Overwriting an object

Question

I have a situation where I get a reference to an object that I would like to "overwrite" with another object of the same type. I know by design that the objects are of the same type. I do not have access to the parent object in this function.

The dataobject is defines as like:

    Class DataObject
    {
         public List<int> Stuff = new List<int>();
    }

Then there is a method

    void DoStuff(object obj)
    {
         // At this point I know that obj is List<int>
         // Create new object from some source
         var newList = new List<int>();

         // Here I would like to make the passed object the new object
         (the pointer of obj) = (the pointer of newlist)
    }

I don't know if this is possible. It's just something I've been banging my head against for a couple of hours now and my brain seems to have stopped working.

Thanks in advance

Johan

You are not acttly just trying to replace the contents of Stuff are you? eg `void DoStuff() { this.Stuff = new List; } — Bob Vale, Jul 08 '11 at 10:38

score 0 · Answer 1 · edited May 23 '17 at 11:55

0

You could use the Clone function but take a look at the following Stackoverflow link that has a nice method for cloning objects.

edited May 23 '17 at 11:55

Community

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answered Jul 08 '11 at 10:34

Jethro

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score 0 · Accepted Answer · answered Jul 08 '11 at 10:34

0

Pass object by reference:

void DoStuff(ref DataObject dataObject)
{
    dataObject = ...;
}

ref object won't be allowed here, however.

answered Jul 08 '11 at 10:34

Anton Gogolev

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score 0 · Answer 3 · answered Jul 08 '11 at 10:34

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No, it's not possible with your current code - the reference is passed by value, and is thus entirely independent of how you originally accessed it. Even if you changed obj to be a ref parameter, you wouldn't be able to call the method with ref Stuff because the types would be incorrect. You could potentially do it with a generic parameter:

void DoStuff<T>(ref T obj)
{
    object newList = new List<int>();
    obj = (T) newList;
}

That's pretty horrible though.

It's normally a design smell to want to do this - if you can explain more about the bigger picture, we may be able to help more.

answered Jul 08 '11 at 10:34

Jon Skeet

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I have a Command object model that allows for piping commands together. A command is of type CommandBase where the T:s are the model. I use delegates to pipe commands to different parts of the model if the signatures of the commands doesn't match. That is if A -> B with data A.Outdata.List -> B.Indata I map them using CommandA.PipeResultTo().MapInput(e=>e.Outdata.List). At the point of writing that statement, e.Outdata is null since the previous command hasn't been executed yet. – Johan Karlsson Jul 08 '11 at 10:52

score 0 · Answer 4 · answered Jul 08 '11 at 10:36

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obj = newList what difference it will make if pointer of obj is changed to newList or pointer of newList will be changed to obj?

answered Jul 08 '11 at 10:36

hungryMind

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Because obj is a member of the main DTO. If you do the above the main object will still reference to old one and obj will just be a reference to the new one. – Johan Karlsson Jul 08 '11 at 10:53

Overwriting an object

4 Answers4