I Can take instance of service using this example:
export class GetEntityDomainService {
constructor(private readonly moduleRef: ModuleRef) { }
getEntity(): void {
const myObject = this.moduleRef.get(MyClassName);
}
}
but how could I invoke a service instance outside of a class object
where I don't have a handle to moduleRef:
here is example from angular:
const injector = ReflectiveInjector.resolveAndCreate(providers);
const widgets: WidgetService = injector.get(WidgetService);
https://kevinphelps.me/blog/2017-01-17-using-angular-dependency-injection-in-node
whether is it possible to download an instance of the service without needing a moduleRef?
Thanks
Piotr
There are several reasons
sometimes I need to inject a service in a function, then I have to pass moduleRef to this function to make it possible
The second example is Command and Events -
for example I create such an action, then I pass parameters to send to handler,:
this.dispach(new Command (parameters ...))
Currently my actions know from which module they are triggered and in which module their handler is - so I won't send actions between wrong areas of the system (layers, dependencies). I check all this when executing
this.dispach (new Command ())
now I have to write such a dispatch as follows:
this.dispach (new Command (this.moduleRef, ... other parameters))
could I create a moduleRef from the code?, it would facilitate the process of creating an action and eliminate the need to pass moduleRef
but I don't know if it will help me
as I analyzed DI nest, it works differently from angular
The service knows where it was declared and when it injects something in it, it uses the tokens declared in this module
I suppose I will only be able to inject general scope
Related
In offical document about authorization, i follow this guide and use casl lib
Let's assume that if i want to validate the request man is the owner of an article, i must get the article data from the database, and compare userId between user and article.userId, so i must inject a repoistory dependency like this
#Injectable()
export class DeleteHolePolicyHandler implements IPolicyHandler {
#Inject()
private readonly treeholeDaoService: TreeholeDaoService
async handle(ability: AppAbility, req: Request) {
const hole = await this.treeholeDaoService.findById(req.body.id)
return res
}
}
but i got an error, it shows me this.treeholeDaoService is undefined.
so what should i do that can make it work?
this is reproduce link
You can't inject dependencies since it's an in-place property declared using new. As stated in the docs:
Since we must instantiate the policy handler in-place using the new keyword, ReadArticlePolicyHandler class cannot use the Dependency Injection. This can be addressed with the ModuleRef#get method (read more here). Basically, instead of registering functions and instances through the #CheckPolicies() decorator, you must allow passing a Type<IPolicyHandler>. Then, inside your guard, you could retrieve an instance using a type reference: moduleRef.get(YOUR_HANDLER_TYPE) or even dynamically instantiate it using the ModuleRef#create method.
I started migrating a project from typeorm to MikroORM and I've been facing an issue when calling the same ( or different ) repository more than once. The error is as follows:
ValidationError: Using global EntityManager instance methods for context specific actions is disallowed. If you need to work with the global instance's identity map, use 'allowGlobalContext' configuration option or 'fork()' instead.
A more detailed explanation is:
I am using NestJS
DB is postgreSQL
GRPC communication for this specific service ( not sure if that matters )
Wrapping repository calls in rxjs observables: e.g. from(this.userRepository.findOne({id: user.id})
Now, I've read through the documentation and other issues here and on github mainly regarding the EntityManager and the RequestContext. I've added the #UseRequestContext() annotation on my controller ( and injected the private readonly orm: MikroORM, instance in the constructor ):
#GrpcMethod('UsersService', 'Login')
#UseRequestContext()
login(user: UserLogin): Observable<UserResponse> {
return this.userService.login(user);
}
The service itself calls userRepository.find... and via debug I can see the executed query and the result is fetched, however I have another call to the roleRepository later on down the line. This call fails with the error above. I've played around with it and it seems like even if I try to call the same userRepoistory.find... for a second time it will fail again: e.g.:
loginUser(user: UserLogin) {
return this.getUserById(user.id).pipe(
switchMap(() => this.getUserById(user.id)),
);
}
If I do the following inside the getUserById method however, it works like a charm:
getUserById(id: string): Observable < User > {
const emFork = this.em.fork();
return from(emFork.findOne(User, {
userId: id
}));
Basically what I am trying to understand is:
It says in the documentation that the function marked with #UseRequestContext() should not return anything, however when placing it on the Grpc method it works ( at least for the first repository call ). If I remove it I get the same error before calling any repositories. Am I using it correctly?
If the forking of the EntityManager is the correct approach, wouldn't that make creating Repository classes and injecting them obsolete? Also isn't forking it each time going create a lot of instances?
