Lazy evaluated property injection decorators
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README.md

inversify-inject-decorators

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Lazy evaluated property injection decorators.

Motivation

Some frameworks and libraries take control over the creation of instances of a given class. For example, React takes control over the creation of instances of a given React component. This kind of frameworks and libraries prevent us from being able to use constructor injection and as a result they are not easy to integrate with InversifyJS.

InversifyJS also provides support for property injection but it also requires the instances of a class to be created by InversifyJS.

The decorators included in this library will allow you to lazy-inject properties even when the instances of a class are not created by InversifyJS.

This library allows you to integrate InversifyJS with any library or framework that takes control over the creation of instances of a given class.

Installation

You can install inversify-inject-decorators using npm:

$ npm install inversify inversify-inject-decorators reflect-metadata --save

The inversify-inject-decorators type definitions are included in the npm module and require TypeScript 2.0.

⚠️ Please note that this library requires support for the ES6 Symbol. You can use the es6-symbol polyfill as a work arround.

Please refer to the InversifyJS documentation to learn more about the installation process.

Caching vs Non Caching Behaviour

By default, the lazy injection mechanism implemented by this will cache all requests to the underlying container. This means that rebinding or unbinding services to/from service identifiers will not be reflected in the instances into which these services have been injected into. The same holds true for scenarios where you dynamically load/unload container modules and thus either add or remove bindings from your container.

To overcome this limitation, one can now pass an additional boolean parameter to getDecorators(container: Container, doCache = true). When set to false, services resolved from the container will no longer be cached and will always be resolved from the container directly, e.g.

import { Container } from "inversify";
import getDecorators from "inversify-inject-decorators";

const container: Container = new Container();
const { lazyInject } = getDecorators(container, false);

Basic property lazy-injection with @lazyInject

The following example showcases how to inject into a property using the @lazyInject decorator:

import getDecorators from "inversify-inject-decorators";
import { Container, injectable, tagged, named } from "inversify";

let container = new Container();
let { lazyInject } = getDecorators(container);
let TYPES = { Weapon: "Weapon" };

interface Weapon {
    name: string;
    durability: number;
    use(): void;
}

@injectable()
class Sword implements Weapon {
    public name: string;
    public durability: number;
    public constructor() {
        this.durability = 100;
        this.name = "Sword";
    }
    public use() {
        this.durability = this.durability - 10;
    }
}

class Warrior {
    @lazyInject(TYPES.Weapon)
    public weapon: Weapon;
}

container.bind<Weapon>(TYPES.Weapon).to(Sword);

let warrior = new Warrior();
console.log(warrior.weapon instanceof Sword); // true

Named property injection with @lazyInjectNamed

The following example showcases how to inject into a named property using the @lazyInjectNamed decorator:

import getDecorators from "inversify-inject-decorators";
import { Container, injectable, named } from "inversify";

let container = new Container();
let { lazyInjectNamed } = getDecorators(container);
let TYPES = { Weapon: "Weapon" };

interface Weapon {
    name: string;
    durability: number;
    use(): void;
}

@injectable()
class Sword implements Weapon {
    public name: string;
    public durability: number;
    public constructor() {
        this.durability = 100;
        this.name = "Sword";
    }
    public use() {
        this.durability = this.durability - 10;
    }
}

@injectable()
class Shuriken implements Weapon {
    public name: string;
    public durability: number;
    public constructor() {
        this.durability = 100;
        this.name = "Shuriken";
    }
    public use() {
        this.durability = this.durability - 10;
    }
}

class Warrior {

    @lazyInjectNamed(TYPES.Weapon, "not-throwable")
    @named("not-throwable")
    public primaryWeapon: Weapon;

    @lazyInjectNamed(TYPES.Weapon, "throwable")
    @named("throwable")
    public secondaryWeapon: Weapon;

}

container.bind<Weapon>(TYPES.Weapon).to(Sword).whenTargetNamed("not-throwable");
container.bind<Weapon>(TYPES.Weapon).to(Shuriken).whenTargetNamed("throwable");

let warrior = new Warrior();
console.log(warrior.primaryWeapon instanceof Sword); // true
console.log(warrior.primaryWeapon instanceof Shuriken); // true

Tagged property injection with @lazyInjectTagged

The following example showcases how to inject a tagged property using the @lazyInjectTagged decorator:

import getDecorators from "inversify-inject-decorators";
import { Container, injectable, tagged } from "inversify";

let container = new Container();
let { lazyInjectTagged } = getDecorators(container);
let TYPES = { Weapon: "Weapon" };

interface Weapon {
    name: string;
    durability: number;
    use(): void;
}

@injectable()
class Sword implements Weapon {
    public name: string;
    public durability: number;
    public constructor() {
        this.durability = 100;
        this.name = "Sword";
    }
    public use() {
        this.durability = this.durability - 10;
    }
}

@injectable()
class Shuriken implements Weapon {
    public name: string;
    public durability: number;
    public constructor() {
        this.durability = 100;
        this.name = "Shuriken";
    }
    public use() {
        this.durability = this.durability - 10;
    }
}

class Warrior {

    @lazyInjectTagged(TYPES.Weapon, "throwable", false)
    @tagged("throwwable", false)
    public primaryWeapon: Weapon;

    @lazyInjectTagged(TYPES.Weapon, "throwable", true)
    @tagged("throwwable", true)
    public secondaryWeapon: Weapon;

}

container.bind<Weapon>(TYPES.Weapon).to(Sword).whenTargetTagged("throwable", false);
container.bind<Weapon>(TYPES.Weapon).to(Shuriken).whenTargetTagged("throwable", true);

let warrior = new Warrior();
console.log(warrior.primaryWeapon instanceof Sword); // true
console.log(warrior.primaryWeapon instanceof Shuriken); // true

Multi-injection into a property with @lazyMultiInject

The following example showcases how to multi-inject a property using the @lazyMultiInject decorator:

import getDecorators from "inversify-inject-decorators";
import { Container, injectable } from "inversify";

let container = new Container();
let { lazyMultiInject } = getDecorators(container);
let TYPES = { Weapon: "Weapon" };

interface Weapon {
    name: string;
    durability: number;
    use(): void;
}

@injectable()
class Sword implements Weapon {
    public name: string;
    public durability: number;
    public constructor() {
        this.durability = 100;
        this.name = "Sword";
    }
    public use() {
        this.durability = this.durability - 10;
    }
}

@injectable()
class Shuriken implements Weapon {
    public name: string;
    public durability: number;
    public constructor() {
        this.durability = 100;
        this.name = "Shuriken";
    }
    public use() {
        this.durability = this.durability - 10;
    }
}

class Warrior {

    @lazyMultiInject(TYPES.Weapon)
    public weapons: Weapon[];

}

container.bind<Weapon>(TYPES.Weapon).to(Sword);
container.bind<Weapon>(TYPES.Weapon).to(Shuriken);

let warrior = new Warrior();
console.log(warrior.weapons[0] instanceof Sword); // true
console.log(warrior.weapons[1] instanceof Shuriken); // true