IAccessible::get_accChild method (oleacc.h)

Článek
02/22/2024

The IAccessible::get_accChild method retrieves an IDispatch for the specified child, if one exists. All objects must support this property.

Syntax

HRESULT get_accChild(
  [in]          VARIANT   varChild,
  [out, retval] IDispatch **ppdispChild
);

Parameters

[in] varChild

Type: VARIANT

Identifies the child whose IDispatch interface is retrieved. For more information about initializing the VARIANT, see How Child IDs Are Used in Parameters.

[out, retval] ppdispChild

Type: IDispatch**

[out, retval] Receives the address of the child object's IDispatch interface.

Return value

Type: HRESULT

If successful, returns S_OK.

If not successful, returns one of the values in the table that follows, or another standard COM error code. Servers return these values, but clients must always check output parameters to ensure that they contain valid values. For more information, see Checking IAccessible Return Values.

Error	Description
S_FALSE	The child is not an accessible object.
E_INVALIDARG	An argument is not valid.

Remarks

Servers expose elements as either elements (child IDs) or full objects (IAccessible interface pointers). If a child is an element, get_accChild returns S_FALSE, and the parent will provide information for that child. If the child is a full object, get_accChild will return the IAccessible interface pointer and the parent will not provide information about that child. If get_accChild fails because the server application cannot create an accessible object due to a temporary system error (such as an out-of-memory error), the server should return a suitable failure code.

Note to server developers: If varChildID contains VT_EMPTY, you should return E_INVALIDARG.

Server Example

The following example code shows an implementation for an object that does not have any children, or whose children are elements rather than objects.


HRESULT STDMETHODCALLTYPE AccServer::get_accChild( 
    VARIANT varChild,
    IDispatch **ppdispChild)
{
    if (varChild.vt != VT_I4)
    {
        *ppdispChild = NULL;
        return E_INVALIDARG;
    }
    *ppdispChild = NULL;    
    return S_FALSE;     
};

Requirements

Requirement	Value
Minimum supported client	Windows 2000 Professional [desktop apps only]
Minimum supported server	Windows Server 2003 [desktop apps only]
Target Platform	Windows
Header	oleacc.h
Library	Oleacc.lib
DLL	Oleacc.dll
Redistributable	Active Accessibility 1.3 RDK on Windows NT 4.0 with SP6 and later and Windows 95

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