如何让两个类引用相同的对象列表？

Question

I have 3 classes (Rawmaterial, RawmaterialRepository and Storage) and I would like to know how can I do so that the Storage class has as an attribute the same list created for RawmaterialRepository? In the class program I instantiated the wood and repository objects and added wood to the repository using the addRawmaterial method. Finally I instantiated storage1 and called the StockAlert method but it is not working for me. An error appears saying that the list in the Warehouse class is empty. This is my code.

public class Rawmaterial
{
    public string name;
    public int stock;

    public Rawmaterial(string name, int stock)
    {
        this.name = name;
        this.stock = stock;
    }
}
public class RawmaterialRepository
{
    public List<Rawmaterial> listRM = new List<Rawmaterial>();
    public RawmaterialRepository()
    {
        listRM = new List<Rawmaterial>();
    }
    public void addRawmaterial(Rawmaterial rawmaterial)
    {
        listRM.Add(rawmaterial);
    }
}
public class Storage
{
    public string name;
    public RawmaterialRepository listRM;
    public Storage(string name)
    {
        this.name = name;
        listRM = ; //this is a problem
    }

    public void StockAlert()
    {
        foreach (Rawmaterial rawmaterial in listRM.listRM) //this is a problem
        {
            if (rawmaterial.stock  <= 10)
            {
                Console.WriteLine("Sotck Alert");
            } 
        }
    }
}
class Program
{
    static void Main(string[] args)
    {
        Rawmaterial wood = new Rawmaterial("wood", 300) ;
        RawmaterialRepository repository = new RawmaterialRepository();
        repository.addRawmaterial(wood);
        Storage storage1 = new Storage("storage1");
        storage1.StockAlert();
}

PS Could you help me? I'm new to this.

Answer 1

You can pass your repository to storage in the storage constructor:

public Storage(string name, RawmaterialRepository listRM)
    {
        this.name = name;
        this.listRM = listRM; //this is a problem
    }

and then in Main

Storage storage1 = new Storage("storage1", repository );

Answer 2

You want to use a resource called "pass by reference"... The default behavior of C# is to pass-by-reference objects of custom classes, although you can make that explicit with the ref keyword

When you pass by reference, the object reference is passed (ie the memory location where the object is stored), such that inside the function or other class you do not create a new object, you only work with the one you had from the outside world.

Just for reference, in python the default behavior is also pass-by-reference.

public class Storage
{
        public string name;
        public RawmaterialRepository listRM;
        public Storage(string name, ref RawmaterialRepository repository )
        {
            this.name = name;
            listRM = repository; //this will be a reference to the same memory you created outside
        }
        public void StockAlert()
        {
        foreach (Rawmaterial rawmaterial in listRM.listRM)     //this is a problem
        {
                if (rawmaterial.stock  <= 10)
                {
                    Console.WriteLine("Sotck Alert");
                } 
            }
        }
}
class Program
{
    static void Main(string[] args)
    {
        Rawmaterial wood = new Rawmaterial("wood", 300) ;
        RawmaterialRepository repository = new         RawmaterialRepository();
        repository.addRawmaterial(wood);
        Storage storage1 = new Storage("storage1", repository); // just pass the object normally
        storage1.StockAlert();
}