9.享元模式

约 281 字小于 1 分钟

2026-02-27

享元模式（Flyweight Pattern）的主要目的是通过共享可复用的内部状态，减少大量相似对象的内存占用

适合使用享元模式的场景

系统中存在大量细粒度对象，且大部分状态可共享
对象创建和存储成本高，内存压力明显
可以明确拆分“内部状态”和“外部状态”
希望通过对象池或缓存提升资源复用率

共享对象定义

type PieceColor = "black" | "white";

class ChessPieceType {
    constructor(
        public readonly name: string,
        public readonly color: PieceColor,
    ) {}
}

享元工厂与上下文对象

class ChessPieceFactory {
    private static pool = new Map<string, ChessPieceType>();

    static get(name: string, color: PieceColor): ChessPieceType {
        const key = `${name}-${color}`;
        if (!this.pool.has(key)) {
            this.pool.set(key, new ChessPieceType(name, color));
        }
        return this.pool.get(key)!;
    }

    static size(): number {
        return this.pool.size;
    }
}

class ChessPiece {
    constructor(
        private readonly type: ChessPieceType,
        private x: number,
        private y: number,
    ) {}

    draw(): void {
        console.log(`${this.type.color} ${this.type.name} at (${this.x}, ${this.y})`);
    }
}

使用示例

const p1 = new ChessPiece(ChessPieceFactory.get("pawn", "white"), 1, 2);
const p2 = new ChessPiece(ChessPieceFactory.get("pawn", "white"), 2, 2);
const p3 = new ChessPiece(ChessPieceFactory.get("pawn", "black"), 1, 7);

p1.draw();
p2.draw();
p3.draw();

console.log("共享对象数量:", ChessPieceFactory.size()); // 2