Design Patterns: Proxy

The proxy design pattern is a layer that prevents you from instantiating heavy objects that will not be needed at a certain time.

The proxy pattern could be used to:

• prevent loading unnecessary resources
• access real data in a remote location
• prevent control from accessing non-declared members/methods

One example of the proxy structure could be the following:

I can have a proxy to access a store, if the store is closed it shouldn't even bother loading unnecessary resources.

public interface IStore
{
    void ListItems();
}

public class ProxyStore : IStore
{
    private RealStore realStore;

    public void ListItems()
    {
        if (DateTime.Now.Hour >= 6 && DateTime.Now.Hour <= 10)
        {
            if (realStore == null)
            {
                realStore = new RealStore();
            }

            realStore.ListItems();
        }
        else
        {
            Console.WriteLine("We're closed!");
        }
    }
}
public class RealStore : IStore
{
    public void ListItems()
    {
        Console.WriteLine("Heavy graphics Weapon 1");
        Console.WriteLine("Heavy graphics Weapon 2");
        Console.WriteLine("Heavy graphics Weapon 3");
        Console.WriteLine("Heavy graphics Weapon 4");
        Console.WriteLine("Heavy graphics Weapon 5");
    }
}

This example is something we can see in Assassins's Creed where this pattern might have been used. In an early game there is a shop that has many unavailable options. Instead of loading all the resources required for the items it uses a proxy saying there is nothing available, so it saves many resources.

Proxy Design Pattern - Assassins's Creed