goecs

README

goecs

A simple Go ECS

Info

Entity–component–system (ECS) is an architectural patter that follows the composition over inheritance principle that allows greater flexibility in defining entities where every object in a world.

Every entity consists of one or more components which contains data or state. Therefore, the behavior of an entity can be changed at runtime by systems that add, remove or mutate components.

This eliminates the ambiguity problems of deep and wide inheritance hierarchies that are difficult to understand, maintain and extend.

Common ECS approaches are highly compatible and often combined with data-oriented design techniques.

For a more in deep read on this topic I could recommend this article.

Example

Run it on the Go Playground

package main

import (
	"github.com/juan-medina/goecs/entity"
	"github.com/juan-medina/goecs/world"
	"log"
	"reflect"
)

// Simple Usage
func main() {
	// creates the world
	wld := world.New()

	// add our movement system
	wld.AddSystem(MovementSystem)

	// add a listener
	wld.Listen(ChangePostListener)

	// add a first entity
	wld.Add(entity.New(
		Pos{X: 0, Y: 0},
		Vel{X: 1, Y: 1},
	))

	// this entity shouldn't be updated
	wld.Add(entity.New(
		Pos{X: 2, Y: 2},
	))

	// add a third entity
	wld.Add(entity.New(
		Pos{X: 2, Y: 2},
		Vel{X: 3, Y: 3},
	))

	// ask the world to update
	if err := wld.Update(0.5); err != nil {
		log.Fatalf("error on update %v", err)
	}

	// print the world
	log.Printf("world: %v", wld)
}

// MovementSystem is a simple movement system
func MovementSystem(wld *world.World, delta float32) error {
	// get all the entities that we need to update, only if they have Pos & Vel
	for it := wld.Iterator(PosType, VelType); it != nil; it = it.Next() {
		// get the values
		ent := it.Value()
		pos := ent.Get(PosType).(Pos)
		vel := ent.Get(VelType).(Vel)

		// calculate new pos
		npos := Pos{
			X: pos.X + (vel.X * delta),
			Y: pos.Y + vel.Y*delta,
		}

		// signal the change
		if err := wld.Signal(PosChangeSignal{From: pos, To: npos}); err != nil {
			return err
		}

		// set the new pos
		ent.Set(npos)
	}

	return nil
}

// ChangePostListener listen to PosChangeSignal
func ChangePostListener(wld *world.World, signal interface{}, delta float32) error {
	switch s := signal.(type) {
	case PosChangeSignal:
		// print the change
		log.Printf("pos change from %v to %v", s.From, s.To)
	}
	return nil
}

// Pos represent a 2D position
type Pos struct {
	X float32
	Y float32
}

// PosType is the reflect.Type of Pos
var PosType = reflect.TypeOf(Pos{})

// Vel represent a 2D velocity
type Vel struct {
	X float32
	Y float32
}

// VelType is the reflect.Type of Vel
var VelType = reflect.TypeOf(Vel{})

// PosChangeSignal is a signal that a Pos has change
type PosChangeSignal struct {
	From Pos
	To   Pos
}

This will output:

world: World{view: View{entities: [Entity{id{0},main.Pos{0.5 0.5},main.Vel{1 1}},Entity{id{1},main.Pos{2 2}},Entity{id{2},main.Pos{3.5 3.5},main.Vel{3 3}}]}, systems: [{main.MovementSystem}] listeners: []}

Installation

go get -v -u github.com/juan-medina/goecs

License

    Copyright (C) 2020 Juan Medina

    Licensed under the Apache License, Version 2.0 (the "License");
    you may not use this file except in compliance with the License.
    You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

    Unless required by applicable law or agreed to in writing, software
    distributed under the License is distributed on an "AS IS" BASIS,
    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    See the License for the specific language governing permissions and
    limitations under the License.

Documentation

Overview

Package goecs is our public package

Example

Simple Usage

/*
 * Copyright (c) 2020 Juan Medina.
 *
 *  Permission is hereby granted, free of charge, to any person obtaining a copy
 *  of this software and associated documentation files (the "Software"), to deal
 *  in the Software without restriction, including without limitation the rights
 *  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 *  copies of the Software, and to permit persons to whom the Software is
 *  furnished to do so, subject to the following conditions:
 *
 *  The above copyright notice and this permission notice shall be included in
 *  all copies or substantial portions of the Software.
 *
 *  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 *  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 *  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 *  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 *  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 *  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 *  THE SOFTWARE.
 */

package main

import (
	"github.com/juan-medina/goecs/entity"
	"github.com/juan-medina/goecs/world"
	"log"
	"reflect"
)

// Simple Usage
func main() {
	// creates the world
	wld := world.New()

	// add our movement system
	wld.AddSystem(MovementSystem)

	// add a listener
	wld.Listen(ChangePostListener)

	// add a first entity
	wld.Add(entity.New(
		Pos{X: 0, Y: 0},
		Vel{X: 1, Y: 1},
	))

	// this entity shouldn't be updated
	wld.Add(entity.New(
		Pos{X: 2, Y: 2},
	))

	// add a third entity
	wld.Add(entity.New(
		Pos{X: 2, Y: 2},
		Vel{X: 3, Y: 3},
	))

	// ask the world to update
	if err := wld.Update(0.5); err != nil {
		log.Fatalf("error on update %v", err)
	}

	// print the world
	log.Printf("world: %v", wld)
}

// MovementSystem is a simple movement system
func MovementSystem(wld *world.World, delta float32) error {
	// get all the entities that we need to update, only if they have Pos & Vel
	for it := wld.Iterator(PosType, VelType); it != nil; it = it.Next() {
		// get the values
		ent := it.Value()
		pos := ent.Get(PosType).(Pos)
		vel := ent.Get(VelType).(Vel)

		// calculate new pos
		npos := Pos{
			X: pos.X + (vel.X * delta),
			Y: pos.Y + vel.Y*delta,
		}

		// signal the change
		if err := wld.Signal(PosChangeSignal{From: pos, To: npos}); err != nil {
			return err
		}

		// set the new pos
		ent.Set(npos)
	}

	return nil
}

// ChangePostListener listen to PosChangeSignal
func ChangePostListener(wld *world.World, signal interface{}, delta float32) error {
	switch s := signal.(type) {
	case PosChangeSignal:
		// print the change
		log.Printf("pos change from %v to %v", s.From, s.To)
	}
	return nil
}

// Pos represent a 2D position
type Pos struct {
	X float32
	Y float32
}

// PosType is the reflect.Type of Pos
var PosType = reflect.TypeOf(Pos{})

// Vel represent a 2D velocity
type Vel struct {
	X float32
	Y float32
}

// VelType is the reflect.Type of Vel
var VelType = reflect.TypeOf(Vel{})

// PosChangeSignal is a signal that a Pos has change
type PosChangeSignal struct {
	From Pos
	To   Pos
}