JavaScriptでDCI的なものを実装してみた例

gistfile1.txt

// 銀行口座
var BankAccount = function (balance) { this.balance = balance; };
BankAccount.prototype.increase = function (money) { this.balance += money; };
BankAccount.prototype.decrease = function (money) { this.balance -= money; };

// ロール: 送信側
var Sender = function () {};
Sender.prototype.send = function (money, to) {
    this.decrease(money);
    to.onReceived(money, this);
};

// ロール：受信側
var Receiver = function () {};
Receiver.prototype.onReceived = function (money, to) {
    this.increase(money);
};

// コンテキスト: 口座間送金
var TransferContext = function (from, to) {
    Object.keys(TransferContext.prototype).filter(function (key) {
        return 'function' == typeof this[key];
    }.bind(this)).forEach(function (key) {
        var func = this[key];
        this[key] = function () {
            var mixin = function (obj, ctx) {
                var proto = obj.__proto__;
                obj.__proto__ = ctx;
                obj.__proto__.__proto__ = proto;
            }
            var cleanup = function (obj) {
                obj.__proto__ = obj.__proto__.__proto__;
            }
            mixin(from, Sender.prototype);
            mixin(to, Receiver.prototype);

            func.apply(this, arguments);

            cleanup(from);
            cleanup(to);
        };
    }.bind(this));
    this.from = from;
    this.to = to;
};
TransferContext.prototype.transfer = function (money) {
    this.from.send(money, this.to);
};

var from = new BankAccount(10);
var to = new BankAccount(10);
(new TransferContext(from, to)).transfer(10);
console.log(from.balance, to.balance); // 0 20
console.log(from.send, to.onReceived); // undefined undefined