I want to create little CQRS framework for my Typescript Node.js project.
I wish to resolve class by it's name from inversify.js container.
I need something like that:
let x = container.get("Foo");
where Foo is regular class and container is Container object from inversify.js.
Is it possible to do what I want?
You should be able to do the following:
import { Container, injectable } from "inversify";
#injectable()
class Foo {
// ...
}
const container = new Container();
container.bind(Foo).toSelf();
const foo = container.get(Foo);
Or (if foo is the composition root):
import { Container, injectable } from "inversify";
#injectable()
class Foo {
// ...
}
const container = new Container();
const foo = container.resolve(Foo);
Related
I am having trouble implementing singleton, because class marked as #singleton() is being recreated on every resolve().
Here is the example
// Foo.ts This is singleton and and must be created only once
import { injectable, singleton } from "tsyringe";
#injectable()
#singleton()
export class Foo {
constructor() {
console.log("Constractor of Foo");
}
}
// Bar.ts this is Bar and should be created every time. It uses the singleton
import { inject, injectable, Lifecycle, scoped } from "tsyringe";
import { Foo } from "./Foo";
#injectable()
export class Bar {
constructor(#inject("Foo") private foo: Foo) {
console.log("Constractor of Bar");
}
}
// main.ts this is resolving Bar two times.
// expected output:
// Constractor of Foo
// Constractor of Bar
// Constractor of Bar
// Actual output:
// Constractor of Foo
// Constractor of Bar
// Constractor of Foo
// Constractor of Bar
import "reflect-metadata";
import { container } from "tsyringe";
import { Bar } from "./Bar";
import { Foo } from "./Foo";
container.register("Foo", { useClass: Foo });
container.register("Bar", { useClass: Bar });
const instance = container.resolve(Bar);
const instance1 = container.resolve(Bar);
How can I get the desired behavior?
Singleton should be registered as follows
container.register(
"Foo",
{ useClass: Foo },
{ lifecycle: Lifecycle.Singleton } // <- this is important
);
I think you are making your life more difficult. I see a couple of things wrong with what you did and the solution you proposed. Here's the source code for the #singleton() decorator:
function singleton<T>(): (target: constructor<T>) => void {
return function(target: constructor<T>): void {
injectable()(target);
globalContainer.registerSingleton(target);
};
}
First of all, you don't need to decorate with #injectable() because tsyringe already adds it with #singleton().
Finally, if you just don't register Foo and Bar they will automatically be registered as singleton (with the { lifecycle: Lifecycle.Singleton } option already set, of course) in the globalContainer.registerSingleton(target) function.
I am looking for specialized singleton implementation, probably I might be using wrong terminology and hence looking for expert suggestion. Here is my scenario:
There is common code which can be called by ComponentA or ComponentB. I need to push telemetry data from the common code. Telemetry needs to have information that whether this common code get called by ComponentA or ComponentB.
So common code will have just this line of code:
telemetry.pushData(this._area, data);
where this._area tells the telemetry data is getting pushed for which component
I need to push telemetry data from multiple places so it would be good if object got created once and used through out the code lifetime
One option I can think of passing component context to the common code which in mind doesn't look right, hence looking for suggestion what kind of pattern one should use in this case?
This is what I am thinking
// Telemetry.ts file present in shared code
export class Telemetry extends Singleton {
public constructor() {
super();
}
public static instance(): Telemetry {
return super.instance<Telemetry>(Telemetry);
}
public publishEvent(data): void {
if (!this.area) {
throw new Error("Error: Initialize telemetry class with right area");
}
pushtelemetryData(this.area, data);
}
public area: string;
}
// Create Telemetry object from component A
Telemetry.instance().area = "ComponentA";
// Shared code will call telemetry publishEvent
Telemetry.instance().publishEvent(data);
Thanks
It's not a good pattern to use in TypeScript where you would generally inject dependencies.
If you must absolutely do it then you can do it by faking it somewhat:
namespace Telemetry {
var instance : SingletonSomething;
export function push(data: Any) : void {
if (instance == null) {
instance = new SingletonSomething();
}
instance.push(data);
}
class SingletonSomething() { ... }
}
and then you could call
Telemetry.push(data);
You can imitate the singleton pattern in typescript easily:
class Telemetry {
private static instance: Telemetry;
public static getInstance(): Telemetry {
if (Telemetry.instance == null) {
Telemetry.instance = new Telemetry();
}
return Telemetry.instance;
}
...
