Documentation

Passing Data to COM Objects

When you use a COM object in a MATLAB^® command, the MATLAB types you pass in the call are converted to types native to the COM object. MATLAB performs this conversion on each argument that is passed. This section describes the conversion.

MATLAB converts MATLAB arguments into types that best represent the data to the COM object. The following table shows all the MATLAB base types for passed arguments and the COM types defined for input arguments. Each row shows a MATLAB type followed by the possible COM argument matches. For a description of COM variant types, see the table in Handling Data from COM Objects.

Handling Data from COM Objects

Data returned from a COM object is often incompatible with MATLAB types. When this occurs, MATLAB converts the returned value to a data type native to the MATLAB language. This section describes the conversion performed on the various types that can be returned from COM objects.

The following table shows how MATLAB converts data from a COM object into MATLAB variables.

Unsupported Types

MATLAB does not support the following COM interface types and displays the warning ActiveX - unsupported VARIANT type encountered.

Passing MATLAB Data to ActiveX Objects

The tables also show the mapping of MATLAB types to COM types that you must use to pass data from MATLAB to an Microsoft^® ActiveX^® object. For all other types, MATLAB displays the warning ActiveX - invalid argument type or value.

Passing MATLAB SAFEARRAY to COM Object

The SAFEARRAY data type is a standard way to pass arrays between COM objects. This section explains how MATLAB passes SAFEARRAY data to a COM object.

• Default Behavior in MATLAB Software

• Examples

• How to Pass a Single-Dimension SAFEARRAY

• Passing SAFEARRAY by Reference

B = [2 3 4]
B =
     2     3     4

No. of dimensions: 2
Dim: 1, 	 No. of elements: 1 
Dim: 2, 	 No. of elements: 3 
	 	 Elements: 
	 	 2.0 
	 	 3.0 
	 	 4.0

C = [1;2;3]
C =
     1
     2
     3

No. of dimensions: 2
Dim: 1, 	 No. of elements: 3 
Dim: 2, 	 No. of elements: 1 
Elements: 
	 	 1.0 
	 	 2.0 
	 	 3.0

D = [2 3 4 5;5 6 7 8]

D =
     2     3     4     5
     5     6     7     8

No. of dimensions: 2
Dim: 1, 	 No. of elements: 2 
Dim: 2, 	 No. of elements: 4 
Elements: 
	 	 2.0 
	 	 3.0 
	 	 4.0 
	 	 5.0 
	 	 5.0 
	 	 6.0 
	 	 7.0 
	 	 8.0

Reading SAFEARRAY from COM Objects in MATLAB Applications

This section explains how MATLAB reads SAFEARRAY data from a COM object.

MATLAB reads a one-dimensional SAFEARRAY with n elements from a COM object as a 1-by-n matrix. For example, using methods from the MATLAB sample control mwsamp, type:

h=actxcontrol('mwsamp.mwsampctrl.1')
a = GetI4Vector(h)

MATLAB displays:

a =
           1           2           3

MATLAB reads a two-dimensional SAFEARRAY with n elements as a 2-by-n matrix. For example:

a = GetR8Array(h)

MATLAB displays:

a =
     1     2     3
     4     5     6

MATLAB reads a three-dimensional SAFEARRAY with two elements as a 2-by-2-by-2 cell array. For example:

a = GetBSTRArray(h)

MATLAB displays:

a(:,:,1) = 

    '1 1 1'    '1 2 1'
    '2 1 1'    '2 2 1'

a(:,:,2) = 

    '1 1 2'    '1 2 2'
    '2 1 2'    '2 2 2'

Displaying MATLAB Syntax for COM Objects

To determine which MATLAB types to use when passing arguments to COM objects, use the invoke or methodsview functions. These functions list all the methods found in an object, along with a specification of the types required for each argument.

Consider a server called MyApp, which has a single method TestMeth1 with the following syntax:

HRESULT TestMeth1 ([out, retval] double* dret);

This method has no input argument, and it returns a variable of type double. The following pseudo-code displays the MATLAB syntax for calling the method.

h = actxserver('MyApp');
invoke(h)

MATLAB displays:

ans = 
   TestMeth1 = double TestMeth1 (handle)

The signature of TestMeth1 is:

double TestMeth1(handle)

MATLAB requires you to use an object handle as an input argument for every method, in addition to any input arguments required by the method itself.

Use one of the following pseudo-code commands to create the variable var, which is of type double.

var = h.TestMeth1;

or:

var = TestMeth1(h);

Although the following syntax is correct, its use is discouraged:

var = invoke(h,'TestMeth1');

Now consider the server called MyApp1 with the following methods:

HRESULT TestMeth1 ([out, retval] double* dret);
HRESULT TestMeth2 ([in] double* d, [out, retval] double* dret);
HRESULT TestMeth3 ([out] BSTR* sout,
                   [in, out] double* dinout,
                   [in, out] BSTR* sinout,
                   [in] short sh,
                   [out] long* ln,
                   [in, out] float* b1,
                   [out, retval] double* dret);

Using the invoke function, MATLAB displays the list of methods:

ans = 
   TestMeth1 = double TestMeth1 (handle)
   TestMeth2 = double TestMeth2 (handle, double)
   TestMeth3 = [double, string, double, string, int32, single] ...
               TestMeth3(handle, double, string, int16, single)

TestMeth2 requires an input argument d of type double, and returns a variable dret of type double. Some pseudo-code examples of calling TestMeth2 are:

var = h.TestMeth2(5);

or:

var = TestMeth2(h, 5);

TestMeth3 requires multiple input arguments, as indicated within the parentheses on the right side of the equal sign, and returns multiple output arguments, as indicated within the brackets on the left side of the equal sign.

[double, string, double, string, int32, single]  %output arguments
TestMeth3(handle, double, string, int16, single) %input arguments

The first input argument is the required handle, followed by four input arguments.

TestMeth3(handle, in1, in2, in3, in4)

The first output argument is the return value retval, followed by five output arguments.

[retval, out1, out2, out3, out4, out5]

This is how the arguments map into a MATLAB command:

[dret, sout, dinout, sinout, ln, b1] = TestMeth3(handle, ...
                                       dinout, sinout, sh, b1)

where dret is double, sout is string, dinout is double and is both an input and an output argument, sinout is string (input and output argument), ln is int32, b1 is single (input and output argument), handle is the handle to the object, and sh is int16.