I'm trying to make a NestJS Library for an API I want to access. I split it off into its own library where the main module is a dynamic module that takes the baseUrl for the server it will be connecting to. I then have a second "child" api-section module that will actually be making the api calls. I need a way to pass that baseUrl into the api-section while also exporting the api-section service from the api-library to use in the main apps app.module. The modules are split this way since there will be many "child" modules to access different parts of the API as its very big.
Currently this leads to a circular dependency issue, with the cli suggesting I use a forwardRef. I've tried adding a forwardRef to both the ApiSectionModule import in ApiLibraryModule and vice versa but that leads to another error "TypeError: metatype is not a constructor"
I feel like this whole thing is just the wrong overall pattern, but not sure how else to approach it.
Sample repo:
https://github.com/computebender/libsample
Related
Context
I am currently working on a Typescript Lambda project where we are planning to refactor our code to make use of dependency injection using the Tsyringe library. We have a typical MVC structure for projects except instead of the Repo/Database layer we have a proxy layer which calls a third-party service over the rest API to fetch the required data.
The catch is that the proxy layer will have a single interface defined and it will have multiple implementations among which one needs to be injected depending upon the business decision. For example AuthProxy is an interface which contains a login method, and it has two different implementation classes KeycloakAuthProxyImpl and AuthZeroAuthProxyImpl. These two implementations will be in 2 separate folders say AuthZero and KeyCloak and while building we pass an argument like --folderName so only one implementation will be available in runtime for dependency injection.
The problem
The problem we are facing with Tsyringe (I have evaluated some other libraries too) is that interface-based dependency injection needs explicit token-based registration with ioc-container in the main.ts page(In my case, the handler function file). So as per theory, I should be registering it as follows.
.
But in our case, this is not possible. Because say we are building it as --keycloak as an argument, then AuthZearoAuthProxyimpl will be ignored while compiling and hence the code will break in line 14 at runtime.
We tried to move that dependency registration logic to the corresponding implementation class so that each implementation class will be self-contained and isolated so that there won't be any runtime issues. But then these are not even being registered for dependency injection and we get an error saying Attempted to resolve unregistered dependency token: "AuthProxy". This is expected as per the file loading of javascript.
KeycloakImpl class.
.
We even tried using #registry decorator which can be found commented in the images, but it also didn't make any difference.
Even though I haven't tried any other dependency injection libraries of Typescript, from my little research, most of them follow more or less the same pattern for interface-based dependency injection and I am anticipating the same issue in those also. Is there any other workaround through which I can resolve this issue, or is it even possible with typescript?
PS: I don't have much expertise in js and typescript, the above keywords are based on my experience with spring and java. Please ignore if I have misused any js specific terminologies while explaining the issue.
Code and project structure
I had similar problems with tsyringe and I found a much better approach.
Here is how I would solve this with a different DI lib iti and also remove many lines of code:
import { createContainer } from "iti"
import express from "express"
// import other deps
const container = createContainer()
.add({
authProxy: () =>
Math.random() > 0.5
? new KeycloakAuthProxyImpl()
: new AuthZearoAuthProxyImpl(),
})
.add((ctx) => ({
authService: () => new AuthServiceV3(ctx.authProxy),
}))
.add((ctx) => ({
server: () => {
const app = express()
app.all("/login", async (req, res) => handler(req, ctx.authService))
return app
},
}))
// start your server / lambda
const server = container.get("server")
server.listen(3000)
I've also refactor other parts of the app and got rid of singletons and made code IMO a bit simpler to read
I’ve created an interactive playground with a mock your app:
https://stackblitz.com/edit/json-server-ntssfj?file=index.ts
Here are some links to the lib:
https://github.com/molszanski/iti
https://itijs.org/
I am building a Sails.js application using sails 1.2.3, node 10.15. I want to include a javascript module in my api/helpers/* directory, without sails automatically using it to try to create a helper. I.e. I have javascript objects that use helpers and are used in a helper, but are not helpers themselves; as in this image, where the module 'rules' is imported into the create-rule helper and the objects exported by this module are used within the helper.
By default, sails tries to load each file in the helpers/* directory as a helper, and throws if the underlying implementation does not match that of a valid helper:
ImplementationError: Failed to load helper `create-rule/rules/foo/index` into a Callable! Sorry, could not interpret "index" because its underlying implementation has a problem:
------------------------------------------------------
• Missing the `fn` property.
