Templates

Spawning a level’s worth of goblins means building the same Health/Enemy shape over and over. EntityTemplate defines it once, then each spawn instantiates it.

Defining a template

var goblinTemplate = new EntityTemplate()
    .AddComponent(new Health { Current = 10, Max = 10 })
    .AddTag<Enemy>();

Or subclass it for a named, hand-authored prefab instead of building one at runtime:

public sealed class GoblinTemplate : EntityTemplate
{
    public GoblinTemplate()
    {
        AddComponent(new Health { Current = 10, Max = 10 });
        AddTag<Enemy>();
    }
}

Instantiating it

world.Commands.CreateEntity(goblinTemplate);

Returns the same chainable EntityView a plain CreateEntity() does, so you can keep adding to this one instance on top of what the template already set:

Entity eliteGoblin = world.Commands.CreateEntity(goblinTemplate)
    .AddTag<Elite>();

For many at once:

Entity[] goblins = world.Commands.CreateEntity(goblinTemplate, 20);

Child subtrees

var swordTemplate = new EntityTemplate().AddComponent(new Weapon { Damage = 5 });
goblinTemplate.AddChild(swordTemplate);

Instantiating goblinTemplate now instantiates the sword too, connected via the Parent relation, in one archetype move per node. swordTemplate is reusable from other parents as well, each instantiation gets its own independent entities.

Note

Batch instantiation (CreateEntity(template, count)) doesn’t support templates with children, each child is a distinct set of entities per instance. Call CreateEntity(template) once per instance instead.

Frozen after first use

A template is mutable until the moment it’s first instantiated, then further AddComponent/AddTag/AddChild calls throw. Build the whole shape before handing it to CreateEntity the first time.

Next

Templates and relations both shape entities you already know about ahead of time. For state that belongs to no entity at all, see Resources.