@thaitype/ioctopus
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A simple IoC container for JavaScript and TypeScript for classes and functions.
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# A simple IOC container for Typescript
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[](https://codecov.io/gh/Evyweb/ioctopus)
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## Introduction
An IOC (Inversion of Control) container for Typescript.
The idea behind is to create a simple container that can be used to register and resolve dependencies working with classes & functions but without reflect metadata.
It is using simple Typescript code, so it can be used in any project without any dependency.
Works also in NextJS middleware and node+edge runtimes.
## Installation
```npm i @thaitype/ioctopus```
## How to use
To use the container, you need to create a container and bind your dependencies.
To do so you need to create an id for each dependency you want to register.
This id that we call an "injection token" can be a string or a symbol.
(Please note that you have to be consistent and use always strings for binding and resolving dependencies or always symbols, you can't mix them).
Then you can bind the dependency to a value, a function, a class, a factory, a higher order function, or a curried function.
### Using symbols as injection tokens
a) create a service registry file (`ServiceRegistry.ts`) where you will define your symbols
```typescript
import { createServiceRegistry } from '@thaitype/ioctopus';
export const serviceRegistry = createServiceRegistry()
.define('DEP1').mapTo<string>()
.define('DEP2').mapTo<number>()
.define('LOGGER').mapTo<LoggerInterface>()
.define('MY_SERVICE').mapTo<MyServiceInterface>()
.define('MY_USE_CASE').mapTo<MyUseCaseInterface>()
.define('SIMPLE_FUNCTION').mapTo<SayHelloType>()
.define('CLASS_WITH_DEPENDENCIES').mapTo()
.define('CLASS_WITHOUT_DEPENDENCIES').mapTo()
.define('HIGHER_ORDER_FUNCTION_WITH_DEPENDENCIES').mapTo<MyServiceInterface>()
.define('HIGHER_ORDER_FUNCTION_WITHOUT_DEPENDENCIES').mapTo<ServiceWithoutDependencyInterface>()
```
b) Then create your container.
```typescript
import { serviceRegistry } from './ServiceRegistry';
const container: Container = createContainer(serviceRegistry);
```
### Register the dependencies
#### Primitives
You can register primitives
> this might use bind with string, but internally it will be converted to a symbol by the service registry
```typescript
container.bind('DEP1').toValue('dependency1');
container.bind('DEP2').toValue(42);
```
#### Functions
- You can register functions without dependencies
```typescript
const sayHelloWorld = () => console.log('Hello World');
container.bind('SIMPLE_FUNCTION').toFunction(sayHelloWorld);
```
#### Currying
- You can register functions with dependencies using currying (1 level of currying)
```typescript
const myFunction = (dep1: string, dep2: number) => (name: string) => console.log(`${dep1} ${dep2} ${name}`);
container.bind('CURRIED_FUNCTION_WITH_DEPENDENCIES')
.toCurry(myFunction, ['DEP1', 'DEP2']);
```
- You can also use a dependency object
```typescript
interface Dependencies {
dep1: string,
dep2: number
}
const myFunction = (dependencies: Dependencies) => (name: string) => console.log(`${dependencies.dep1} ${dependencies.dep2} ${name}`);
// The dependencies will be listed in an object in the second parameter
container.bind('CURRIED_FUNCTION_WITH_DEPENDENCIES')
.toCurry(myFunction, {dep1: 'DEP1', dep2: 'DEP2'});
```
#### Higher order functions
You can also register functions with dependencies by using higher order functions
```typescript
const MyServiceWithDependencies = (dep1: string, dep2: number): MyServiceWithDependenciesInterface => {
return {
runTask: () => {
// Do something with dep1 and dep2
}
};
};
// The dependencies will be listed in an array in the second parameter
container.bind('HIGHER_ORDER_FUNCTION_WITH_DEPENDENCIES')
.toHigherOrderFunction(MyServiceWithDependencies, ['DEP1', 'DEP2']);
```
But if you prefer, you can also use a dependency object
```typescript
interface Dependencies {
dep1: string,
dep2: number
}
const MyService = (dependencies: Dependencies): MyServiceInterface => {
return {
runTask: () => {
// Do something with dependencies.dep1 and dependencies.dep2
}
};
};
// The dependencies will be listed in an object in the second parameter
container.bind('HIGHER_ORDER_FUNCTION_WITH_DEPENDENCIES')
.toHigherOrderFunction(MyService, {dep1: 'DEP1', dep2: 'DEP2'});
```
#### Factories
For more complex cases, you can register factories.
```typescript
container.bind('MY_USE_CASE').toFactory(() => {
// Do something before creating the instance
// Then return the instance
return MyUseCase({
myService: container.get('MY_SERVICE')
});
});
```
#### Classes
You can register classes, the dependencies of the class will be resolved and injected in the constructor
```typescript
class MyServiceClass implements MyServiceClassInterface {
constructor(
private readonly dep1: string,
private readonly dep2: number,
) {}
runTask(): string {
return `Executing with dep1: ${this.dep1} and dep2: ${this.dep2}`;
}
}
container.bind('CLASS_WITH_DEPENDENCIES').toClass(MyServiceClass, ['DEP1', 'DEP2']);
```
But if you prefer, you can also use a dependency object:
```typescript
interface Dependencies {
dep1: string,
dep2: number
}
class MyServiceClass implements MyServiceClassInterface {
constructor(private readonly dependencies: Dependencies) {}
runTask(): string {
return `Executing with dep1: ${this.dependencies.dep1} and dep2: ${this.dependencies.dep2}`;
}
}
container.bind('CLASS_WITH_DEPENDENCIES').toClass(MyServiceClass, {dep1: 'DEP1', dep2: 'DEP2'});
```
- You can register classes without dependencies:
```typescript
class MyServiceClassWithoutDependencies implements MyServiceClassInterface {
runTask(): string {
return `Executing without dependencies`;
}
}
container.bind('CLASS_WITHOUT_DEPENDENCIES').toClass(MyServiceClassWithoutDependencies);
```
### Resolve the dependencies
You can now resolve the dependencies using the get method of the container.