It's obvious I am lacking understanding on how this context works, so an explanation would be greatly appreciated!
Also, any other hints/tips are welcome!
Thank you for your time :)
I used loopback 4 to bootstrap my API application and developed some parts of it.
Now I'm trying to access repositories outside the controllers and tried everything I could but didn't help. None of my searches did too. For example I have a controller in which I can access repo such way.
constructor(
#repository(UserRepository) public userRepository: UserRepository){}
But if it isn't a controller it won't work and I found out I had a wrong understanding about #repository and #inject decorators.
My Case:
I want to run a cron-job to perform an update operation on database every day at a specific time.
The thing is I think I should create a service or something like that to expose database operations so it can be accessible anywhere.
The issue you're trying to tackle comes down to dependency injection. It's described at https://loopback.io/doc/en/lb4/Dependency-injection.html but that article does not explain how to create a separate class that works with dependency injection.
In short, in order to perform the dependency injection through decorators, LoopBack needs to be the one to construct the class you're writing, so that it can pick what you need from its Context. So, instead of writing new ClassSomething, it has to be #inject(ClassSomething) or #service(ClassSomething), and those decorators only work in a class also instantiated by LoopBack. In other words, your class has to be in the "call tree" from the original application class (application.ts) for dependency injection to work.
The easiest way to do what you want to do is to use LoopBack's Cron component: see https://loopback.io/doc/en/lb4/Running-cron-jobs.html. You could convert your class to a CronJob if it has no other purpose, or let the CronJob create an instance of your class. In the latter case, you need to bind your class to the application Context so that the CronJob can access it through decorators. You can do so in two ways:
Convert your class to a Service (see https://loopback.io/doc/en/lb4/Service.html and https://loopback.io/doc/en/lb4/Service-generator.html). If what your class does can be thought of as a service, this is the way to go.
Inject your class with: #service(MyServiceClass) myService: MyServiceClass
Directly bind your class to the application context, in application.ts:
this.bind('MyClass').toClass(MyClass);
Inject your class with: #inject(MyClass) myClass: MyClass
The latter option is not best practice AFAIU as it does not adhere to IoC-principles (https://en.wikipedia.org/wiki/Inversion_of_control) - basically, by hard-coding the class binding in the application class, it is not exactly modular. When your class is converted to a service (and placed in src/services), it will automatically be added to the Context, meaning you can inject it everywhere using #service().
I also experience the same(cron word). I couldn't find any solution still in the documentation. But still, I have achieved this in this way.
just call repository as like class with dependency in it. do this in your index.ts file where you start the application.
async function startCronJobs(app: SawLoopbackApplication) {
const userRepo = app.repository(UserRepository);
const userRepoInstance = await userRepo.getValue(app);
const cron = new CronComponent(userInstance);
//---- Exicute your cron here
new CronJob('0 6 * * *', function () {
cron.sendMorningMail()
}).start();
//---- Exicute your Second Cron
new CronJob('0 8 * * 1', function () {
cron.weeklyAppraisalsToAgent()
}).start();
}
call your cron in the functional component and execute a raw query to get the details from DB etc...
import {MysqlDataSource} from '../../datasources'
const query = `select * from accounts where IP="${ipAddress}" ORDER By
createdAt DESC Limit 1`
const dataSource = new MysqlDataSource()
const accountDetails = await dataSource.execute(query)
console.log(accountDetails)
instead of a raw query. call your repository from the function component below
import {MysqlDataSource} from '../datasources'
import {ContactUsUserDetailsRepository} from '../repositories'
const contactUsUserDetailsRepository = new ContactUsUserDetailsRepository(new MysqlDataSource)
function saveContactDetails(){
const payload={UID:"Unique ID",name:"Durai"}
await contactUsUserDetailsRepository.create(payload)
}
I would prefer 2 because, if you have a lot of imports in your cron class constractor you need to pass all of them while calling a function like in the 3rd point.
Have fun:)
I have this node api app built using express and typescript.
Before starting the server I am initializing the static variable of the Configuration Class with the required config.
But when I use this static variable in a separate Typescript class across application, I keep getting this undefined error.
