Say you have a class called Car. Now normally, if you wanted to set an instance of Car equal to another instance, you'd do this:
Car car1 = new Car();
Car car2 = new Car();
car1 = car2;
Now what if you wanted to have a method that did that?
Car
{
public void SetEqualToReference(Car reference)
{
this = reference;
}
}
And then you'd do
car1.SetEqualToReference(car2);
And car1 would be equal to car2. But as you know, that doesn't work. Is there a way to do something similar?
After reading your comment that saving and opening a serialized version of your object is what you really want to do I provide this answer.
The Save method is always the same:
class Car {
public void Save(String fileName) {
// Serialize the fields of the current instance to the file.
}
}
To initialize a new instance from the serialized data you can use a constructor:
class Car {
public void Car(String fileName) {
// Initialize a new instance from the serialized data in the file.
}
}
Another option is to provide a static factory method:
class Car {
public static Car Open(String fileName) {
var car = new Car();
// Initialize the new instance from the serialized data in the file.
return car;
}
}
The main point is that the "Open" method is not a method on a Car instance. It should either be a constructor or a static method. Then you don't have to "internally set an object equal to a reference" (which isn't possible anyway).
In some ways the line of thought you have presented in your question is similar to Prototype-based programming. However, C# is a class-based language as opposed to a prototype-based language.
There's already a method for assigning a reference to another object. It's called operator=, and is implemented as = in the language, like you write in your question:
car1 = car2
Jon Skeet explains beautifully the difference between references and objects themselves. I think that you may have a lacking understanding of the difference between objects and references to objects, but I might be wrong. If you tell us what you are trying to do and why, we could probably guide you in a better way :)
Update based on your comments:
I would suggest creating a static factory method on the Car class, something like this:
class Car {
public static Car Open(string fileName) {
return (Car) binaryFormatter.DeSerialize(File.Open(fileName));
}
And then you could say:
Car car = new Car();
car.Save(fileName);
car = Car.Open(fileName) // re-reads the car from file
"What I want to do is add an "open" function where it sets the object equal to the class it reads from the file I wrote to with the save function earlier."
You could make Open() a static function of class Car and have it return a New instance that represents the opened file: Car c = Car.Open("somefile.txt"); with code like this:
public class Car
{
// ... bunch of members for Car ...
public static Car Open(string FileName)
{
Car c = new Car();
// ... open the file and populate "c" ...
return c;
}
}
Another option is to pass the filename to the Constructor of Car and it will populate from there. You'd need some kind of "valid" field in Car, though, to indicate whether the opening of the file was successful or not.
