cqrs-with-es v1.0.0

cqrs-with-es

cqrs-with-es is a library that will help you easily set up a CQRS/event sourcing system

typescript support

cqrs-with-es is written in typescript and therefore will always support typescript

how to contribute

feel free to submit pull requests, just please provide clear notes as to what your update will change. Pull requests that cause tests to fail will not be accepted.

how to install

you will need npm. Then install this library with

npm install cqrs-with-es --save

cqrs

to start writing your own typescript cqrs application, you will need an application service, to which you register command handlers and views

import {ApplicationService, IAmACommandHandler, DomainService, IAmACommand, View, AggregateRoot} from "cqrs-with-es";

class SomeView extends View{
    name = "SomeView"; // subscribers can get updates for this view

    stuff = 0;

    handle(event: IAmADomainEvent){
        var self = this;
        switch(event.name){
            case "SomeEvent":
                self.stuff++;
                return;
        }
    }
}

export class SomeAggregateRoot extends AggregateRoot{
    doStuff(command){
        //do something
    }

    applyEvent(event){
        switch(event.Name){
            //when action applied, do something here
            default:
                return;
        }
    }
}

class SomeCommandHandler implements IAmACommandHandler{

    commandNames = ["SomeCommand"]; // this handler will handle commands with these names

    handle(command, domainService: DomainService, callback: () => void){
        domainService.getAggregateRoot(SomeAggregateRoot, (someAggregateRoot: SomeAggregateRoot) => {
            someAggregateRoot.doStuff(command);
        }, "someAggregateID");
    }
}

var appService = ApplicationService.Instance;

appService.registerCommandHandler(SomeCommandHandler);
appService.registerView(SomeView);

To subscriber to a view

appService.subscribe("SomeView", (view: SomeView) => {
    //do something with the new view;
});

To handle a command

appService.handleCommand(new SomeCommand())

To validate a command from views

class TestCommandValidator extends CommandValidator{

    commandNames = [COMMAND_NAME];

    validate(command: IAmACommand){
        // getViewByName fetches view from application service
        this.getViewByName(viewName, (view: TestView)=> {
            if(view.hasSomeUnexpectedValue){
                throw new DomainError("oh noes, I didn't expect that!");
            }
        });
    }
}
ApplicationService.Instance.registerCommandValidator(TestCommandValidator);

replay events!

testApplicationService.replayEvents();

apply events from external sources

testApplicationService.storeEvent(new TestEvent("123"));

latest changes