a more natural way only by injecting object-value tokens. Change other methods with Asynchronous Signature, Awesome Charts in Angular 13 with ng2-charts, Client-Side PDF Generation In Angular 13 With PDFMake, Dynamically Add Title and Meta Tags on Route Change in Angular, Integrate Google Analytics with Angular | Angular SEO. For those that don't mind slowing down the bootstrapping process a tiny bit extra, you can do the async requests before bootstrapping. Press question mark to learn the rest of the keyboard shortcuts,, Still no other solution other than using fetch. If your app needs some initial settings but they are asynchronous calls, whats the best way load that data before your app starts? Another way to work around this, at least until angular actually support async providers is to inject a value object, which then gets updated using Object.assign(valueObj, serverResponse). The key point here is that I want to avoid having to expose async APIs all around due to a singleasync operation required onlyat bootstrap.
The workaround is to have some setup(config) function in the service that is called from an app_initializer to make use of async factory but I prefer the first option, it's more cleaner.


Writing something like this: is very tempting, unfortunately, at the time Im writing this article, asynchronous constructors are not supported in Typescript. @Cassidie How has this approach been working out for you? @maplion I haven't ran into any issues with the approach. The obvious solution would be to introduce async provider initialization. Observable.subscribe()is the critical difference.

So, for example, just use dynamic config for what's needed to show the user the first first view and put the rest on a timer or something. There are several fundamental ideas and conceptual links in them. Pretty standard use case. This asynchronous approachwill workwhen theProductServicerequests products from the server. I've never had a use case where these two methods didn't work, however in the chance you are in this situation, you should look into $q to manually perform promise resolution. Specifically to my case, we are using a 3rd party library with services that expect to receive configuration data as Injection Tokens.

If we make rendering asynchronous, not only is it bad for performance, but it limits how the application can surface that it's currently in a loading state. The need hasn't diminished in 3 years; why would we give up now @cerireyhan ? I hope this helps someone! This can be done fairly cleanly: @alxhub Thank you for your arguments and logical justifications. Async is for when you want stuff to happen while other stuff is waiting to happen, so if that is not the scenario here, then don't use async. something that no longer is supported by PWA applications, so I need another solution. Angular's DI system is designed to be synchronous, and we have no plans to make this kind of fundamental change, for a few reasons: Rendering in Angular today is synchronous. I would LOVE to see this feature! This url comes from a fetch to the server. We will change these methods in the HTTP chapter.

    This is called software blocking and at least lets the user begin using the site/data/bundles that have arrived. Now refresh the browser and check the output, you will get the same output as we have seen in the previous chapter, but this time we are doing asynchronous calling of getProducts() and getProduct(). We extraced the relevant code into an own service and made replaced the specific promises inside our services with a more or less declarative configuration. Sign in

    @mischkl hmmm, I don't think so APP_INITIALIZER tokens as multi providers and their dependencies are initialized first. I just want to be able to dynamically load an appConfig asynchronously and I can't quite get things to work. For a one time download (resolved from the home view I'm assuming) that's needed across multiple views, I have taken to dropping the now resolved and delivered data file (presumably .json) into Session Storage. @muuvmuuv , we have been using this approach for the same purpose you mentioned: If you are not using websockets, just ditch the splitlink part and use: For the sake of completion, this is how we import the module: Wow @rafagsiqueira, I want to kiss you rn. Is it going to be developed after ivy is ready? , [1], Just ran into this issue today. {{ post.title }} How to deal with inferred TypeScript types and stop using any, Implement Hybrid Decorator Functions in TypeScript. Here We will not convert addProduct() and deleteProduct() methodof PorductService into asynchronous signature. NestJS (which is a node.js backend framework yet similar to Angular) supports asynchronous providers[1], and it is a highly praised feature.

    Fair warning for when you attempt to upgrade. IE: If you're expecting 7 bundles of data before you want the view displayed, init the var to 7 and decrement it each time an async call is received. Just wanted to voice my +1 for this as well. Any suggestions would be appreciated. I've tried many different amalgamations and permutations to try to resolve the races consistently, but nothing works consistently as fetching before the application loads in the main.ts -- something that no longer is supported by PWA applications, so I need another solution. I can only imagine that with time they will appear many more use cases because observables are everywhere so, to me, it makes perfect sense to make angular provide built-in support for these scenarios. The service will first call someOtherService.doSomething() which returns a promise. It can take a callback. appId: 'fbkeyid-dynamicvalue' .

    The closest I've come is: But APP_CONFIG is not populated early enough and services loaded from my CoreModule or components that need DI injection of the token need it before it is ready and no matter what I try, I can't seem to get an architecture that makes them wait long enough.

  • If you need to perform an action on the data when it comes in I use. Hi @projectX21 I think well need more information to assist you, are you using the APP_INITIALIZER to get the LOCALE data and set in your project? Till now, we have created the getProducts(), getProduct(), addProduct() and deleteProduct() product in ProductService. I gave up Angular because Web Assembly Blazor is way better! I have a bunch of server side C# enumerations (lookup data) that I don't want to recreate or hard code in JS. A solution to this would also promote real re-usable Angular libraries. Currently, it is rare to find a project that hasn't adopted Reactive Programming or even better, Redux using ngrx. to your account. When that is resolved it will do the $http.get() to get the users.

