Node.js sample

This sample requires nodejs.

Start by creating a directory to house your code.

From a command line within your new directory, initialize a new project via:

• yarn: yarn init
• npm: npm init

Next, install peasy-js via:

• yarn: yarn add peasy-js.
• npm: npm install peasy-js.

Next create a data proxy by creating a file (personDataProxy.js) with the following content:

// personDataProxy.js

class PersonDataProxy {

  constructor() {
    this._data = [];
  }

  getById(id) {
    var person = this._findBy(id);
    return Promise.resolve(person);
  }

  getAll() {
    return Promise.resolve(this._data);
  }

  insert(data) {
    data.id = this._data.length + 1;
    var newPerson = Object.assign({}, data);
    this._data.push(newPerson);
    return Promise.resolve(data);
  }

  update(data) {
    var person = this._findBy(data.id);
    Object.assign(person, data);
    return Promise.resolve(data);
  }

  destroy(id) {
    var person = this._findBy(id);
    var index = this._data.indexOf(person);
    this._data.splice(index, 1);
    return Promise.resolve();
  }

  _findBy(id) {
    var person = this._data.filter((function(p) {
      return p.id === id;
    }))[0];
    return person;
  }

}

module.exports = PersonDataProxy;

Then, create a business service file (personService.js), which exposes CRUD commands responsible for subjecting data proxy invocations to business rules before execution:

// personService.js

var BusinessService = require('peasy-js').BusinessService;

class PersonService extends BusinessService {

  constructor(dataProxy) {
    super(dataProxy);
  }

}

module.exports = PersonService;

Now let's consume our PersonService by creating a file (example.js) with the following contents:

// example.js

var PersonDataProxy = require('./personDataProxy');
var PersonService = require('./personService');

var personService = new PersonService(new PersonDataProxy());
var command = personService.insertCommand({name: "James Morrison"});

command.execute().then(result => {
  if (result.success) {
    console.log(result.value); // prints the inserted object with the assigned id
  }
});

Testing it out from command line: node example.js

Let's create a business rule file (personNameRule.js) whose execution must be successful before the call to inject dataproxy.insert() function is invoked.

// personNameRule.js

var Rule = require('peasy-js').Rule;

class PersonNameRule extends Rule {

  constructor(name) {
    super();
    this.name = name;
    this.association = "name" // optional
  }

  _onValidate() {
    if (this.name === "Jimi Hendrix") {
      this._invalidate("Name cannot be Jimi Hendrix");
    }
    return Promise.resolve();
  }
}

module.exports = PersonNameRule;

And wire it up in our PersonService to ensure that it gets fired before inserts:

// personService.js

var BusinessService = require('peasy-js').BusinessService;
var PersonNameRule = require('./personNameRule');

class PersonService extends BusinessService {

  constructor(dataProxy) {
    super(dataProxy);
  }

  _getRulesForInsertCommand(person, context) {
    return Promise.resolve([
      new PersonNameRule(person.name)
    ]);
  }
}

module.exports = PersonService;

Testing it out ...

// example.js

var PersonDataProxy = require('./personDataProxy');
var PersonService = require('./personService');

var dataProxy = new PersonDataProxy();
var personService = new PersonService(dataProxy);

var command = personService.insertCommand({name: "Jimi Hendrix"});

command.execute().then(result => {
  if (result.success) {
    console.log(result.value);
  } else {
    console.log(result.errors[0]); // prints {association: "name", message: "Name cannot be Jimi Hendrix"}
  }
});

Testing it out from command line: node example.js

Let's create one more rule (validCityRule.js), just for fun:

// validCityRule.js

var Rule = require('peasy-js').Rule;

class ValidCityRule extends Rule {

  constructor(city) {
    super();
    this.city = city;
    this.association = "city" // optional
  }

  _onValidate() {
    if (this.city === "Nowhere") {
      this._invalidate("Nowhere is not a city");
    }
    return Promise.resolve();
  }
}

module.exports = ValidCityRule;

We'll associate this one with inserts too:

// personService.js

var BusinessService = require('peasy-js').BusinessService;
var PersonNameRule = require('./personNameRule');
var ValidCityRule = require('./validCityRule');

class PersonService extends BusinessService {

  constructor(dataProxy) {
    super(dataProxy);
  }

  _getRulesForInsertCommand(person, context) {
    return Promise.resolve([
      new PersonNameRule(person.name),
      new ValidCityRule(person.city)
    ]);
  }
}

module.exports = PersonService;

And test it out ...

// example.js

var PersonDataProxy = require('./personDataProxy');
var PersonService = require('./personService');

var dataProxy = new PersonDataProxy();
var personService = new PersonService(dataProxy);

var command = personService.insertCommand({name: "Jimi Hendrix", city: "Nowhere"});

command.execute().then(result => {
  if (result.success) {
    console.log(result.value);
  } else {
    console.log(result.errors[0]); // prints {association: "name", message: "Name cannot be Jimi Hendrix"}
    console.log(result.errors[1]); // prints {association: "city", message: "Nowhere is not a city"}
  }
});

Testing it out from command line: node example.js

Finally, let's pass in valid data and watch it be a success

// example.js

var PersonDataProxy = require('./personDataProxy');
var PersonService = require('./personService');

var dataProxy = new PersonDataProxy();
var personService = new PersonService(dataProxy);

var command = personService.insertCommand({name: "James Hendrix", city: "Madison"});

command.execute().then(result => {
  if (result.success) {
    console.log(result.value); // prints the inserted object with the assigned id
  } else {
    console.log(result.errors);
  }
});

Testing it out from command line: node example.js

Want to learn more?

• View this sample in TypeScript.
• View this sample consuming it from a browser.
• You can read in-depth coverage about peasy-js on the wiki.
• An entire business logic implementation using peasy-js can be viewed here. This sample application is an order entry / inventory management system written with peasy-js, react, angular (with TypeScript), mongoDB, nodejs, and express.