C＃ - 类实例化其他类？

Question

I'm a C# beginner and am struggling a little bit with how classes relate to one another.

I am trying to code up a very simple elevator simulation. I have a class for Elevator:

class Elevator
{
    public int currentFloor;

    public Elevator()
    {
        currentFloor = 0;
    }

    public void ascend()
    {
        currentFloor++;
    }

    public void descend()
    {
        currentFloor--;
    }
}

Very simple. This works, I can instantiate a new elevator object and have it go up and down, etc...

Now, I want to create a building object, so I created a new class for Buildings. However, I am now stuck - how do I add variable amounts of elevator objects to my buildings? For example, I might want to instantiate a building with 3 elevators, or another with 5...

I started creating a solutiomn where the building class has a List of elevators I can dynamically add to, but that seems so obtuse. So what I am looking for is something like:

Building office = new Building();
office.elevator1 = new Elevator();
office.elevator2 = new Elevator();

which obviously doesn't work because I don't have elevator1 and elevator2 declared in the Building class. What is the best/cleanest way to accomplish what I am looking to do? Also, what is this called? I Googled a ton of terms - class belongs to another class, instantiating a class from another class, similar terms with object instead of class... I've also looked over some of the elevator simulator code out there, but couldn't find anything dynamic like I'm looking for...

Answer 1

Having a List<Elevator> is quite appropriate here; it describes the real-world model very well.

Perhaps it would be better if it were an Elevator[] (in the sense that perhaps it should not be possible to change the number of installed elevators after the building has been erected), but that's not absolute.

In any case, the collection of elevators should be exposed as a read-only property of appropriate type because it doesn't make sense to swap it with another one.

Answer 2

You can add member of type equal to List<Elevator> nd inject inside constructor

Sample

public class Building
{
    private List<Elevator> yourList;
    public Building(List<Elevator> value)
    {
      yourList = value;
    }
}

Use case :

var list = new List<Elevator>();
list.Add
.....
var building = new Building(list);

Answer 3

Here's an alternative:

class Building
{
   public List<Elevator> Elevators { get; set; }

   public Building(params Elevator[] elevators)
   {
       Elevators = elevators.ToList();
   }
}

The you can do:

var building = new Building(new Elevator(), new Elevator(), new Elevator());

And add more later:

building.Elevators.Add(new Elevator());

Answer 4

Depends. Say your building will only ever have one elevator. You'd want to do something like this:

public class Building
{
    public Elevator Elevator { get; set; }
}

Then when you create the building like you did in your code above, you can do something like this:

office.Elevator = new Elevator();

You're new to C#, so you may not have really been exposed to Properties yet ( more reading ). Cliffs on Properties: they're creating a way for you to get and set data about your object. In this example, we're getting/setting the Elevator .

Now, if your building is going to have an unknown amount of elevators, you can't just write properties for Elevator1 to ElevatorInfinity. That's when you'll want to use a collection of some sort. As others have posted in here, you can do this like so:

public class Building
{
    public IList<Elevator> Elevators { get; set; }
}

And to add an elevator to your building:

// Make sure you instantiate the list! For practice, you should run this code without instantiating the list, so you can see what happens.
office.Elevators = new List<Elevator>();
office.Elevators.Add(new Elevator());

More reading on IList

Answer 5

I think you can override indexer. Of course, you should backbone it with List. Lists are ok.

namespace Tests_CSharp_Indexer
{
class Elevator
{
}

class Building
{

    public class ElevatorList
    {
        private List<Elevator> elevators = new List<Elevator>();

        public Elevator this[int i]
        {
            get
            {
                return elevators[i];
            }

            set
            {
                if (i == elevators.Count)
                {
                    elevators.Add(value);
                }
                else
                {
                    elevators[i] = value;
                }
            }
        }

        public int Count {
            get
            {
                return elevators.Count;
            }
        }
    }

    public readonly ElevatorList Elevators = new ElevatorList();

}

class Program
{
    static void Main(string[] args)
    {

        Building building = new Building();

        building.Elevators[0] = new Elevator();
        building.Elevators[1] = new Elevator();
        building.Elevators[2] = new Elevator();

        Console.Out.WriteLine(building.Elevators.Count);
    }
}
}