Highly inspired by Autofac.NET
We have tried to accommodate all the best DI and IoC practices for JavaScript
const di = new Di;
-
2.1Constructor2.1.1External definitions2.1.2Decorators2.1.3Default parameters2.1.4In-place meta information2.1.5Other ways
2.2Properties2.3Methods
-
3Consume
The greatest challenge for DI frameworks in JavaScript is to get the list of dependencies for a constructor, method, etc. JavaScript is not statically typed, so here other ways should be found to declare the dependencies. And we also try to follow the 1st rule of any di framework -
"Your classes should not be dependent on the DI itself".
Though you can use it as a Service Locator
When registering the component, you specify identifiers, by which the dependency is resolved. It can be some another Type, string identifier. But we do not encourage you to use string identifiers.
It is also possible to get the instance without having previously to register the Type
const foo = di.resolve(Foo);Later you can register another Type for this one.
Class constructor;
class Foo {
constructor (bar, qux) {}
}Pass already instantiated class to the container, and it will be used by all dependents
di.registerInstance(new Foo(di.resolve(IBar), di.resolve(IQux))).as(IFoo);
// or use Initializer wich will be called on first `IFoo` require.
di.registerInstance(IBar, IFoo, (bar, foo) => new Foo(bar, foo)).as(IFoo);
// you can even suppress the lamda here
di.registerInstance(IBar, IFoo, Foo).as(IFoo);Register a function which will create the instance on demand. Is similar to instance initializer, but the factory is called every time the dependency is required.
di.registerFactory(IBar, (bar) => {}).as(IFoo);
// No arguments are defined - we pass the di itself, for the case your factory method is out of the current di scope.
di.registerFactory(di => {}).as(IFoo);From the previous paragraph you have already seen using method, when registering the Type. Here we define what identifiers should be used to instantiate the instance.
✨ Pros: Your implementation is fully decoupled from the DI and the registration itself.
class Foo {
constructor (logger) { logger.log() }
}
// ----
class Bar {
log (...args) { console.log(...args) }
}
// ---
class ILog { log () {} }
// ---
di
.registerType(Bar)
.as(ILog);
di
.registerType(Foo)
.using(ILog)
.asSelf()
.onActivated(foo => console.log(foo));✨ Pros: In-place configuration, but has reference to the di instance
class Foo {
constructor (@di.inject(ILog) logger) {
logger.log()
}
}✨ Pros:
new Foo()also works
class Foo {
constructor (logger = di.resolve(ILog)) {
logger.log()
}
}Maybe most irrelevant feature, but anyway
✨ Pros: Your implementation is decoupled from the DI, but holds meta information for the DI library.
Per default we read the static $inject property on the Type
class Foo {
static $constructor = [ ILog ]
constructor (logger) { logger.log() }
}You can override the reader and provide us with the Identifiers for injection.
const CustomMetaReader = {
getConstructor (Type) {
return Type.$inject;
}
};
di.defineMetaReader(CustomMetaReader);
// ----
class Foo {
static $inject = [ILog]
constructor (logger) { logger.log() }
}💬 Do you have any ideas? Please share them via issues.
TypeScript: initially, this project targets plain JavaScript, but TypeScript is preferred.
Property injections are supported by Types components.
class Foo {
constructor () {
this.logger = new DummyLogger();
}
doSmth () {
this.logger.log();
}
}
// ---
di
.registerType(Foo)
.properties({
// DummyLogger will be replaced with the registration for ILog
logger: ILog
})
.asSelf();Per default we read the static $properties to get the key: Identifier information.
class Foo {
constructor () { }
}
Foo.$properties = {
logger: ILog
};
// ----
di
.registerType(Foo)
.asSelf();You can override the reader and provide us with the Identifiers for injection.
let CustomMetaReader = {
getProperties (Type) {
// return hash with {key: Identifier}
}
};
di.defineMetaReader(CustomMetaReader);💬 Ideas about better API - please share!
Injections into Type_s_functions.
class Foo {
doSmth (logger) {
logger.log();
}
}
// ---
di
.registerType(Foo)
.methods({
// The method on an instance can be the called without any arguments
// Di will provide required dependencies to the inner function
doSmth: [ILog]
})
.asSelf();Per default we read the static $methods with key:[Identifier, ...] information.
class Foo {
doSmth (logger) { logger.log() }
static $methods = {
doSmth: [ ILog ]
};
}
// ----
di
.registerType(Foo)
.asSelf();You can override the reader and provide us with the Identifiers for injection.
const CustomMetaReader = {
getMethods (Type) {
// return hash with {key: [Identifier, ...]}
}
};
di.defineMetaReader(CustomMetaReader);💬 Ideas about better API - please share!
We inject all dependencies and return ready to use component.
let x = di.resolve(IFoo);The inherited class accepts empty constructor, in this case we will pass the resolved components to the base class.
let FooWrapper = di.wrapType(IFoo);
let foo = new FooWrapper();Define function argument identifiers, and you can call the function without arguments.
let myFunction = di.wrapFunction(IFoo, IBar, (foo, bar) => {});
myFunction();Sometimes it is needed to set values for parameters, which will be directly passed inside the function.
class Foo {
constructor (bar, shouldDoSmth)
}
di
.registerType(Foo)
.using(Bar)
.withParams(null, true)1️⃣ Passing null values says the di library to resolve values from container by declared Type
2️⃣ Boolean
truefrom sample just shows the idea of passing values. You may want to get the value from app configuration or some other source.
Arguments or values for a constructor/function are resolved from 3 sources:
- Declared parameter values
- Type definitions
- Direct values from the current function call.
With options "ignore" "extend" "override" you can control how we handle the third source. Default is "override"
We rarely use all of those registration and configuration features.
- All the
Services,Workers,Handlers,Factories- actually everything exceptData Models- we use mostly as singletons. Means any initialization of an Instance we do viadi.resolve. Note, that no configuration or registration is required - when nothing specified di initializes the class as-is.
We do this, while a class can
memoizeinitialization, data, configuration, or method calls.
import { UserService } from './UserService'
// ....
let service = di.resolve(UserService);- To have more clear dependency tree structure, we define some dependencies via constructor as default parameters:
import { UserService } from './UserService'
// ....
class Foo {
constructor (
private service = di.resolve(UserService)
)
}- For multiple implementations we use abstract classes.
abstract class AFoo {
abstract log ()
// ... some common logic
}
// Option 1. Register the implementation as a default for the base (AFoo)
@di.for(AFoo)
class SomeFoo extends AFoo () {}
// Option 2. Without the decorator, the type could be registered later somewhere in code:
di.registerType(AFoo).for(AFoo)
//# Usage 1
class UserService {
constructor (
foo = di.resolve(AFoo)
) {}
}
//# Usage 2
class UserService {
constructor (
@di.inject(AFoo) foo: AFoo
){}
}🏁
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