CODEWITHSUNDEEP
c#variablesobjecttypeof
user1494136
user1494136

Reputation: 89

variable object in c#

i have a class called gameObject and one of it's properties in called component and is of type object:

public object component;

and i'm trying to use this object to act as an object that can hold object of any class you give it. for example

unit c = new unit(...)
gameObject test = new gameObject(...)
test.component = c;

and i want to use the c object through the component object. for example

if(test.component==typeof(unit))
    test.component.Draw();//draw is a function of the unit object

is this possible to do? and how do i do it?

Upvotes: 3

Views: 599

Answers (6)

Agent_L
Agent_L

Reputation: 5411

As others said - you can cast everything to and from Object. But you should use some base class of interface to make sure no one will send you Int32 or some other unsuspected type. But if all supported types have some common method, it's even better to put it in interface. So you can Draw() anything without casting, not even wondering what it really is.

Variant with empty interface just enforcing proper type:

interface IComponent
{
}
class unit : IComponent
{
    //...
}
class enemy : IComponent
{
    //...
}
class gameObject
{
    IComponent component;//now only objects inheriting IComponent can be assigned here

    public void DrawComponent()
    {
        unit u = component as unit;
        if (u != null) {
            u.Draw();
        }
        enemy e = component as enemy;
        if (e != null) {
            e.DrawIfVisible();
        }
    }
}

Variant with interface declaring common features:

interface IDrawable
{
    void Draw();
}
class unit : IDrawable
{
    public void Draw(){;}
    //...
}
class enemy : IDrawable
{
    public void Draw(){;}
    //...
}


class gameObject
{
    IDrawable component;

    public void DrawComponent()
    {
        //now you don't need to care what type component really is
        //it has to be IDrawable to be assigned to test
        //and because it is IDrawable, it has to have Draw() method
        if (component != null) {
            component.Draw();
        }
    }
}

Upvotes: 1

davioooh
davioooh

Reputation: 24666

To use specific behaviour of an object you have to cast it to its specific type. Referencig it with an object variable you can use it only as an object instance.

Upvotes: 0

Sergey Kalinichenko
Sergey Kalinichenko

Reputation: 726489

typeof(unit) is an object too, and it is different from component. You should do component.GetType() instead:

if(test.component.GetType()==typeof(unit))

This does not check for derived types, but this does:

if(test.component is unit)

Still, this does not let you call Draw without casting. The easiest way to check and cast at the same time is as follows:

unit u = test.component as unit;
if (u != null) {
    u.Draw();
}

Upvotes: 7

flayn
flayn

Reputation: 5322

Use an interface and make the unit class implement that interface. Define the Draw() method in the interface and declare the component as the type of the interface you defined.

public interface IDrawable
{
 void Draw();
}

public IDrawable component;

public class unit : IDrawable
...

Upvotes: 5

John Smith
John Smith

Reputation: 86

if (test.component is unit) ((unit)(test.component)).Draw();

Upvotes: 3

hcb
hcb

Reputation: 8357

Yes, it's called casting. Like this:

if(test.component is unit)
  ((unit)test.component).Draw();

Upvotes: 5

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