Need Help getting around memory pointing.

**hype261** · May 3 '10, 04:33 PM

Without seeing your logic for adding steps to a relevant instruction it is hard to say what the problem actually is. If I were trying to solve this problem I would not use List<List<List< String>>>. This makes it very difficult to see where you are actually having a problem.

I would change this to a first class concept.

class Item
{

public void addSubItem(Item item)
{
}
public void addInstruction( String instruction)
{
}
private string name;
private List<Item> items; //the subitems that need to be constructed
private List<String> instructions; //the instructions for this item
}

So the Dining Set would contain in its list of items a Table and Chair.

You would have to write your more method using this concept, but it will be clearer to see what is going on.

**MZimmerman6** · May 3 '10, 04:49 PM

Originally posted by hype261

Without seeing your logic for adding steps to a relevant instruction it is hard to say what the problem actually is. If I were trying to solve this problem I would not use List<List<List< String>>>. This makes it very difficult to see where you are actually having a problem.

I would change this to a first class concept.

class Item
{

public void addSubItem(Item item)
{
}
public void addInstruction( String instruction)
{
}
private string name;
private List<Item> items; //the subitems that need to be constructed
private List<String> instructions; //the instructions for this item
}

So the Dining Set would contain in its list of items a Table and Chair.

You would have to write your more method using this concept, but it will be clearer to see what is going on.

unfortunately I was told to use List<List<List< String>>> by the person who I amd doing this for. I am not particularly sure why, but ehh whatever.

When adding steps, I have a List like

Code:

List<String> steps = new List<String>();
List<List<String>> cases = new List<List<String>>();

steps.add("case 1: Some string");
steps.add("case 1: Some other string");

cases.add(steps);
steps.Clear();

steps.add("case 2: Some string");
steps.add("case 2: Some other string");
cases.add(steps);

I clear out the steps list because case 2 has different steps from case 1.

That is how I am working that, and the problem is that case 1 will end up having the same steps as case 2. it overwrites them or changes the reference or something. Any suggestions with that?

**hype261** · May 3 '10, 05:06 PM

Originally posted by MZimmerman6

unfortunately I was told to use List<List<List< String>>> by the person who I amd doing this for. I am not particularly sure why, but ehh whatever.

When adding steps, I have a List like

Code:

List<String> steps = new List<String>();
List<List<String>> cases = new List<List<String>>();

steps.add("case 1: Some string");
steps.add("case 1: Some other string");

cases.add(steps);
steps.Clear();

steps.add("case 2: Some string");
steps.add("case 2: Some other string");
cases.add(steps);

I clear out the steps list because case 2 has different steps from case 1.

That is how I am working that, and the problem is that case 1 will end up having the same steps as case 2. it overwrites them or changes the reference or something. Any suggestions with that?

Basically your problem is what you believed.

When you add steps to to cases on line 7 you are just doing a shallow copy on to the list. That is you are just copy the address of the steps on the heap. So any modification you do to steps from this point on will affect the one stored in cases.

To get around this you need to make every step its own object by doing
List<String> steps = new List<String>();

I would suggest rolling the addition of steps into its own method

**MZimmerman6** · May 3 '10, 05:18 PM

Originally posted by hype261

Basically your problem is what you believed.

When you add steps to to cases on line 7 you are just doing a shallow copy on to the list. That is you are just copy the address of the steps on the heap. So any modification you do to steps from this point on will affect the one stored in cases.

To get around this you need to make every step its own object by doing
List<String> steps = new List<String>();

I would suggest rolling the addition of steps into its own method

Oh it already is its own method, do not worry, I just wrote a simplified version of what I am doing because there is a lot more.

But i am unsure exactly what you mean by making each step its own object.

is there any way to make a more "deep" copy of the contents. say copy the contents rather than the reference?

**hype261** · May 3 '10, 05:46 PM

Originally posted by MZimmerman6

Oh it already is its own method, do not worry, I just wrote a simplified version of what I am doing because there is a lot more.

But i am unsure exactly what you mean by making each step its own object.

is there any way to make a more "deep" copy of the contents. say copy the contents rather than the reference?

When you do the following declaration.

Code:

List<String> steps = new List<String>();

What you are doing is creating an object of type List<String> on the heap. The variable steps just contains the address of that object that is on the heap.

So if your steps are in its own method.

Code:

public List<String> addStep()
{
  List<String> steps = new List<String>();
<----- get the data for the steps
return steps;
}

So to use this all you would have to do is

Code:

cases.add(addStep());

**MZimmerman6** · May 3 '10, 06:08 PM

Originally posted by hype261

When you do the following declaration.

Code:

List<String> steps = new List<String>();

What you are doing is creating an object of type List<String> on the heap. The variable steps just contains the address of that object that is on the heap.

So if your steps are in its own method.

Code:

public List<String> addStep()
{
  List<String> steps = new List<String>();
<----- get the data for the steps
return steps;
}

So to use this all you would have to do is

Code:

cases.add(addStep());

I had tried something very similar to that before hand thinking that a method would break the pointer issue, much to no success. I was/am still having the same issue.

**hype261** · May 3 '10, 07:04 PM

Originally posted by MZimmerman6

I had tried something very similar to that before hand thinking that a method would break the pointer issue, much to no success. I was/am still having the same issue.

Could you post the method you are using to add a step to the cases?

**tlhintoq** · May 4 '10, 01:46 AM

Since each thing is a subnode of the parent thing...
I would use a treeview and make each thing a treenode.
Your professor can live with the logic of what you are doing, so long as you make a function in the end that outputs to List<string> objects.

**MZimmerman6** · May 4 '10, 01:13 PM

Originally posted by tlhintoq

Since each thing is a subnode of the parent thing...
I would use a treeview and make each thing a treenode.
Your professor can live with the logic of what you are doing, so long as you make a function in the end that outputs to List<string> objects.

I got it working now. I ended up redoing the part where I add cases, declaring a new list each time, and it worked.

Note: Not for school, For work :]

Thanks for all of your help though!

Need Help getting around memory pointing.

Need Help getting around memory pointing.

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