工厂模式的替代方案，可能有数百个小类

Question

I'm working on a small game/simulator, written in GoLang, in which there will be potentially hundreds of abilities. For each player, they will have between 1 and 3 abilities. I'll have these stored with either strings or Ids. What is the best way to instantiate these abilities. Normally I'd use a factory class, but with as many as I'm talking about, I'm not sure that's the best way.

Answer 1

You can still use the factory pattern, it's what the encoding/gob package uses.

playground: http://play.golang.org/p/LjR4PTTCvw

For example in abilities.go you could have

type Ability interface {
    Execute()
}

var abilities = struct {
    m map[string]AbilityCtor
    sync.RWMutex
}{m: make(map[string]AbilityCtor)}

type AbilityCtor func() Ability

func Register(id string, newfunc AbilityCtor) {
    abilities.Lock()
    abilities.m[id] = newfunc
    abilities.Unlock()
}

func GetAbility(id string) (a Ability) {
    abilities.RLock()
    ctor, ok := abilities.m[id]
    abilities.RUnlock()
    if ok {
        a = ctor()
    }
    return
}

Then for each ability (in separate files probably) you could do something like :

type Fireball struct{}

func (s *Fireball) Execute() {
    fmt.Println("FIREBALL EXECUTED")
}

func init() {
    Register("Fireball", func() Ability {
        return &Fireball{}
    })
}

func main() {
    if fireball := GetAbility("Fireball"); fireball != nil { //could be nil if not found
        fireball.Execute()
    }
}