javascript - 如何在 Screeps 对象中实现继承？

Question

我已经研究 Screeps 一段时间了，昨晚我决定通过从 Creep 主类派生两个类 Miner 和 Transporter，将我的一些行为纳入类层次结构。但是，每当我做

console.log(_.functions(minerInstance));

我得到的函数列表和我做的时候完全一样

console.log(_.functions(transporterInstance));

有人可以告诉我我是否做错了什么，或者我是否真的遇到了我的代码运行环境的限制？ 这是我的代码:

////////////////////////////
// Creep.js
var Creep = function(creep, room) {
    this.creep = creep;
    this.room = room;
    this.name = creep.name;
    this.id = creep.id;
};

module.exports = Creep;

Creep.prototype = {
    tick: function() {
        console.log("Base class implementation of tick(), should never happen.");
    },

    getRole: function() {
        return this.creep.memory.role;
    }
};

////////////////////////////
// Miner.js
var Creep = require("Creep");

var Miner = function(creep, room) {
    this.base = Creep;
    this.base(creep, room);
    //Creep.call(this, creep, room);
};

module.exports = Miner;

Miner.prototype = Creep.prototype;

Miner.prototype.tick = function() {
    var creep = this.creep;

    if (creep.memory.activity === undefined || creep.memory.activity === "") {
        var target = creep.pos.findNearest(Game.SOURCES_ACTIVE);
        this.mine(creep, target);
    }

    var act = creep.memory.activity;
    if (act == "mine") {
        var target = this.getTarget(creep);
        if (target !== undefined) {
            if (creep.energy < creep.energyCapacity) {
                creep.moveTo(target);
                creep.harvest(target);
            } else {
                console.log("Write dump to truck code");
                /*var trucks = find.transporterInRange(creep, 1);
                if (trucks.length)  {
                    creep.moveTo(trucks[0]);
                    var amount = trucks[0].energyCapacity - trucks[0].energy;
                    creep.transferEnergy(trucks[0], amount);
                }*/
            }
        }
    }
};

Miner.prototype.mine = function(creep, target) {
    creep.memory.target = target.id;
    creep.memory.activity = "mine";        
};

Miner.prototype.getTarget = function(creep) {
    return Game.getObjectById(creep.memory.target);
};

////////////////////////////
// Transporter.js
var Creep = require("Creep");

var Transporter = function(creep, room) {
  Creep.call(this, creep, room);
};

module.exports = Transporter;

Transporter.prototype = Creep.prototype;

Transporter.prototype.tick = function() {
  var creep = this.creep;
    if (creep.energy < creep.energyCapacity) {
        var miner = this.room.findByRole(creep, "miner");
        console.log(miner);
        if (miner !== null) {
            //console.log(miner[0].name);
            //creep.moveTo(miner);

        } else
            console.log("no miners found");
    } else {
        console.log("moving to drop");
        //var drop = find.nearestEnergyDropOff(creep);
        //creep.moveTo(drop);
        //creep.transferEnergy(drop);
    }
};

Answer 1

用这条线...

Miner.prototype = Creep.prototype;

...你告诉 JS 这两个原型(prototype)实际上是同一个对象。因此，Miner.prototype 的任何更新也会影响 Creep.prototype。

一种可能的方法是在建立原型(prototype)之间的链接时使用Object.create。这是一个简化的例子:

function Foo(a) {
   this.a = a; 
}

Foo.prototype.tick = function() { console.log('Foo ticks'); };
Foo.prototype.tock = function() { console.log('Foo tocks'); };

function Bar(a, b) {
    this.base = Foo;
    this.base(a);
    this.b = b;
}

Bar.prototype = Object.create(Foo.prototype);
// as you inherit all the properties, you'll have to reassign a constructor
Bar.prototype.constructor = Bar;
Bar.prototype.tick = function() { console.log('Bar ticks'); };

var f = new Foo(1);
f.tick(); // Foo ticks
f.tock(); // Foo tocks
console.log(f); // Foo { a=1, ... }

var b = new Bar(1, 2);
b.tick(); // Bar ticks
b.tock(); // Foo tocks
console.log(b); // Bar { a=1, b=2, ... }