Function calls in Autodesk Inventor C++ programming

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Every COM C++ Inventor API method comes in 2 "flavors":

1.	low level methods: that take output param as input and return HRESULT, for example hRes = get_Item (Index,&Pointer).

2.	high level methods: that return the result directly and throw exceptions, for example Pointer = GetItem (Index)

A concrete example of the difference is the visibility of workaxes:

// This "low level" version will not crash and you can look at the success or not via hRes

hRes = pWorkAxis->put_Visible (vbVisib) ;

if (FAILED(hRes)) {

// Show some error message if you want

}

// This "high level" version will throw and exception and crash if something is wrong

pWorkAxis->Visible = vbVisib ;

There are other functions which are high and low distinguished by whether or not they have Method... in front of the name, high level methods are usually prefixed "Method".

Some examples :

HRESULT hRes = pWorkPlanesList->get_Item (CComVariant(1),&pWorkPlane) ; // low level version

WorkPlanePtr pWorkPlane = pWorkPlanesList->GetItem (CComVariant(1)) ; // high level version

...and...

HRESULT hRes = pConstraintList->AddAngleConstraint (...etc...,&pAngConstraint) ; // low level version

AngleConstraintPtr pAngConstraint = pConstraintList->MethodAddAngleConstraint(...etc...) ; // high level version

Note that with "low level" versions you often pass the address of a pointer which is the "return value" of the function.