}
If you have your code in some sort of closure (module, namespace, etc) then you can replace the static member with:
let telemetryInstance: Telemetry;
export class Telemetry {
public static getInstance(): Telemetry {
if (telemetryInstance == null) {
telemetryInstance = new Telemetry();
}
return telemetryInstance;
}
...
}
But then you can also replace the static method with:
let telemetryInstance: Telemetry;
export function getTelemetryInstance(): Telemetry {
if (telemetryInstance == null) {
telemetryInstance = new Telemetry();
}
return telemetryInstance;
}
export class Telemetry {
...
}
At this point, in case you are using some sort of closure, you might ask yourself if you really need the class at all?
If you use this as a module:
// telemetry.ts
export interface TelemetryData {
...
}
export function pushData(data: TelemetryData): void {
...
}
Then you get exactly what you're looking for, and this is more of the "javascript way" of doing it.
Edit
In the telemetry module there's no need to know the users of it.
If the Telemetry.pushData function needs to have information about the object that called it then define an interface for it:
// telemetry.ts
export interface TelemetryData {
...
}
export interface TelemetryComponent {
name: string;
...
}
export function pushData(data: TelemetryData, component: TelemetryComponent): void {
...
}
Then in the other modules, where you use it:
// someModule.ts
import * as Telemetry from "./telemetry";
class MyComponent implement Telemetry.TelemetryComponent {
// can also be a simple string property
public get name() {
return "MyComponent";
}
fn() {
...
Telemetry.pushData({ ... }, this);
}
}
2nd Edit
Because you are using a module system, your module files are enough to make singletons, there's no need for a class to achieve that.
You can do this:
// telemetry.ts
let area: string;
export interface TelemetryData {
...
}
export function setArea(usedArea: string) {
area = usedArea;
}
export function pushData(data: TelemetryData): void {
...
}
Then:
Telemetry.setArea("ComponentA");
...
Telemetry.publishEvent(data);
The telemetry module will be created only once per page, so you can treat the entire module as a singleton.
Export only the functions that are needed.
The scenario: I have two derived classes that both extend the ActionBase class as follows. I want to use DI for both derived classes. But both classes have different dependencies. That should be possible, right? So what am I doing wrong? In both cases the injected instances/modules are 'undefined'. Any help/hint appreciated.
/*
* Base class for Actions
*/
export class ActionBase {
type;
constructor(type) {
this.type = type;
}
}
/*
* Derived Class: InsertAction
*/
import {inject} from 'aurelia-framework';
import {ActionBase} from './ActionBase';
import {PomManager} from '../manager/PomManager';
#inject(PomManager)
export class InsertAction extends ActionBase {
pomManager;
constructor(pomManager) {
super("insert");
this.pomManager = pomManager;
console.log("[InsertAction:constructor] pomManager: ", this.pomManager); // undefined
}
}
/*
* Derived Class: RenderAction
*/
import {inject} from 'aurelia-framework';
import {ActionBase} from './ActionBase';
import {AnotherManager} from '../manager/AnotherManager';
#inject(AnotherManager)
export class RenderAction extends ActionBase {
anotherManager;
constructor(anotherManager) {
super("render");
this.anotherManager = anotherManager;
console.log("[RenderAction:constructor] anotherManager: ", this.anotherManager); // undefined
}
}
It is supported. Look at this working example where Action1 and Action2 extend BaseAction and each take different dependencies.
Here's an example: https://gist.run?id=0efabf77c649f41981dcde753fdc542c
app.js
import {inject} from 'aurelia-dependency-injection'
import {Action1, Action2} from './classes'
#inject(Action1, Action2)
export class App {
constructor(a1, a2){
this.message = "look at console output";
console.log("a1", a1.dep.constructor.name);
console.log("a2", a2.dep.constructor.name);
}
}
classes.js
import {inject} from 'aurelia-dependency-injection'
export class Action1Dependency {}
export class Action2Dependency {}
export class ActionBase{
}
#inject(Action1Dependency)
export class Action1 extends ActionBase{
constructor(dep){
super();
this.dep = dep;
}
}
#inject(Action2Dependency)
export class Action2 extends ActionBase{
constructor(dep){
super();
this.dep = dep;
}
}
I have a file a.ts which contains a class A inside a module:
module moduleA {
export class A {
}
}
export = moduleA.A;
And another file b.ts which imports class A:
import A = require('a.ts');
class B {
// This leads to an error: Cannot find name 'A'
private test: A = null;
constructor() {
// But this is possible
var xyz = new A();
}
}
Interestingly, Typescript shows an error when I want to use A as a type in B. However, instantiating A does not lead to an error.