Is there something which I am missing here?
server.ts
// Initialize Config
Configuration.initAppConfig();
server.start()
app.config.ts
import config from 'config';
const packageInfo = require('../../package.json');
// other imports
export class Configuration {
static appConfig: IAppConfig;
static initAppConfig() {
Configuration.appConfig = <IAppConfig>{
appName: packageInfo.name,
db: <IDbConfig>config.get("db"),
server: <IServerConfig>config.get("server")
}
//prevent it from getting reassigned
Object.freeze(this.appConfig);
}
}
db.config.ts
import { Configuration } from './app.config';
export class DBConfig{
private static logger = LoggerFactory.getLogger(Configuration.appConfig.appName);
// other stuffs
}
Error
private static logger = LoggerFactory.getLogger(Configuration.appConfig.appName);
^
TypeError: Cannot read property 'appName' of undefined
PS:
It works if I remove static from logger. Any reason why this is happening? I am literally banging my head. :|
//works
private logger: Logger = LoggerFactory.getLogger(Configuration.appConfig.appName);
//Not working - appName of undefined error
private static logger: Logger = LoggerFactory.getLogger(Configuration.appConfig.appName);
The main difference between the version that works (without the static) and the version that doesn't work (with static) is on the timing of when the member is being initialized.
When the member is not static, it is only initialized when some code (not displayed here) is creating an instance of the containing class (DBConfig). By that time, Configuration.appConfig has already been initialized.
When the member is static, it is initialized much earlier, at a stage when Configuration.appConfig is not initialized yet.
One way to overcome this is to ensure that Configuration.appConfig is initialized first, for example by using a synchronous call (or some other solutions, depending on the structure of your code segments not shown here).
Regarding instance/static, instance methods belong to the instance of a class (objects created with the “new” keyword) and static methods extend the class template, meaning they belong to the class itself and are accessible to all the instances (objects) of the class.
So, if you try to call the instance method from a the static method means trying to access the instance method of an already existing instance inside the static method. In other words, you need to create/have an instance inside the scope of your static method to be able to access its instance method.
I am not sure if instance/static concept as explained here applies purely this way in typescript, but calling an instance from a spare static method does not seem a good idea taking into account the general understanding of static.
I am trying to implement a task using the cakephp shell for my application. The task involves running a long running process (hence the need to use the shell).
The function requires me to use a function inside a Component called CommonComponent
Unfortunately whenever i try to include the component i get the following error
PHP Fatal error: Class 'Component' not found in /var/www/nginx-test/app/Controller/Component/CommonComponent.php
Here is the CronShell Class which is being called
class CronShell extends AppShell {
public function main() {
$this->out('Hello world.');
// $this->out(phpinfo());
}
public function test()
{
$this->out('Before Import');
App::import('Component', 'Common');
$this->out('Import complete');
// $this->Common=ClassRegistry::init('CommonComponent');
$this->Common =new CommonComponent();
$this->out('Initialization complete');
$this->Common->testCron();
$this->out('FunctionCall complete');
//$this->Common->saveCacheEntry("name","value");
}
}
The CommonComponent class is stored as app/Controller/Component/CommonComponent.php and is as follows
class CommonComponent extends Component
{
function testCron()
{
$this->out('Hello world from Component.');
}
}
Any ideas?
I had to do this recently with MTurk component I wrote. My final solution was using a lib instead of a component. Then I had the component access the lib so I could use the methods from both a component and from shell.
However, here is code that WILL allow you to load a component from a shell.
<?php
App::uses('AppShell', 'Console/Command');
App::uses('ComponentCollection', 'Controller');
App::uses('Controller', 'Controller');
App::uses('MTurkComponent', 'Controller/Component');
class ProcessCompletedTask extends Shell {
public function execute() {
$this->out("Processing...\n");
$collection = new ComponentCollection();
$this->MTurk = new MTurkComponent($collection);
$controller = new Controller();
$this->MTurk->initialize($controller);
$this->MTurk->processHITs();
$this->out("Complete\n");
}
}
What you import into the Shell should be code from within your Apps Lib
the component can also make use of the Lib code - but you'll not need to do a load of tedious stuff
if you set it up right you'll make you app cleaner
if you import the component you'll need to pass it a component collection and so you'd have to make that from witin shell not that your use it (or if you do you must be doing it wrong)
Have you tried App::uses('Component', 'Controller'); at the top of your file, ev. before import of CommonComponent? Then I guess you need to do what sam says, or you could use the $this->Controller->Components->load('CommonComponent') but for that you need to construct the Controller class.
I believe that it is semantically wrong to share functionality between controllers and shells.
If you require common functionality, it is clearer and neater to put it in a separate class, place this class in your vendors folder and then import the code into both the controller and the shell.
In addition, this approach does not prevent you from creating components and tasks that use the core functionality and then share these components and tasks between your controllers and shells.