@karcass/container

Very tiny and simple async IoC container with dependency injection support used in karcass skeleton

Installation

npm install @karcass/container

Usage

import { Container } from '@karcass/container'

class ConsoleLogger {
    public log(text: string) {
        console.log(text)
    }
}

class HelloMessagePrinter {
    public constructor(protected helloSayer: HelloSayer) {}

    public print(username: string) {
        this.helloSayer.log(`Hello, ${username}!`)
    }
}

class DummyClass {}

const container = new Container()

container.add(HelloWorldMessagePrinter, async () => {
    const logger = await container.get(ConsoleLogger)
    console.log('HelloMessagePrinter initialization...')
    return new HelloMessagePrinter(logger)
})
container.add(ConsoleLogger, () => {
    console.log('ConsoleLogger initialization...')
    return new ConsoleLogger()
}
container.add(DummyClass, () => {
    console.log('DummyClass initialization...')
    return new DummyClass()
})

container.get(HelloMessagePrinter).then(printer => printer.print('Alice'))

This example will print:

ConsoleLogger initialization...
HelloMessagePrinter initialization...
Hello, Alice!

Also you can use addInplace method for immediate initialization of some instances for some reasons:

container.add(HelloWorldMessagePrinter, () => {
    const logger = container.get(ConsoleLogger)
    console.log('HelloMessagePrinter initialization...')
    return new HelloMessagePrinter(logger)
})
container.add(ConsoleLogger, () => {
    console.log('ConsoleLogger initialization...')
    return new ConsoleLogger()
}
container.addInplace(DummyClass, () => {
    console.log('DummyClass initialization... It was first.')
})

container.get(HelloMessagePrinter).print('Alice')

Ouput:

DummyClass initialization... It was first.
ConsoleLogger initialization...
HelloMessagePrinter initialization...
Hello, Alice!

You can use dependency injection instead of service construction by hands:

import { Container, Dependency } from '@karcass/container'

class FirstClass {}

class SecondClass {
    public constructor(@Dependency(FirstClass) firstClassInstance: FirstClass) {
        console.log(`${firstClassInstance.constructor.name} loaded`)
    }
}

const container = new Container()
container.add(FirstClass)
await container.addInplace(SecondClass)

Or you can just create instance of SecondClass using inject method, which creates instance of constructor and injects corresponding dependencies. This method doesn't perform addition of created object into self (container's) index:

const secondClassInstance = await container.inject(SecondClass)

Feel free to use text keys for services:

/* ... */
public constructor(@Dependency('first-class') firstClassInstance: FirstClass) {
/* ... */
container.add('first-class', () => new FirstClass())
await container.addInplace(SecondClass)

Available methods

• add<T>(key: costructor | string, initializer?: () => T | Promise<T>): void;
• addInplace<T>(key: consructor | string, initializer?: () => T | Promise<T>): Promise<T>;
• get<T>(key: constructor | string): Promise<T>;
• getAll(): Promise<T[]>;
• getKeys(): (string | constructor)[].