C++ - map<int, object> Dictionary object with reference problem

Question

C++ - map<int, object> Dictionary object with reference problem

Markus Freitag 3,791

Hello,

I have two maps. Please look there ///******** change is not inside the first map.

map<int, CInfos> DicIndexInfos;
map<int, CInfos> DicIndexInfosCurrentPanel;



infos.ProductID = infos.ProductID.Trim();
infos.MaterialSN = infos.MaterialSN.Trim();
infos.AssemblySN = infos.AssemblySN.Trim();
infos.State = infos.State.Trim();

DicIndexInfos[index] = infos;

if (infos.State.MakeLower() != "used" && isCurrentPanelFilled == false)
{
    // *** Fill current panel
    counterIndexCurrentPanel++;
    infos.State = "used";    ///******** change is not inside the first map.

    DicIndexInfosCurrentPanel[counterIndexCurrentPanel] = infos;

How I can solve this?

When I change something, the first map does not have the changed state. How do I do this as a reference?
In C# I know this differently.

Thanks.

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Answer 1

Guido Franzke 2,191

Hello,
you could use infos as a reference variable in your first map, e.g.:

CInfos& infos = DicIndexInfos[index];

 infos.ProductID = infos.ProductID.Trim();
 infos.MaterialSN = infos.MaterialSN.Trim();
 infos.AssemblySN = infos.AssemblySN.Trim();
 infos.State = infos.State.Trim();

 if (infos.State.MakeLower() != "used" && isCurrentPanelFilled == false)
 {
     // *** Fill current panel
     counterIndexCurrentPanel++;
     infos.State = "used";

Regards, Guido

Edit: have a look at this post: is-it-safe-to-get-an-object-in-stdmap-by-reference

Guido Franzke 2,191 Reputation points

2022-03-16T12:50:02.067+00:00

By the way, regarding Trim(): What are the types of the members?
The member "State" looks like a CString, so Trim() would be the CString-function.
Then you don't need infos.State = infos.State.Trim();
You can only write : infos.State.Trim();
The CString-Trim() will trim the State variable.

Markus Freitag 3,791

OK thanks.

You read the current object inside the map as reference, then you change it. Right?

infos.AssemblySN = infos.AssemblySN.Trim();

// is the same

infos.AssemblySN.Trim();
//
//right? I do not need the return value.

Guido Franzke 2,191 Reputation points

2022-03-16T13:28:37.547+00:00
Yes.

If you only want the variable "infos" to reference the object in the first map, you can use the reference as I showed you.

You don't need the return value of Trim for CString - the string is already trimmed, you don't need the assignment to the same string: cstringt-class
Markus Freitag 3,791 Reputation points

2022-03-16T17:25:43.977+00:00

Thanks for your help!

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C++ - map<int, object> Dictionary object with reference problem

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