Created
October 18, 2022 16:29
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A very naive solution for Dependency Injection
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function createAppContainer() { | |
const bindingsMap = new Map(); | |
const appContainer = { | |
bind(abstractClass, concreteClassOrFn) { | |
bindingsMap.set(abstractClass, concreteClassOrFn); | |
}, | |
make(ClassToCreate, ...constructorArgs) { | |
const argTypes = ClassToCreate.argTypes || []; | |
// For now naively just use the args and don't inject | |
if (constructorArgs.length > 0) { | |
return new ClassToCreate(...constructorArgs); | |
} else { | |
const injectedArgs = argTypes.map((ArgClass) => { | |
const ClassToInjectOrFn = bindingsMap.get(ArgClass); | |
if (ClassToInjectOrFn) { | |
return Object.getPrototypeOf(ClassToInjectOrFn) === ArgClass | |
? make(ClassToInjectOrFn) | |
: ClassToInjectOrFn(appContainer); | |
} else { | |
if (ArgClass.argTypes) { | |
return make(ArgClass); | |
} else { | |
return new ArgClass(); | |
} | |
} | |
}); | |
return new ClassToCreate(...injectedArgs); | |
} | |
}, | |
}; | |
return appContainer; | |
} | |
const { bind, make } = createAppContainer(); | |
class Bar { | |
getName() { | |
throw new Error('Bar should be implemented'); | |
} | |
} | |
class CoolBar extends Bar { | |
getName() { | |
return 'really cool bar'; | |
} | |
} | |
class Foo { | |
static get argTypes() { | |
return [Bar]; | |
} | |
constructor(bar) { | |
this.bar = bar; | |
} | |
getBar() { | |
return this.bar; | |
} | |
} | |
class NiceFoo extends Foo { | |
getName() { | |
return 'nice foo'; | |
} | |
} | |
class Pet { | |
constructor(name) { | |
this.name = name; | |
} | |
getName() { | |
return this.name; | |
} | |
} | |
class Cat extends Pet { | |
constructor() { | |
super('cat') | |
} | |
} | |
class Consumer { | |
constructor(foo, pet) { | |
this.foo = foo; | |
this.pet = pet; | |
} | |
showFooNameAndBarName() { | |
console.log(this.foo.getName()); | |
console.log(this.foo.getBar().getName()); | |
} | |
showPetName() { | |
console.log(this.pet.getName()) | |
} | |
} | |
Consumer.argTypes = [Foo, Pet] | |
bind(Foo, NiceFoo); | |
bind(Bar, CoolBar); | |
bind(Pet, (appContainer) => appContainer.make(Cat)); | |
const consumer = make(Consumer); | |
console.log(consumer.showFooNameAndBarName()); | |
console.log(consumer.showPetName()); |
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