Golang享元模式管理大量重复对象技巧

package main

import (
    "fmt"
    "sync"
)

// TreeModel 是享元（内在状态），代表树的共享数据
type TreeModel struct {
    ID        string
    Texture   string
    Mesh      string
    Collision string
}

// Draw 方法展示如何使用内在状态
func (tm *TreeModel) Draw(x, y, z float64, scale float64, rotation float64) {
    fmt.Printf("Drawing %s at (%.1f, %.1f, %.1f) with scale %.1f, rotation %.1f. Model: Texture=%s, Mesh=%s\n",
        tm.ID, x, y, z, scale, rotation, tm.Texture, tm.Mesh)
}

// TreeModelFactory 是享元工厂，负责创建和管理TreeModel
type TreeModelFactory struct {
    models map[string]*TreeModel
    mu     sync.Mutex // 保护map的并发访问
}

// GetTreeModel 获取或创建TreeModel享元
func (f *TreeModelFactory) GetTreeModel(modelID string) *TreeModel {
    f.mu.Lock()
    defer f.mu.Unlock()

    if model, ok := f.models[modelID]; ok {
        return model
    }

    // 模拟创建TreeModel的开销
    fmt.Printf("Creating new TreeModel: %s\n", modelID)
    newModel := &TreeModel{
        ID:        modelID,
        Texture:   fmt.Sprintf("texture_%s.png", modelID),
        Mesh:      fmt.Sprintf("mesh_%s.obj", modelID),
        Collision: fmt.Sprintf("collision_%s.json", modelID),
    }
    f.models[modelID] = newModel
    return newModel
}

// NewTreeModelFactory 创建一个新的TreeModelFactory
func NewTreeModelFactory() *TreeModelFactory {
    return &TreeModelFactory{
        models: make(map[string]*TreeModel),
    }
}

// Tree 是客户端对象，包含外在状态和对享元的引用
type Tree struct {
    model *TreeModel // 享元引用
    x, y, z float64  // 外在状态
    scale   float64  // 外在状态
    rotation float64 // 外在状态
}

// NewTree 创建一棵树
func NewTree(factory *TreeModelFactory, modelID string, x, y, z, scale, rotation float64) *Tree {
    model := factory.GetTreeModel(modelID)
    return &Tree{
        model: model,
        x:     x,
        y:     y,
        z:     z,
        scale: scale,
        rotation: rotation,
    }
}

// Draw 方法使用享元和外在状态来渲染树
func (t *Tree) Draw() {
    t.model.Draw(t.x, t.y, t.z, t.scale, t.rotation)
}

func main() {
    factory := NewTreeModelFactory()

    // 创建大量树，但只使用少数几种TreeModel
    trees := make([]*Tree, 0, 1000)
    for i := 0; i < 500; i++ {
        // 500棵橡树
        trees = append(trees, NewTree(factory, "OakTree", float64(i)*10, 0, float64(i)*5, 1.0, float64(i)*0.1))
        // 500棵松树
        trees = append(trees, NewTree(factory, "PineTree", float64(i)*12, 0, float64(i)*6, 0.8, float64(i)*0.2))
    }

    // 模拟渲染前几棵树
    fmt.Println("\n--- Drawing some trees ---")
    trees[0].Draw()
    trees[501].Draw()
    trees[10].Draw()
    trees[511].Draw()

    fmt.Printf("\nTotal unique TreeModels created: %d\n", len(factory.models))
    // 期望输出是2，因为只有"OakTree"和"PineTree"两种模型被创建
}

TreeModelFactory

TreeModel

modelID

TreeModel

new(Object)

&Object{}