I am injecting service from a super abstract class into our sub classes.
This works fine, except for the Store service.
What I'm doing is the following:
Super Class:
export abstract class GenericClass {
translate: TranslateService;
cdr: ChangeDetectorRef;
someService: SomeService;
otherService: OtherService;
anotherService: AnotherService;
constructor(injector: Injector){
this.translate = injector.get(TranslateService);
this.cdr = injector.get(ChangeDetectorRef);
this.someService= injector.get(SomeService);
this.otherService = injector.get(OtherService);
this.anotherService= injector.get(AnotherService);
}
}
Sub-Class (Component):
export class SubClassComponent {
constructor(injector: Injector){
super(injector);
}
}
This works fine, but with store it doesn't.
When I add Store the same way to the super class, e.g:
Super Class:
export abstract class GenericClass {
...
store: Store<AppState>;
constructor(injector: Injector){
...
this.store = injector.get(Store<AppState>);
}
}
In this case I get the following Error:
ERROR in fox-generic-form.ts(45,30): error TS2348: Value of type 'typeof Store' is not callable. Did you mean to include 'new'?
I tried this with as it suggests in the error:
this.store = injector.get(new Store<AppState>);
How ever in this case I get an error on required arguments in the constructor of Store, and after checking it does require 3 different arguments:
store.d.ts:
constructor(state$: StateObservable, actionsObserver: ActionsSubject, reducerManager: ReducerManager);
I've been searching for this for a while on the net and I can't find a solution, I did find testing scenarios, but those are not what I need for this case of components super-class & Injector.
Any one has an idea of how to use Store with Injector from a super class?
Or how I use these 3 arguments (state$: StateObservable, actionsObserver: ActionsSubject, reducerManager: ReducerManager) with Store?
Should work if you would do injector.get(Store), without the generic type.
Related
I have many endpoints in my app:
/Route1
/Route2
...
/Route99
In a number of these routes, there is some common functionality such as getting specific data from one source such as a local file, or another resource such as a No SQL database or external HTTP endpoint. My problem is that these services need to have a service dependency themselves, and I am not sure that how I have currently done it is the best way to do it in NestJS.
Route1Service - Read a file of data, and return it. This uses the FileSystemService() to wrap all the error handling, different data types, path checking etc., of the NodeJS fs module. The Route1Service then returns this to the Route1Controller
#Injectable()
export class Route1Service {
private FS_:FileSystemService; // defined here instead of constructor, as I do not know how to set it in the constructor via NestJS, or if this is even the best way.
// constructor(private FS_: FileSystemService) { }
// Since I do not set it in the constructor
public DataServiceDI(FsService:FileSystemService):void {
this.FS_ = FsService;
}
public GetData(): string {
const Data:string = this.FS_.ReadLocalFile('a.txt');
return Data;
}
}
Route99Service might do the same thing, but with a different file (b.txt)
#Injectable()
export class Route99Service {
private FS_:FileSystemService;
public DataServiceDI(FsService:FileSystemService):void {
this.FS_ = FsService;
}
public GetData(): string {
const Data:string = this.FS_.ReadLocalFile('b.txt');
return Data;
}
}
This is a contrived example to illustrate my issue. Obviously a basic RouteService could be used, and pass the file name, but I am trying to illustrate the dependent service. I do not know how to define the module(s) to use this dependent service or if I should be doing it this way.
What I have been doing for my definition:
#Module({
controllers: [Route1Controller],
providers: [Route1Service, FileSystemService],
})
export class Route1Module {}
The controller than has the constructor with both Services:
#Controller('route1')
export class Route1Controller
constructor(
private Route1_: Route1Service,
private FsSystem_: FileSystemService
) { }
Now that my controller has the FsSystem service as a separate entity, I need to add a method on my Route1Service, DataServiceDI(), to allow me to pass the FileSystemService as a reference. Then my service can use this service to access the file system.
My question comes down to, is this the best practice for this sort of thing? Ultimately, in my code, these services (FileSystemService, NoSqlService) extend a common service type, so that all my services can have this DataServiceDI() in then (they extend a base service with this definition).