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    The only thing I see is something like this: Have a look at this plugin: Angular has grown a lot since its first release and the entire community has grown as well, patterns has been creating and a lot of idea has been adopted from other successful frameworks as well. You could have a global called IS_INIT that counts how many outstanding calls remain open. There are workarounds, of course. What I'd like is to have a phase in which I initialize serviceB, loading its state and having it fully functional again, and only then allow serviceA to be able to use its API (after having loaded, Once all the state is loaded and the services are "initialized", only then should controllers access them - at which point I'd like the API to be used in a. Now the views will update when the data comes in. The above method likely forfeits some browser resource loading / work parallelism by making everything wait for the config so early in the bootstrap processing, before other work might get started. TheProductServicemust wait for the server to respond,getProducts()cannot return immediately with product data, and the browser will not block while the service waits. DEV Community 2016 - 2022. Why is this still not a thing? I feel like I have to pick which hack I want to implement to get this to work. I'm not presently using Angular, but am using its injection functionality via inject-js. @gmaughan You're the man; your solution works exactly like I need. Reserve the constructor for simple initialization such as wiring constructor parameters to properties. In case you want to forbid clients to use the constructor, and force them to go through your factory method, you can also declare the constructor as private., Feature (core module): add application config at runtime,,,,, if you put the code to just one ConfigService, it would work, or because APP_INITIALIZER is a multi provider you can have more services and just their declaration order in, it's likely that much of the stuff you're trying to configure can be baked Angular environment files so it's not needed to configure dynamically. Angular doesn't seem to support providers which asynchronously create their object / service.

    Dveloppeur web et passionn de finances personnelles. As the plunkr demonstrates there may be other ways to reproduce the problem, but at least when using Effects I haven't found a way to solve the problem via structural changes. Sign up for a free GitHub account to open an issue and contact its maintainers and the community. Made with love and Ruby on Rails. TheProductsComponentconsumes thegetProducts()result as if products could be fetched synchronously. It uses XMLHttpRequest rather than fetch to build the configuration before bootstrapping the Angular module. We have an Angular 6 Library that is just domain services that I want others in the org to use. It's still hacky, but should at least allow other client services to use a more simple object. I think reading config in a constructor is pretty common programming practice. Before we update the getProducts() method in ProductsComponent, lets move the service call code from constructor to the ngOnInit(). I think it would be great to be able to do something like: (notice the useAsyncFactory idea to tell ng that it should wait on the promise, and use the value it produces as the service) Let's say the initialization calculates some random prime number which takes about 200ms to finish. Thank you!!! yeah, this is what i ended up doing, it seems like this is the easiest every time i think of this situation. This is the relevant part in my forRoot() providers[]. The previous version assigns an array of products to the componentsproductsproperty. As a result, when I load my application I'd like to be able to "initialize" my services with their previous state (taken from the indexDB), which is an async opertaion. All the rest is waiting.

    Having asynchronous services would make component rendering asynchronous, because any individual component could not be created without perhaps waiting for a dependency to resolve. I went with what I thought was the cleanest approach. Well occasionally send you account related emails. Its there, but you cant assign it.

    One way is to use an asynchronous init method, which will need to be called by the client. @maplion I've been using a solution I mentioned above in PWA applications successfully for a while now. Ideally I'd like to be able to return an observable from my factory provider to register that I can subsequently inject. +1 I wanted to add my to support this feature request. Once suspended, slavius will not be able to comment or publish posts until their suspension is removed. The good news that we've got more hooks now into providers definition, most notably on the route level. Instead of loading the data via JavaScript, have the server fetch the data and embed it in the rendered HTML. It was so simple man I really need to learn thinking simpler sometimes. it's been 3 years, maybe we should give up? Used to work on infrastructure, application architecture and cloud engineering. & How to learn it in a day? The constructor shouldntdo anything. By the way console.log inside useFactory is executed first and then comes the console.log from inside the APP_INITIALIZER. One thing you can do is have an initialized promise on each service: You do not have permission to delete messages in this group, Either email addresses are anonymous for this group or you need the view member email addresses permission to view the original message. I believe though that does not cover my requirement to get that value as observable to be able to wait for it to finish and continue my code inside the component when the value is ready. In theHTTP tutorial, we will callHttpClient.get()which also returns anObservablethat emitsa single value, an array of products from the body of the HTTP response, Now you will get the error in the ProductsComponent as.

    See the related discussion in #17606 (comment). // now we can subscribe to it, whenever input changes, // listen to data as long as groupPosts is undefined or null,, Updated on September 15, 2020, DigitalOcean Kubernetes: new control plane is faster and free, enable HA for 99.95% uptime SLA, // each post will have a title and category,

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    I cannot believe this has been an issue for so long! This is extremely frustating.

