Capsule

Lightweight TypeScript service container.

Note: This is just quick preview of the documentation, not even alpha quality. For more detailed stuff, please check the tests as they contain more examples.

Installation

Deno

Capsule is built and tested for Deno. You can install it simply by importing:

import { container } from 'https://deno.land/x/capsule_sc/mod.ts';

Usage

The idea behind Capsule is to have super declarative and explicit service container. Thanks to this approach we managed to create Capsule without any reflection libraries.

class UserRepository {
  username() {
    return "@capsule";
  }
}

class UserService {
  constructor(
    @Inject(UserRepository) public repo: UserRepository,
  ) {}
}

Now we can construct the UserService using get.

container.get<UserService>(UserService).repo.username();

// "@capsule"

Binding to interfaces

In TypeScript interfaces are wiped during the compilation, so we can't use them as a values. As replacement, Capsule lets you bind using symbols. This is quite effective replacement for binds to interface. Let's see how it works.

The first part is as you would expect. Having a class that implements a interface.

interface Repository {
  username(): string;
}

class UserRepository implements Repository {
  username() {
    return "@capsule";
  }
}

Now, as identifier we use Symbol.

const repositoryInterface = Symbol();

Let's bind a property and as identifier use repositoryInterface.

container.set(repository, UserService, () => new UserRepository(), {
  position: 0,
  property: "constructor",
});

... and instead of @Inject we make use of @InjectSymbol:

class UserService {
  constructor(
    @InjectSymbol(repository) public repo: Repository
  ) {}
}

Notice how type is interface, not specific class.

container.get<UserService>(UserService).repo.username();

// "@capsule"

Licence

The MIT License (MIT). Please see licence file for more information.