Is this the best approach for longer term maintainability? Is there an easier way to simply inject the proper service into my Route1Service so it is injected by NestJS, and I do not have to do the DI each time?
The current method works for me to be able to simply test the service, since I can easily mock the FileSystemServie, NoSqlService, etc., and then inject the mock.
Should I get the following error:
class.dart:11:11: Error: The getter '_privateID' isn't defined for the class 'Y'.
- 'Y' is from 'class.dart'.
Try correcting the name to the name of an existing getter, or defining a getter or field named '_privateID'.
From the following code?
mixin.dart:
class Mixin {
static int _nextID = 0;
int publicID = _nextID++; // I only need one of these lines
int _privateID = _nextID++; // but this variable is inaccessible
}
class.dart:
import 'mixin.dart';
class X with Mixin {
void run() {
print(publicID); // no error here
}
}
class Y with Mixin {
void run() {
print(_privateID); // Error: _privateID not defined
}
}
void main() {
Y().run();
}
Or is this a bug? If it's not a bug, I'd like to understand why this behavior is reasonable.
When I instead define the mixin in the same file as the above classes, I get no error.
(Dart SDK 2.4.1.)
It is not a bug.
The private field is inherited, but you cannot access it because its name is private to a different library.
Dart's notion of "privacy" is library private names.
The name _privateID in the mixin.dart library introduces a library private name. This name is special in that it can only be written inside the same library.
If someone writes _privateID in a different library, it is a different name, one unique to that library instead.
It is as if private names includes the library URI of the library it is written in, so what you really declare is a name _privateID#mixin.dart.
When you try to read that field in class.dart, you write ._privateID, but because it is in a different library, what you really write is ._privateID#class.dart, a completely different name, and the classs does not have any declarations with that name.
So, if one class needs to access a private member of another class (or mixin, or anything), then the two needs to be declared in the same library, because otherwise they cannot even write the name of that variable.
That is why the code works if you write the mixin in the same library.
If you want to move the mixin to a separate file, but not necessarily a separate library, you can use a part file.
I am newbie for Guice and seeking help for the following use case :
I have developed one package say (PCKG) where the entry class of that package depends on other class like:
A : Entry point class --> #Inject A(B b) {}
B in turn is dependent on C and D like --> #Inject B(C c, D d) {}
In my binding module I am doing :
bind(BInterface).to(Bimpl);
bind(CInterface).to(CImpl);
...
Note I am not providing binding information for A as i want to provide its binding by its consumer class. (this is how the design is so my request is to keep the discussion on main problem rather than design).
Now my consumer class is doing like:
AModule extends PrivateModule {
protected void configure() {
bind(AInterface.class).annotatedWith(AImpl.class);
}
}
Also in my consumer package:
.(new PCKGModule(), new AModule())
Q1. Am i doing the bindings correctly in consumer class. I am confused because when i am doing some internal testing as below in my consumer package:
class testModule {
bind(BInterface).to(Bimpl);
bind(CInterface).to(CImpl)...
}
class TestApp {
public static void main(..) {
Guice.createInstance(new testModule());
Injector inj = Guice.createInstance(new AModule());
A obj = inj.getInstance(A.class);
}
}
It is throwing Guice creation exception.Please help me get rid of this situation.
Also one of my friend who is also naive to Guice was suggesting that I need to create B's instance in AModule using Provides annotation. But i really didn't get his point.
Your main method should look like this:
class TestApp {
public static void main(..) {
Injector injector = Guice.createInjector(new TestModule(), new AModule());
A obj = injector.getInstance(A.class);
}
Note that the Java convention is for class names to have the first letter capitalised.
I'm pretty sure your implementation of AModule isn't doing what you think it's doing either, but it's hard to be certain based on the information you've provided. Most likely, you mean to do this:
bind(AInterface.class).to(AImpl.class)`
There's no need to do anything "special" with A's binding. Guice resolves all the recursion for you. That's part of its "magic".
annotatedWith() is used together with to() or toInstance(), like this:
bind(AInterface.class).to(AImpl.class).annotatedWIth(Foo.class);
bind(AInterface.class).to(ZImpl.class).annotatedWIth(Bar.class);
Then you can inject different implementations by annotating your injection points, e.g.:
#Inject
MyInjectionPoint(#Foo AInterface getsAImpl, #Bar AInterface getsZImpl) {
....