    They might become supported by the language in a future version, but meanwhile, how can we deal with async operations in the constructor of a class ? The Locale, which is returned in the response, should be set for the LOCALE_ID, so that the pipes (date, currency) are localized.

    In my project the user's language will be determined in a REST-call.

    Because now the ProductService.getProducts() method returns Observable. Thanks in advance! awesome, i didn't know this cache property existed. Although promise chaining indeed solves the problem is requires my service's API to be async, which, in my case it really shouldn't be. Whenever you inject this service it simply calls the factory function ONCE and caches the return so all subsequent injections will use the same object: The resolve functionality of $routeProvider does not really know about services or have any concept of service initialization. // Ensure Angular destroys itself on hot reloads. Now subscribe this method in ProductDetailComponent as shown below. By clicking Sign up for GitHub, you agree to our terms of service and However the constructor does not call any of it. Thensubscribe passes the emitted array to the callback, which sets the componentsproducts property. It's unfortunate that this hasn't been fixed, but at least we've got some ideas that work! This is exactly what I use. It certainly shouldnt call a function that makes HTTP requests to a remote server as arealdata service would. Built on Forem the open source software that powers DEV and other inclusive communities. A lot of init's do not need to be async. After too many hours im frustratingly giving up. We will resolve this error by subscribing the getProducts() methodin ProductsComponent.

    For further actions, you may consider blocking this person and/or reporting abuse. Highly request from our company as well, we are using Apollo with persistent caching, which uses async local storage functionality to hydrate the cache, without this we are not able to load the cache before services make requests to our API. #20383. Just beware, this doesn't actually solve the problem of ensuring the configs are ready. With you every step of your journey. This has to be a pretty common thing and it shouldn't be this hard. I'm curious what kind of feedback I'd get. Instead, callgetProducts()inside thengOnInit lifecycle hookand let Angular callngOnInitat an appropriate timeafterconstructing aProductsComponentinstance. Have a question about this project?

    Hi @BruneXX: thank you for your imediate answer. ProductService.getProducts()must have anasynchronous signatureof some kind.

    I can post a sample if anyone's interested. I've seen quite a few other users trying to accomplish the same thing on Stackoverflow. For example: There is no concept of initialization. how to subscribe the asynchronous method in Component. ;). You can find more details at, [AngularJS] Re: async service initialization,!topic/angular/6CxwIL4QSfY/discussion, Once it hits 0 you are ready to go. A community for the awesome MVC JS framework. Once unpublished, all posts by slavius will become hidden and only accessible to themselves. I want to have finished ConfigService with ready to use config file and then provide InjectionToken via using this ConfigService.

I have the same problem. The problem is that inside the useFactory I get the ConfigService but it is not resolved yet. :(. Instead, asynchronous dependencies should be modeled within the values injected, not within the DI system itself.

Because we are returning the last promise in the chain, our resolve will not conclude until every single promise in the chain has resolved, so this should handle any sort of dependency structure. Check this repo maybe could bring you an optimal solution Agree, probably the best way to go. './app/core/interfaces/app-config.interface', './app/core/services/env.service.provider', // This gets the environment from a javascript file. @mischkl but isn't it just a different organizational point of view because: The problem is that some services are defined in other modules and imported into the app module, in which case they are initialized first. Of course if there would be some async function to call (e.g. and only accessible to Slavius. Before I go with the workaround of fetching data during bootstap I want to check with you.

For example: If in order for the user service to return the users it depends on some other service method which is also async, there is nothing stopping it from waiting on the other services promise before resolving its own. Use a resolve in your initial route config.

Currently, configured like MyModule.forRoot( environment.whateverConfig ) in app.module.ts. It will become hidden in your post, but will still be visible via the comment's permalink.

I've got it to work in the meantime. Did you find a temporary solution to the problem. DEV Community A constructive and inclusive social network for software developers. an HttpClient) I would return a Promise or Observable and subscribe to it in the Component. The main complaint for me is simply that APP_INITIALIZER is only a partial solution since it only holds up component initialization but doesn't know anything about the service side of things. In the next chapter of HTTP Services, we will learn that Angular HttpClient methodswhich return RxJS Observables. It will make it easy to use, for example, an ApiService to load the config, and it will probably perform better if the framework does it. By the way, was it not possible in angular 1.X ? thank you!! +1 on this, being able to create objects that can't be created until runtime that are asynchronous in nature would be a huge help.

This would force the entire runtime to become painfully asynchronous. But I would like to have some process that is more angular like.

Needs more up votes. as shown below. Most of the modern approaches are around Observables and hence it makes sense to also update the way we create our providers. This work is licensed under a Creative Commons Attribution-NonCommercial- ShareAlike 4.0 International License. A service is just a singleton object returned by a factory function you registered in a module.

I'm still struggling with this. generally, not everything has to be configured to support the initial loading of the app. These services receive the base url for all the endpoints with a token.

I see no other option but to use a window object (script src="appsettings.js") , because that WILL be available and its the only way i can think of keeping the config separate without too much hassle.