Miscellaneous improvements/changes (#138)

* Add the ability to get all component types registered

* Tags: changed to a single string: can name them as you create them

* Update tag.go

* Fix test

README.md

@@ -230,25 +230,44 @@ query.Each(world, func(entry *donburi.Entry) {
   }
 
 })
+```
+
+## Ordered Queries
+Sometimes you may need to iterate a query in a specific order. Donburi supports this through the `OrderedQuery[T]` type.
+In order to use this, the component must implement the IOrderable interface:
+```go
+type IOrderable interface {
+	Order() int
+}
+```
+
+Example:
+Here we assume the `spatial.TransformComponent` implements `Order()`.
+```go
+q := donburi.NewOrderedQuery[spatial.Transform](
+filter.Contains(sprite.Component, spatial.TransformComponent))
 
+q.EachOrdered(w, spatial.TransformComponent, func(entry *donburi.Entry) {
+	// This will be iterated according to the spatial.TransformComponent's Order() function.
+})
 ```
 
 ### Tags
 
-One or multiple "Tag" components can be attached to an entity. "Tag"s are just components with no data.
+One or multiple "Tag" components can be attached to an entity. "Tag"s are just components with a single name string as data.
 
 Here is the utility function to create a tag component.
 
 ```go
 // This is the utility function to make tag component
-func NewTag() *ComponentType {
-  return NewComponentType(struct{}{})
+func NewTag(name string) *ComponentType {
+  return NewComponentType(Tag(name))
 }
 ```
 Since "Tags" are components, they can be used in queries in the same way as components as follows:
 
 ```go
-var EnemyTag = donburi.NewTag()
+var EnemyTag = donburi.NewTag("Enemy")
 world.CreateMany(100, EnemyTag, Position, Velocity)
 
 // Search entities with EnemyTag

component.go

@@ -139,20 +139,31 @@ func (c *ComponentType[T]) validateDefaultVal() {
 }
 
 var nextComponentTypeId component.ComponentTypeId = 1
+var globalComponentTypes []component.IComponentType
 
 // NewComponentType creates a new component type.
 // The argument is a struct that represents a data of the component.
 func newComponentType[T any](s T, defaultVal interface{}) *ComponentType[T] {
+	typ := reflect.TypeOf(s)
 	componentType := &ComponentType[T]{
 		id:         nextComponentTypeId,
-		typ:        reflect.TypeOf(s),
-		name:       reflect.TypeOf(s).Name(),
+		typ:        typ,
+		name:       typ.Name(),
 		defaultVal: defaultVal,
 	}
 	componentType.query = NewQuery(filter.Contains(componentType))
 	if defaultVal != nil {
 		componentType.validateDefaultVal()
 	}
 	nextComponentTypeId++
+	globalComponentTypes = append(globalComponentTypes, componentType)
 	return componentType
 }
+
+// AllComponentTypes returns all IComponentTypes created at that point in time.
+// All types created using `donburi.NewComponentType()` will be in this list.
+// This is useful if you want to use introspection on the ECS, such as when doing (de)serialization.
+// This includes components which are not in any archetypes or on any entity.
+func AllComponentTypes() []IComponentType {
+	return globalComponentTypes
+}

ecs/layer.go

@@ -68,7 +68,7 @@ func getLayer(layerID LayerID) *layer {
 	if layers[layerID] == nil {
 		layers[layerID] = &layer{
 			id:  layerID,
-			tag: donburi.NewTag().SetName(fmt.Sprintf("Layer%d", layerID)),
+			tag: donburi.NewTag(fmt.Sprintf("Layer%d", layerID)),
 		}
 	}
 	return layers[layerID]

entry_test.go

@@ -47,7 +47,7 @@ func TestGetComponents(t *testing.T) {
 	donburi.SetValue(entryA, velocity, veData)
 
 	gots := donburi.GetComponents(entryA)
-	wants := []interface{}{trData, veData, struct{}{}}
+	wants := []interface{}{trData, veData, donburi.Tag("")}
 
 	if len(gots) != len(wants) {
 		t.Fatalf("got: %v, want: %v", gots, wants)

tag.go

@@ -1,7 +1,19 @@
 package donburi
 
+type Tag string
+
 // NewTag is an utility to create a tag component.
 // Which is just an component that contains no data.
-func NewTag() *ComponentType[struct{}] {
-	return NewComponentType[struct{}]()
+// Specify a string as the first and only parameter if you wish to name the component.
+func NewTag(opts ...any) *ComponentType[Tag] {
+	if len(opts) == 0 {
+		return NewComponentType[Tag]()
+	}
+	first, ok := opts[0].(string)
+	if !ok {
+		return NewComponentType[Tag]()
+	}
+	c := NewComponentType[Tag](Tag(first))
+	c.SetName(first)
+	return c
 }