}
It's worth also pointing out that you can potentially save yourself some boilerplate by not bothering with the binding modules (depending how your code is arranged) and using JIT bindings:
#ImplementedBy(AImpl.class)
public interface AInterface {
....
}
These effectively act as "defaults" which are overridden by explicit bindings, if they exist.
I have a class that serves as a model for some data I get from a server. This data starts as an unwieldy xml object where text nodes have attributes so the json format I convert it into does not have simple string values. Instead I have:
#Injectable()
export class FooString {
_attr: string;
value: string;
isReadOnly(): boolean {
return this._attr && this._attr === 'ReadOnly';
}
isHidden(): boolean {
return this._attr && this._attr === 'Hid';
}
}
Then my model is like:
#Injectable()
export class Payment {
constructor(
public FooId: FooString,
public FooStat: FooString,
public FooName: FooString ) { }
}
Everything ends up with the same instance of FooString. How do I get discrete instances for each of them?
I have tried a factory, but it still only creates a single instance:
export let fooStringProvider = provide(FooString, {
useFactory: (): FooString => {
console.log('in foostring factory');
return new FooString();
}
});
new FooString();
new Payment();
;-)
Why using DI when they don't have dependencies and you don't want to maintain single instances per provider. Therefore, just use new.
When to use DI
There are a few criterias when using DI instead of new the right thing:
If you want Angular to maintain and share instances
If you want to work with an interface or base class but then you want to configure from the outside what implementation should actually be used at runtime - like the MockBackend for Http during testing.
If you class has dependencies to instances and/or values provided by DI
If you want to be able to easily test classes in isolation (https://en.wikipedia.org/wiki/Inversion_of_control)
probably others ...
If there are good arguments to use DI, but you also want new instances then you can just provide a factory.
This answer https://stackoverflow.com/a/36046754/217408 contains a concrete example how to do that.
Using DI is usually a good idea. There are IMHO no strong arguments against using DI. Only when none of the above arguments apply and providing factories is too cumbersome, use new Xxx() instead.
Say I've got two taglibs, Foo which does something specific for a particular part of my application, and Util which is shared across the whole thing. I want to do something like this:
class UtilTagLib {
def utilTag = { attrs ->
...
}
}
class FooTagLib {
def fooTag = {
...
out << g.utilTag(att1: "att1", att2: "att2")
...
}
}
However, when I do this, and try to run my unit test for fooTag(), I get:
groovy.lang.MissingMethodException: No signature of method: org.codehaus.groovy.grails.web.pages.GroovyPage.utilTag() is applicable for argument types: (java.util.LinkedHashMap) values: [[att1:att1, att2:att2]]
I tried giving UtilTagLib its own namespace
static namespace = "util"
and changing the call to
out << util.utilTag(...)
but this just gets me
groovy.lang.MissingPropertyException: No such property: util for class: org.example.FooTagLib
Possibly also of note: In the log, I see:
WARN - Bean named 'groovyPagesUriService' is missing.
Obviously, UtilTagLib isn't getting created and injected correctly. How can I fix this?
Solution: add the call
mockTagLib UtilTagLib
to the setUp() (or #Before) method of the test case. This is a method on GroovyPageUnitTestMixin that, somewhat counterintuitively, instantiates the specified tag library -- the real one, not a mock -- and wires it into the Grails application context. It's used internally to set up the actual taglib under test (in this case FooTagLib), but it also works to set up additional collaborator tag libs.
Note that this isn't perfect, since it makes it more of an integration test than a pure unit test -- ideally we would be using a mock UtilTagLib and just testing the interaction.
One approach would be to refactor the line:
out << g.utilTag(att1: "att1", att2: "att2")
in to its own method, say "renderUtilTag(...)", then mock that out in the unit test, e.g.:
FooTagLib.metaClass.renderUtilTag = { /* something */ }
That way you're testing the functionality of FooTagLib only in the unit test, with no dependency on UtilTagLib.