------------------------------------------------------
Hoping someone can help out! Let me know if more info is needed. Thanks in advance!
I don't quite understand what you are trying to do. In my humble opinion I would grab all object constructors and placed them as a single file in api/services. That will make it automatically available in all controllers. I would not allow my object's methods to use helpers by them selves (I even think you can't, at least easily). Then when you need a helper to use your object, just pass it as parameter. Anyway, again, in my humble opinion; you are structuring your code to fit all inside /helpers and that will make it extremely hard to develop. Let assume you manage to make it work all inside /helpers, only you without exception, will be able to understand what it does or how it works. Doesn't seem as a good idea.
I've been looking to develop a method for loading modules and/or components into an AOT-compiled Angular 4 application and been stymied by a variety of solutions that never quite seem to get me where I want to be.
My requirements are as such:
My main application is AOT compiled, and has no knowledge of what it is loading until runtime, so I cannot specifically identify my dynamic module as an entry component at compile time (which is explicitly necessary for the 'dynamic' component loading example presented on Angular.io)
I'd ideally love to be able to pull the code from a back end database via a GET request, but I can survive it simply living in a folder alongside the compiled site.
I'm using Webpack to compile my main application, breaking it into chunks - and so a lot of the SystemJS based solutions seem like dead ends - based on my current research, I could be wrong about this.
I don't need to know or have access to any components of my main application directly - in essence, I'd be loading one angular app into another, with the dynamically loaded module only perhaps having a few tightly controlled explicit interface points with the parent application.
I've explored using tools like SystemJsNgModuleLoader - which seems to require that I have the Angular compiler present, which I'm happy to do if AOT somehow allowed me to include it even if I'm not using it elsewhere. I've also looked into directly compiling my dynamic module using ngc and loading the resulting ngfactory and compiled component/module, but I'm not clear if this is at all possible or if so - what tools Angular makes available to do so. I have also seen references to ANALYZE_FOR_ENTRY_COMPONENTS - but can't clearly dig up what the limitations of this are, as first analysis indicates its not quite what I'm looking for either.
I had assumed I might be able to define a common interface and then simply make a get request to bring my dynamic component into my application - but Angular seems painfully allergic to anything I try to do short of stepping outside of it alltogether and trying to attach non-angular code to the DOM directly.
Is what I'm trying to do even possible? Does Angular 2+ simply despise this kind of on the fly modification of its internal application architecture?
I think I found an article that describes exactly what you are trying to do. In short you need to take over the bootstrap lifecycle.
The magic is in this snippet here.
import {AComponentNgFactory, BComponentNgFactory} from './components.ngfactory.ts';
#NgModule({
imports: [BrowserModule],
declarations: [AComponent, BComponent]
})
export class AppModule {
ngDoBootstrap(app) {
fetch('url/to/fetch/component/name')
.then((name)=>{ this.bootstrapRootComponent(app, name)});
}
bootstrapRootComponent(app, name) {
const options = {
'a-comp': AComponentNgFactory,
'b-comp': BComponentNgFactory
};
https://blog.angularindepth.com/how-to-manually-bootstrap-an-angular-application-9a36ccf86429
I'm trying to load multiple modules on the fly via chokidar (watchdog) using Meteor 1.6 beta, however after doing extensive research on the matter I just can't seem to get it to work.
From what I gather require by design will not take in anything other than static strings, i.e.
require("test/string/here")
Since if I try:
var path = "test/string/here"
require(path)
I just get Error: Cannot find module, even though the strings are identical.
Now the thing is I'm uncertain how to go on about this, am I really forced to either use import or static strings when using meteor or is there some workaround this?
watchdog(cmddir, (dir) => {
match = "." + regex_cmd.exec(dir);
match = dir;
loader.emit("loadcommand", match)
});
loader.on('loadcommand', (file) => {
require(file);
});
There is something intrinsically weird in what you describe.
chokidar is used to watch actual files and folders.
But Meteor compiles and bundles your code, resulting in an app folder after build that is totally different from your project structure.
Although Meteor now supports dynamic imports, the mechanism is internal to Meteor and does not rely on your actual project files, but on Meteor built ones.