```typescript
// Primitive
const dep1 = container.get('DEP1'); // 'dependency1'
const dep2 = container.get('DEP2'); // 42
// Higher order function and class
const myUseCase = container.get('MY_USE_CASE'); // `myUseCase` will be instance of `MyUseCaseInterface` automatically
myUseCase.execute();
// Simple function
const simpleFunction = container.get('SIMPLE_FUNCTION'); // `simpleFunction` will be a function type for `SimpleFunctionType` automatically
simpleFunction('Hello World');
// Curried function
const callMe = container.get('CURRIED_FUNCTION_WITH_DEPENDENCIES'); // type will be `CurriedFunction`
callMe('John Doe');
```
### Modules
You can also use modules to organize your dependencies.
#### Loading modules
Modules can then be loaded in your container.
By default, when you create a container, it is using a default module under the hood.
```typescript
const module1 = createModule(serviceRegistry);
module1.bind('DEP1').toValue('dependency1');
const module2 = createModule(serviceRegistry);
module2.bind('DEP2').toValue(42);
const module3 = createModule(serviceRegistry);
module3.bind('MY_SERVICE').toHigherOrderFunction(MyService, {dep1: 'DEP1', dep2: 'DEP2'});
const container = createContainer();
container.load(Symbol('module1'), module1);
container.load(Symbol('module2'), module2);
container.load(Symbol('module3'), module3);
const myService = container.get('MY_SERVICE');
```
The dependencies do not need to be registered in the same module as the one that is using them.
Note that the module name used as a key can be a symbol or a string.
#### Modules override
You can also override dependencies of a module. The dependencies of the module will be overridden by the dependencies of the last loaded module.
```typescript
const module1 = createModule(serviceRegistry);
module1.bind('DEP1').toValue('OLD dependency1');
module1.bind('MY_SERVICE').toFunction(sayHelloWorld);
const module2 = createModule(serviceRegistry);
module2.bind('DEP1').toValue('NEW dependency1');
const module3 = createModule(serviceRegistry);
module3.bind('MY_SERVICE').toHigherOrderFunction(MyService, {dep1: 'DEP1', dep2: 'DEP2'});
const container = createContainer();
container.bind('DEP2').toValue(42); // Default module
container.load(Symbol('module1'), module1);
container.load(Symbol('module2'), module2);
container.load(Symbol('module3'), module3);
// The dependency "MY_SERVICE" will be resolved with the higher order function and dep1 will be 'NEW dependency1'
const myService = container.get('MY_SERVICE');
```
#### Unload modules
You can also unload a module from the container. The dependencies of the module will be removed from the container.
Already cached instances will be removed to keep consistency and avoid potential errors.
```typescript
const module1 = createModule(serviceRegistry);
module1.bind('DEP1').toValue('dependency1');
const container = createContainer(serviceRegistry);
container.load(Symbol('module1'), module1);
container.unload(Symbol('module1'));
// Will throw an error as the dependency is not registered anymore
const myService = container.get('DEP1');
```
### Using scopes
#### Singleton scope (default)
In singleton scope, the container returns the same instance every time a dependency is resolved.
```typescript
container.bind('MY_SERVICE').toClass(MyServiceClass, ['DEP1', 'DEP2']);
// or
container.bind('MY_SERVICE').toClass(MyServiceClass, ['DEP1', 'DEP2'], 'singleton');
const instance1 = container.get('MY_SERVICE');
const instance2 = container.get('MY_SERVICE');
console.log(instance1 === instance2); // true
```
#### Transient scope
In transient scope, the container returns a new instance every time the dependency is resolved.
```typescript
container.bind('MY_SERVICE').toClass(MyServiceClass, ['DEP1', 'DEP2'], 'transient');
const instance1 = container.get('MY_SERVICE');
const instance2 = container.get('MY_SERVICE');
console.log(instance1 === instance2); // false
```
#### Scoped Scope
In scoped scope, the container returns the same instance within a scope. Different scopes will have different instances.
To use the scoped scope, you need to create a scope using runInScope.
```typescript
container.bind('MY_SERVICE').toClass(MyServiceClass, ['DEP1', 'DEP2'], 'scoped');
const instance1 = undefined;
const instance2 = undefined;
container.runInScope(() => {
instance1 = container.get("MY_SERVICE");
instance2 = container.get("MY_SERVICE");
console.log(instance1 === instance2); // true
});
container.runInScope(() => {
const instance3 = container.get("MY_SERVICE");
console.log(instance3 === instance1); // false
});
```
Note: If you try to resolve a scoped dependency outside a scope, an error will be thrown.
### Circular dependencies
IOctopus can detect circular dependencies.
An error will be thrown if a circular dependency is detected.
```typescript
const container = createContainer(serviceRegistry);
const A_TOKEN = Symbol('A');
const B_TOKEN = Symbol('B');
class A {
constructor(public b: B) {}
}
class B {
constructor(public a: A) {}
}
container.bind('A').toClass(A, ['B']);
container.bind('B').toClass(B, ['A']);
container.get('A'); // Will throw: "Circular dependency detected: Symbol(A) -> Symbol(B) -> Symbol(A)"
```
This way you can avoid infinite loops and stack overflow errors.