Accessing entities via aggregate root: simple exam

问题:

Can you show simple example of accessing the contents of an entity in an aggregate via ita aggregate root? I am not clear on how you would represent the Aggregate permissions to reflect these concepts. tia.

回答1:

You typically would encapsulate this in commands that the Aggregate exposes on its contract.

For example, with an Order Aggregate, you might add OrderLines using data obtained from your GUI.

// This is the Order Aggregate Root
public class Order
{
    private readonly int id;
    private readonly Customer customer; // Customer is another Aggregate
    private readonly IList<OrderLine> orderLines;
    private readonly IOrderLineFactory orderLineFactory;

    public Order(int id, Customer customer, IOrderLineFactory orderLineFactory)
    {
        this.id = id;
        this.customer = customer;
        this.orderLines = new List<OrderLine>();
        this.orderLineFactory = orderLineFactory;
    }

    public void AddOrderLine(Item item, int quantity)
    {
        OrderLine orderLine = orderLineFactory.Create(this, item, quantity);
        orderLines.Add(orderLine);
    }
}