If you want to dynamically require files like in Node, including with dynamically generated module path, you should avoid import and require statements, which are automatically replaced by Meteor built-in import mechanism. Instead you would have to make up your own loading function, taking care of the fact that your app built folder is different from your project folder.
That may work for example if your server is watching files and/or folders in a static location, different from where your app will be running.
In the end, I feel this is a sort of XY problem: you have not described your objective in the first place, and the above issue is trying to solve a weird solution that does not seem to fit how Meteor works, hence which may not be the most appropriate solution for your implicit objective.
#Sashko does a great job of explaining Meteor's dynamic imports here. There are also docs
A dynamic import is a function that returns a promise instead of just importing statically at build time. Example:
import('./component').then((MyComponent) => {
render(MyComponent);
});
The promise runs once the module has been loaded. If you try to load the module repeatedly then it only gets loaded once and is immediately available on subsequent requests.
afaict you can use a variable for the string to import.
Based on recommendations for the preparation for Ember 2.0...
• In general, replace views + controllers with components
• Only use controllers at the route level...
...we're supposed to eschew Controllers and Views in favor of Components. I haven't been able to figure out and/or understand how to generate Components that aren't direct parents of the components folder, i.e. components/component-name.js.
My current controllers folder looks something like:
/controllers
/account
index.js
edit.js
/business
index.js
Basically, there are sub-folders that group logic based on the sections of the application. How do I accomplish this with just components?
Seeing that components must have a "-" in them, I tried, but get an error...
ember generate component account/index-module.js
You specified "account/index-module.js", but due to a bug in Handlebars (< 2.0) slashes within components/helpers are not allowed.
Do all components have to be like
components
account-index.js
account-new.js
business-index.js
i.e. all in the same folder? This will start to get out of hand with the addition of what I actually consider to be components (things like video-viewer.js, text-editor.js, radio-button.js).
I would really like to have components in sub-folders, but unsure how to do this.
components
/media
/audio
audio-player.js
/video
video-player.js
/text-editing
text-editor.js
editor-toolbar.js
My components folder is already gross and I just got started:
Is it okay to leave the account/business logic in Controllers (seeing that it does say you should only use controllers at the Route level)?
I'm really confused about this "all components, all the time" convention.
Ok, so I had the same problem and as of ember 1.9-beta.3 (that's the version I tested). It is possible to have components nested under resource directories.
That means that you can have a "user" route or resource. And let's say you have a component which you only want to use with the user resource, so you want to put the component under the resource directory.
The way to do it is to put the component under the resource directory app/pods/user/component-name/template.hbs. The important part is to remember that components must have a dash in their name. It can't be just .../user/component it has to be .../user/component-name with a dash. Then you can use the component as {{user/component-name}} in your templates.
Also I think this is only possible when you're using the pod structure.
Ok, I think this question/answer needs a bit of an update for 2019. I have been using Ember for all of about a month, and my components folder has already become a pigpen. And the tutorial and main API docs don't really cover how to organize your components.
So I did a search of course. And the only answers I could find (like this one) are from around 2014-2015, and don't reflect modern Ember. I was about to accept my fate when I found this in the Ember syntax conversion guide.
(Note to the Ember folks: This is an important issue, one that almost every new user will encounter. It should feature a bit more prominently in the documentation. Maybe not the tutorial, but definitely in Components section)
You can in fact generate components under a sub-folder in Ember as such:
$ ember generate component foo/bar-baz
installing component
create app/components/foo/bar-baz.js
create app/templates/components/foo/bar-baz.hbs
installing component-test
create tests/integration/components/foo/bar-baz-test.js
So that's great, the files are created under components/foo and templates/components/foo. And to resolve the name of the component for use in another template, you can use either the old style syntax:
{{foo/bar-baz }}
Or the new style angle bracket syntax:
<Foo::BarBaz />
As the assertion suggests this is due to Handlebars 1.x, and will be available soon.
Ember 1.9 beta builds currently support this, though I'm not positive if ember-cli's resolver would work with it right now. You can read more about Handlebars 2.0 here.
Using a pods structure will also help with organization, and I believe is going to be the recommended strategy going forward.
For now, I'd suggest not to worry about it! Remember the transition plan will be smooth, and as the official releases come out for Ember and Ember CLI, you'll get deprecation warnings.