simpledi-node

SimpleDi

This is a fork and complete rewrite of SimpleDi, a very simple dependency injector.

Intended for Node 10+ environments.

Features

• Simple API
• No dependencies
• Fully tested
• Helps you find unresolved dependencies with getResolvedDependencyCount

Installation

npm install simpledi-node

API

Create a SimpleDi instance

const SimpleDi = require('simpledi-node');
const di = new SimpleDi(); 

Add dependency with factory function

di.registerWithFactory(name, factoryFn, dependencies, overwrite)

di.registerWithFactoryOnce(name, factoryFn, dependencies, overwrite)

Parameter	Type	Description
name	string	The name of the dependency
factoryFn	function	A function that gets called when di.get(name) is called
dependencies	string[]	optional array of dependency names. The dependencies will be resolved and passed to the factoryFn when di.get(name) is called.
overwrite	boolean	optional This allows to explicitly overwrite dependencies

Add dependency with class constructor

di.registerWithNew(name, clazz, dependencies, overwrite)

di.registerWithNewOnce(name, clazz, dependencies, overwrite)

Parameter	Type	Description
name	string	The name of the dependency
clazz	function	A class or constructor function that gets instantiated when di.get(name) is called
dependencies	string[]	optional array of dependency names. The dependencies will be resolved and passed to the constructor when di.get(name) is called.
overwrite	boolean	optional This allows to explicitly overwrite dependencies

Example

const SimpleDi = require('simpledi-node');
const di = new SimpleDi();

function Engine(config) {
    this.hp = config.hp;
    this.maxSpeed = config.maxSpeed;
}

function Car(engine) {
    this.text = 'This car has ' + engine.hp + 'hp!';
}

di.registerWithNew('Engine', Engine, ['engineConfig']);
di.registerConstant('engineConfig', {
    hp: 120,
    maxSpeed: 200
});
di.registerWithNewOnce('Car', Car, ['Engine']);

let car = di.get('Car'); 

console.log(car.text); // This car has 120hp!

Add constant dependency

di.registerConstant(name, value, overwrite)

Parameter	Type	Description
name	string	The name of the dependency
value	mixed	A fix value to be returned whenever di.get(name) is called
overwrite	boolean	optional This allows to explicitly overwrite dependencies

di.registerContants(keyValueMap, keyPrefix, overwrite)

Parameter	Type	Description
keyValueMap	Map<string,*> or Object	An map or pojo whose (own) keys will be used to register the respective value as a constant
prefix	string	optional prefix to precede the registered keys
overwrite	boolean	optional This allows to explicitly overwrite dependencies

Example:

const CC = {foo: 1, bar: 2};
di.registerConstants(CC);
di.get('foo'); // returns 1
di.registerConstants(CC, 'tmp.');
di.get('tmp.bar'); // returns 2

Get a dependency

di.get(name[, arg1[, arg2[, ...]]])

Returns a previously registered dependency and resolves all dependencies.
Throws an Error if the dependency is not registered.

Name	Type	Description
name	string	The name of the dependency
arg1, arg2, ...	mixed	optional arguments that will be passed to the dependency's factory function or constructor additionally to its dependencies

Example:

const fn = function() { return [...arguments] };
di.registerWithFactory('foo', fn, ['BAR']);
di.registerConstant('BAR', 111);
di.get('foo', 444, 555); // returns [111, 444, 555]

NOTE: For dependencies registered via registerWithNewOnce() or registerWithFactoryOnce(), additional get-arguments (arg1, arg2, ...) are allowed only in the first invocation of di.get(). An error is thrown otherwise.
You can suppress this error by calling di.setIgnoreArgsPassedToFinalValue(true).

Example for circular dependency (throws error):

di.registerWithNew('A', class{}, ['B']);
di.registerWithNew('B', class{}, ['C']);
di.registerWithNew('C', class{}, ['A']);

di.get('A'); // throws "Circular Dependency detected: A => B => C => A"

Inspecting usages of dependencies

di.getResolvedDependencyCount(): Map<string, number>

Returns a Map of dependency names onto the number the dependency got resolved in total, including both direct di.get() calls and transitive resolving.

// Example
console.warn(...di.getResolvedDependencyCount()); // [ 'foo', 3 ] [ 'bar', 1 ]

License

MIT