babel-dci demo

Source

function TransferMoney(source: Account, destination: Account, amount: number) {
    banker = this;
    banker.transfer();

    role banker {
        transfer() {
            source.withdraw();
            destination.deposit();
        }
    }

    role source {
        withdraw() {
            if (this.balance < amount) {
                throw Error('Insufficient funds');
            }
            this.decreaseBalance(amount);
        }
    }
    
    role destination {
        deposit() {
            this.increaseBalance(amount);
        }
    }
    
    role amount {}
}

context Account {
    constructor(ledgers: ?Array<LedgerEntry>) {
        if (!ledgers) ledgers = [];
    }
    
    increaseBalance(amount: number) {
        ledgers.addEntry('depositing', amount);
    }
    
    decreaseBalance(amount: number) {
        ledgers.addEntry('withdrawing', 0 - amount);        
    }
    
    get balance(): number {
        return ledgers.getBalance();
    }
    
    role ledgers {
        addEntry(message: string, amount: number) {
            ledgers.push(new LedgerEntry(message, amount));
        }
        
        getBalance(): number {
            return ledgers.reduce((sum, ledger) => (
                sum + ledger.amount
            ), 0);
        }
    }
}

function LedgerEntry(message: string, amount: number) {
    this._message = message;
    this._amount = amount;
}
LedgerEntry.prototype = {
    constructor: LedgerEntry,
    
    get message(): string {
        return this._message;
    },
    
    get amount(): number {
        return this._amount;
    }
};

const source = new Account();
source.increaseBalance(30);
const dest = new Account();
dest.increaseBalance(30);
TransferMoney(source, dest, 10);

console.log('source balance', source.balance);
console.log('destination balance', dest.balance);

Output

Loading...