topic Can not connvert int to AcDbObjectIdArray error when NULL is assign to AcDbObjectIdArray variable in ObjectARX 2023. in ObjectARX Forum

Can not connvert int to AcDbObjectIdArray error when NULL is assign to AcDbObjectIdArray variable in ObjectARX 2023.

nkokate052 — Wed, 21 Sep 2022 12:10:13 GMT

Please resolve this issue.

If I assign NULL to AcDbObjectIdArray variable in ObjectARX 2023 in visual studio 2019 it is giving error can not convert from int to AcDbObjectIdArray. Screen shot is attached with this.

Example :

AcDbObjectIdArray arrObj = NULL;

this giving error can not convert from int to AcDbObjectIdArray.

Re: Can not connvert int to AcDbObjectIdArray error when NULL is assign to AcDbObjectIdArray variable in ObjectARX 2023.

tbrammer — Wed, 21 Sep 2022 12:48:14 GMT

Just write AcDbObjectIdArray arrObj; to get an empty array.

Re: Can not connvert int to AcDbObjectIdArray error when NULL is assign to AcDbObjectIdArray variable in ObjectARX 2023.

nkokate052 — Wed, 21 Sep 2022 12:59:59 GMT

but i have to set default value to AcDbObjectIdArray variable in function declaration.

What can I do to set default value?

Re: Can not connvert int to AcDbObjectIdArray error when NULL is assign to AcDbObjectIdArray variable in ObjectARX 2023.

tbrammer — Wed, 21 Sep 2022 14:22:00 GMT

AcDbObjectIdArray has a very nice default constructor that creates an empty array of AcDbObjectIds. You just don't need a default value. If you insist in assigning a default value (i.e. for syntactical reasons) you can do something like this:

AcDbObjectIdArray emptyIdArray; // global variable void fkt() { AcDbObjectIdArray ids1 = emptyIdArray; AcDbObjectIdArray ids2 = AcDbObjectIdArray(); }

AcDbObjectIdArray is a typedef:

typedef AcArray<AcDbObjectId> AcDbObjectIdArray;

The assignment operator of AcArray<T,R> only accepts another AcArray:

AcArray<T,R>& operator = (const AcArray<T,R>&); AcArray<T,R>& operator = (AcArray<T,R>&&);

Re: Can not connvert int to AcDbObjectIdArray error when NULL is assign to AcDbObjectIdArray variable in ObjectARX 2023.

autodaug — Wed, 21 Sep 2022 22:22:53 GMT

@nkokate052 wrote:

but i have to set default value to AcDbObjectIdArray variable in function declaration.

What can I do to set default value?

It sounds like you might be passing the array by value, as in: myfunc(AcDbObjectIdArray idArr)

That's not usually the best practice, because it can cause unnecessary copying of the array during func calls.

If the array is not being modified, you can pass a const ref, as in: myfunc(const AcDbObjectIdArray & idArr)

And if it *is* being modified, then pass it as a non-const ref: myfunc(AcDbObjectIdArray & idArr)

Or, if the array arg is optional, you can make it a ptr : myfunc(const AcDbObjectIdArray *pArr = nullptr);

Re: Can not connvert int to AcDbObjectIdArray error when NULL is assign to AcDbObjectIdArray variable in ObjectARX 2023.

daniel_cadext — Thu, 22 Sep 2022 01:02:34 GMT

looks like you're trying to do an optional argument, you can pass by pointer.

static void Foo() { AcDbObjectIdArray ids; func(10, &ids); acutPrintf(_T("\nfoo %ld"), ids.length()); } static void Far() { AcDbObjectIdArray ids; func(10); acutPrintf(_T("\nfar = %ld"), ids.length()); } static void foobar() { std::unique_ptr<AcDbObjectIdArray> pids; //is null func(10, pids.get()); if (pids) acutPrintf(_T("\nfoobar = %ld"), pids->length()); else acutPrintf(_T("\nfoobar = %ld"), 0); } static void furbar() { std::unique_ptr<AcDbObjectIdArray> pids(new AcDbObjectIdArray()); func(10, pids.get()); if (pids) acutPrintf(_T("\nfurbar = %ld"), pids->length()); else acutPrintf(_T("\nfurbar = %ld"), 0); } static void func(size_t cnt, AcDbObjectIdArray* ids = nullptr) { if (ids != nullptr) { for (size_t idx = 0; idx < cnt; idx++) ids->append(AcDbObjectId::kNull); } }

Re: Can not connvert int to AcDbObjectIdArray error when NULL is assign to AcDbObjectIdArray variable in ObjectARX 2023.

tbrammer — Thu, 22 Sep 2022 07:11:17 GMT

As I suggested before you can pass a default value to a function like this:

int defArr(AcDbObjectIdArray arr = AcDbObjectIdArray());

or like this:

//Header file: extern AcDbObjectIdArray defaultIdArray; // global variable int defArr2(AcDbObjectIdArray arr=defaultIdArray); //CPP file: AcDbObjectIdArray defaultIdArray; int defArr2(AcDbObjectIdArray arr) { return arr.length(); //i.e. }

@autodaug's approach is a little more efficient.

But if you don't want to change function signatures you can do it like this.

Re: Can not connvert int to AcDbObjectIdArray error when NULL is assign to AcDbObjectIdArray variable in ObjectARX 2023.

autodaug — Thu, 22 Sep 2022 16:09:05 GMT

I agree, if you want to pass the array by value, and have a default parameter, then it should be = AcDbObjectIdArray()

The second approach with the global defaultIdArray object is more complicated and less flexible, imo.

Re: Can not connvert int to AcDbObjectIdArray error when NULL is assign to AcDbObjectIdArray variable in ObjectARX 2023.

daniel_cadext — Thu, 22 Sep 2022 22:41:36 GMT

I assumed it was an [in][out] parameter, with a global or a new there's no way to know since there's no null.