Terso

dependency injection hooks for React.

Terso is a pragmatic hook and HOC library for React, that provides dependency injection to a React application. It uses inversify js as an IoC container, in combination with mobx for state management.

Is it a revolutionary library? No! It is just a collection of functions, born with the sole need of not wanting to copy/paste the same code into different projects.

• Terso
  • Quick start
    • 1. Install
    • 1.1 Configure typescript
    • 1.2 Copy/paste qwickstart
    • 2. Wrap your App in the terso IoC Context
    • 3. Use a dependency in React Components
  • Hooks
    • useInject
    • useModel

Quick start

Quick start in three easy steps

1. Install

npm install terso
# yarn add terso

1.1 Configure typescript

Add these entries in the compilerOptions of your typescript config

"experimentalDecorators": true,
"types": ["reflect-metadata"],

1.2 Copy/paste qwickstart

interface TestModel extends ViewModel {
  value: string;
}

const value = "the value";

@injectable()
class TestPresenter implements Presenter<TestModel> {
  loadViewModel(): Promise<void> {
    return Promise.resolve();
  }
  cleanModel(): Promise<void> {
    return Promise.resolve();
  }

  get viewModel() {
    return {
      value: value,
    };
  }
}

function App() {
  const model = useModel<TestModel>(TestPresenter);
  return <div>{model.value}</div>;
}

function setup(container: Container) {
  container
    .bind<TestPresenter>(TestPresenter)
    .to(TestPresenter)
    .inSingletonScope();
}

const WithIoc = withIoc(App, setup);

const root = ReactDOM.createRoot(
  document.getElementById('root')
);
root.render(<WithIoc />);

2. Wrap your App in the terso IoC Context

// App.tsx

import { withIoc } from "terso";
import { Container } from "inversify";
import { configureContainer } from "./ioc/ioc.config";

function App() {
  return <main>My app</main>
}

export default withIoc(App, configureContainer);


// ioc/ioc.types.ts
export const TYPES = {
  TodoStore: Symbol.for("TodoStore"),
  TodoBaseUrl: Symbol.for("TodoBaseUrl"),
};

// oic.config.js
import "reflect-metadata"
import {TYPES} from "./ioc.types";
//import {TodoStore } from "../stores/TodoStore"
//import {TodoStoreImpl } from "../stores/impl/TodoStoreImpl"

export function configureContainer(container: Container) {
  
  // define here the dependencies of your code: services, api, repositories, configurattions
  // for example: 
  container.bind<string>(TYPES.TodoBaseUrl).toConstantValue(/*config.todoBaseUrl*/ "some url");
  // container
  //   .bind<TodoStore>(TYPES.TodoStore)
  //   .to(TodoStoreImpl)
  //   .inSingletonScope();

}

The function configureContainer is mandatory and takes the IoC container as an argument. You can add (bind) alle the dependency you need in the app into the container.

3. Use a dependency in React Components

import { useInject } from "terso";
import { observer } from "mobx-react-lite";
import { TYPES } from "../ioc/ioc.types";
import { TodoStore } from "../stores/TodoStore";

export default observer(function Todolist() {
  const todoStore = useInject<TodoStore>(TYPES.TodoStore);
  return (
    <main>
      <h2>Todo list</h2>
      {todoStore.todos
        .slice()
        .map((todo) => (
          <Todo key={todo.id} todo={todo} />
        ))}
    </main>
  );
})

Hooks

terso provides these hooks:

• useInject
• useModel

useInject

The hook useInject takes an object from the IoC container and returns it, ready to be used in a React component.

Signature

useInject<T>(type: ServiceIdentifier<T>): T

Usage

const myService = useInject<MyServiceType>(MyServiceIdentifier);

Example

import { useInject } from "terso";
import { observer } from "mobx-react-lite";
import { TYPES } from "../ioc/ioc.types";
import { TodoStore } from "../stores/TodoStore";

export default observer(function Todolist() {
  const todoStore = useInject<TodoStore>(TYPES.TodoStore);

  return (
    <main>
      <h2>Todo list</h2>
      {todoStore.todos
        .slice()
        .map((todo) => (
          <Todo key={todo.id} todo={todo} />
        ))}
    </main>
  );
})

useModel

useModel provides a ViewModel implementation in a React Component.

A ViewModel is an interface, borrowed from the famous pattern Model-View-Presenter. To use it you have to create an implementation of the ViewModel interface and an implementation of a Presenter that are defined as follows:

export interface ViewModel {
  [key: string]: any;
}

export interface Presenter {
  loadViewModel(): Promise<void>;
  cleanModel(): Promise<void>;
  viewModel: ViewModel;
}

The Presenter interface provides a method to load the ViewModel, a method to clean, and the ViewModel itself.

Presenters are useful for leaving React components simple by giving them a flat object to display: the ViewModel. The presenter hides the business logic from the React component, so finally React components can be used for what they were designed: creating user interfaces.

Signature

export function useModel<T extends ViewModel>(type: ServiceIdentifier<Presenter>): T 

Usage

const viewModel = useModel<MyViewModelType>(MyPresenterIdentifier);

Example

// Todo.tsx
import { observer } from "mobx-react-lite";
import { Todo as TodoType } from "../../../domain/Todo";
import { useModel } from "terso";
import { TodoPresenter, TodoViewModel } from "../../../presenter/TodoPresenter";

interface TodoProps {
  todo: TodoType;
}

export default observer(function Todo({ todo }: TodoProps) {
  const viewModel = useModel<TodoViewModel>(TodoPresenter);

  return (
    <li className="todo-card">
      <span className={todo.completed ? "done" : "todo"}>
        {todo.id} - {todo.title}
      </span>
      {viewModel.canDelete && <button>delete</button>}
    </li>
  );
})


// TodoPresenter.ts
import { inject, injectable } from "inversify";
import { action, makeObservable, observable } from "mobx";
import { TYPES } from "../ioc/ioc.types";
import {
  Permissions,
  type AuthorizationService,
} from "../service/AuthorizationService";
import { type TodoStore } from "../service/TodoService";
import { Presenter, ViewModel } from "terso";

export interface TodoViewModel extends ViewModel {
  canDelete: boolean;
}

@injectable()
export class TodoPresenter implements Presenter {
  @inject(TYPES.TodoStore)
  private readonly todoService!: TodoStore;

  @inject(TYPES.AuthorizationServiceType)
  private readonly authService!: AuthorizationService;

  private canDelete: boolean = false;

  constructor() {
    makeObservable<TodoPresenter, "canDelete">(this, {
      canDelete: observable,
      loadViewModel: action,
    });
  }
  loadViewModel(): Promise<void> {
    this.canDelete = this.authService.hasPermission(Permissions.todo.delete);
    return Promise.resolve();
  }
  cleanModel(): Promise<void> {
    return Promise.resolve();
  }

  get viewModel(): TodoViewModel {
    return {
      canDelete: this.canDelete,
    };
  }
}