Can anybody explain me, why this is like that?
Thank you very much!
The use of the namespace module moduleA is not necessary... you can do this...
the keyword module is synonymous with namespace (C#) now... best practice is to use the ES6 style module structure which is basically each file is a module and export what you need and import what you need from elsewhere.
// a.ts
export class A {}
// b.ts
import { A } from './a';
class B {
private test: A = null; // will not error now
constructor () {
var xyz = new A();
}
}
Note: this is based upon TypeScript v1.5+
It looks like this is not allowed. requireJS is throwing an error on the following (this post is different as it was resolved with internal modules):
element.ts:
import runProperties = require('./run-properties');
export class Element {
public static factory (element : IElement) : Element {
switch (element.type) {
case TYPE.RUN_PROPERTIES :
return new runProperties.RunProperties().deserialize(<runProperties.IRunProperties>element);
}
return null;
}
}
run-properties.ts:
import element = require('./element');
export class RunProperties extends element.Element implements IRunProperties {
}
No, modules can't have circular dependencies unless they are in the same file. Each file is being processed in sequence, synchronously, so the full file definition (including all of the exports for example) hasn't been completed when it goes to second file, which immediately tries to require/reference the first file, and so on.
Normally, you can break a circular dependency by introducing an interface or base class into a common definition file(s) (basically interfaces only) and having the other files use that as a common "interface" rather than directly referencing the classes. This is a typical pattern in many platforms.
I have same issue, I was able to fix it by creating factory class that allows registration of child classes and used Generics for instantiation.
Reference: https://www.typescriptlang.org/docs/handbook/generics.html#using-class-types-in-generics
See sample code below:
Base Class (abstract.control.ts)
export type AbstracControlOptions = {
key?:string;
}
export abstract class AbstractControl {
key:string;
constructor(options:AbstracControlOptions){
this.key = options.key;
}
}
Parent Class (container.ts)
import { AbstractControl, AbstracControlOptions } from './abstract.control';
import { Factory } from './factory';
export { AbstracControlOptions };
export abstract class Container extends AbstractControl {
children: AbstractControl[] = [];
constructor(options: AbstracControlOptions) {
super(options);
}
addChild(options: { type: string }) {
var Control:any = Factory.ControlMap[options.type];
if (Control) {
this.children.push(Factory.create(Control, options));
}
}
}
I don't have to import the child classes any more, because I'm using factory.ts to instantiate the child classes.
Factory Class(factory.ts)
import {AbstractControl, AbstracControlOptions} from './abstract.control';
type ControlMap<T extends AbstractControl> = {
[type:string]:T
};
export class Factory{
static ControlMap: ControlMap<any> = {};
static create<T extends AbstractControl>(c: { new ({}): T; }, options: AbstracControlOptions): T {
return new c(options);
}
}
Although class constructor seems to be called at c: { new ({}): T } but it does not actually calls it. But gets the reference to the constructor via new operator. The parameter {} to the constructor in my case is required because the base class AbstractControl requires it.
(1) Child Class(layout.ts)
import { Factory } from './factory';
import { Container, AbstracControlOptions } from './container';
export type LayoutlOptions = AbstracControlOptions & {
type:"layout";
}
export class Layout extends Container {
type: string = "layout";
constructor(options:LayoutlOptions) {
super(options);
}
}
Factory.ControlMap["layout"] = Layout;
(2) Child Class(repeater.ts)
import { Factory } from './factory'
import { Container, AbstracControlOptions } from './container';
export type RepeaterOptions = AbstracControlOptions & {
type: "repeater";
}
export class Repeater extends Container {
type: string = "repeater";
constructor(options:RepeaterOptions) {
super(options);
}
}
Factory.ControlMap["repeater"] = Repeater;