On Fri, Aug 2, 2019 at 9:41 AM Coda Highland <chighland@gmail.com
<mailto:chighland@gmail.com>> wrote:
On Fri, Aug 2, 2019 at 2:33 AM Egor Skriptunoff
<egor.skriptunoff@gmail.com <mailto:egor.skriptunoff@gmail.com>>
wrote:
On Fri, Aug 2, 2019 at 12:19 AM Soni "They/Them" L. wrote:
> On 2019-08-01 6:05 p.m., Egor Skriptunoff wrote:
>> Could you provide an example to show benefits of traits?
>> What kinds of tasks traits solve better than conventional
>> 'objects-and-methods' approach?
>>
>
> I recommend reading
https://en.wikipedia.org/wiki/Entity_component_system
(Well, besides reading that, I recommend actually checking
out Rust and
using it for a while. You'll see what I mean.)
Could you just show a simple example from real-life
programming where using traits is better than not using them?
Such example should be understandable by any Lua programmer
(without Rust knowledge).
If you can't provide such example then why Lua users might
want to use Cratera?
If your own example on SO satisfies you, then let me rewrite it
using standard Lua syntax (not Cratera traits because I'm not
familiar enough):
all_entities = {]
function HealthRegen(self, entity, dt)
self.current_hp = math.min(
self.max_hp,
self.current_hp + self.max_hp * dt / (5*60)
)
end
traits = {
Health = function(hp) return { max_hp = hp, current_hp = hp,
update = HealthRegen },
Velocity = function(max) return { max_speed = max, speed_x = 0,
speed_y = 0 }
}
function Instantiate(type)
local obj = {}
for trait, param in pairs(type) do
obj[trait] = traits[trait](param)
end
table.insert(all_entities, obj)
return obj
end
Player = { Health = 42, Velocity = 1.0 }
Monster = { Health = 100, Velocity = 2.5 }
player = Instantiate(Player)
monster = Instantiate(Monster)
function update(dt)
for _, entity in pairs(all_entities) do
if entity.update then entity:update(dt) end
for _, trait in pairs(entity) do
if trait.update then trait:update(entity, dt) end
end
end
end
Forgot to mention...
function HealthDamage(self, entity, amount)
self.current_hp = self.current_hp - amount
if self.current_hp <= 0 then
self.current_hp = 0
if entity.OnDeath then entity:OnDeath() end
end
end
monster.Health:damage(monster, 10)
This isn't quite compatible with how Cratera's syntax does it, because
at this point I would want to write monster:[Health]:damage(10) and I
can't do that. But it should still get the point across.
/s/ Adam
