Hi there,

I have a function which is to Enumerate Project Tasks. Each Task goes into it's own __gc class, and therefore is in a class array. With unmanaged C++ it is easy to change the data a pointer points to. However, this managed C++ seems to garbage collect when the original pointer leaves the scope.

I am using /oldSyntax line.

Here is some brief code of my function. Please note that CSchedTask is __gc class CSchedTask.

int EnumScheduleTasks(String *ProjectID, CSchedTask *Tasks[])

{

MyDataset *dsTasks = new MyDataset();

//... more code is here which defines iTasks, int iTasks = ...;

//Initialize array.

CSchedTask __pin *cTasks[] = new CSchedTask*[iTasks];

for(int i=0;i<iTasks;i++)

cTasks = new CSchedTask();

//Enumerate tasks.

strQuery = S"SELECT * FROM HS_ProjectTask WHERE ProjectID = '";

cstrcat(&strQuery, ProjectID);

cstrcat(&strQuery, S"' AND ProjectElementID Is NULL ORDER BY Sequence");

dsTasks->SQLText = strQuery;

//Populate cTasks class array with Tasks values.

for(int i=0;i<iTasks;i++)

{

cTasks->ProjectTaskID = dsTasks->ReadString(S"ProjectTaskID");

cTasks->ProjectComponentID = dsTasks->ReadString(S"ProjectComponentID");

cTasks->IsDetailedSchedule = dsTasks->ReadShort("IsDetailedSchedule");

cTasks->IsComplete = dsTasks->ReadShort("IsComplete");

cTasks->IsStartDateFixed = dsTasks->ReadShort("IsStartDateFixed");

cTasks->Duration = Convert::ToUInt32(dsTasks->ReadString(S"Duration"));

cTasks->StartDate = dsTasks->ReadDateTime("StartDate");

cTasks->EndDate = dsTasks->ReadDateTime("EndDate");

dsTasks->MoveNext();

}

//Tasks array now is equal to cTasks array. After this function ends, the array Tasks points to is <undefined value>

Tasks = cTasks;

return iTasks;

}

---

The calling code is below:

CSchedTask *cTask[];

int iTasks = EnumScheduleTasks(S"C7D2D63F2FD84C18AD9EB9BBF66D585E", cTask);

 

At this point cTask is undefined and contains no data.

Any help is greatly appreciated. I'm likely missing something incredibly simple.

This has nothing to do with garbage collection. The same thing will happen in native C++ when you pass an array (or pointer) to a function. You can change the contents of the array but you cannot change the array (pointer). You need a pointer to pointer paramter to do that:

int EnumScheduleTasks(String *ProjectID, CSchedTask* (*Tasks)[])

{

... your code

*Tasks = cTasks; // set the new array

return iTasks;

}

The calling code is below:

CSchedTask *cTask[];

int iTasks = EnumScheduleTasks(S"C7D2D63F2FD84C18AD9EB9BBF66D585E", &cTask); // pass the address of cTask

Hello Mike,

Thankyou for your timely reply. This has helped me greatly.

-Ryan