Getting Information about UNO Objects
The Basic RTL retrieves information about UNO objects. There are functions to evaluate objects during runtime and object properties used to inspect objects during debugging.
Checking for interfaces during runtime
Although Basic does not support the queryInterface concept like C++ and Java, it can be useful to know if a certain interface is supported by a UNO Basic object or not. The function
HasUnoInterfaces() detects this.
The first parameter
HasUnoInterfaces() expects is the object that should be tested. Parameter(s) of one or more fully qualified interface names can be passed to the function next. The function returns
True if all these interfaces are supported by the object, otherwise
Sub Main Dim oSimpleFileAccess oSimpleFileAccess = CreateUnoService( "com.sun.star.ucb.SimpleFileAccess" ) Dim bSuccess Dim IfaceName1$, IfaceName2$, IfaceName3$ IfaceName1$ = "com.sun.star.uno.XInterface" IfaceName2$ = "com.sun.star.ucb.XSimpleFileAccess2" IfaceName3$ = "com.sun.star.container.XPropertySet" bSuccess = HasUnoInterfaces( oSimpleFileAccess, IfaceName1$ ) MsgBox bSuccess ' Displays True because XInterface is supported bSuccess = HasUnoInterfaces( oSimpleFileAccess, IfaceName1$, IfaceName2$ ) MsgBox bSuccess ' Displays True because XInterface ' and XSimpleFileAccess2 are supported bSuccess = HasUnoInterfaces( oSimpleFileAccess, IfaceName3$ ) MsgBox bSuccess ' Displays False because XPropertySet is NOT supported bSuccess = HasUnoInterfaces( oSimpleFileAccess, IfaceName1$, IfaceName2$, IfaceName3$ ) MsgBox bSuccess ' Displays False because XPropertySet is NOT supported End Sub
Testing if an object is a struct during runtime
As described in the section Mapping of Structs above, structs are handled differently from objects, because they are treated as values. Use the
IsUnoStruct() function to check it the UNO Basic object represents an object or a struct. This function expects one parameter and returns
True if this parameter is a UNO struct, otherwise
Sub Main Dim bIsStruct ' Instantiate a service Dim oSimpleFileAccess oSimpleFileAccess = CreateUnoService( "com.sun.star.ucb.SimpleFileAccess" ) bIsStruct = IsUnoStruct( oSimpleFileAccess ) MsgBox bIsStruct ' Displays False because oSimpleFileAccess is NO struct ' Instantiate a Property struct Dim aProperty As New com.sun.star.beans.Property bIsStruct = IsUnoStruct( aProperty ) MsgBox bIsStruct ' Displays True because aProperty is a struct bIsStruct = IsUnoStruct( 42 ) MsgBox bIsStruct ' Displays False because 42 is NO struct End Sub
Testing objects for identity during runtime
To find out if two UNO OpenOffice.org Basic objects refer to the same UNO object instance, use the function
EqualUnoObjects(). Basic is not able to apply the comparison operator = to arguments of type object, for example,
If Obj1 = Obj2 Then will produce a runtime error.
Sub Main Dim bIdentical Dim oSimpleFileAccess, oSimpleFileAccess2, oSimpleFileAccess3 ' Instantiate a service oSimpleFileAccess = CreateUnoService( "com.sun.star.ucb.SimpleFileAccess" ) oSimpleFileAccess2 = oSimpleFileAccess ' Copy the object reference bIdentical = EqualUnoObjects( oSimpleFileAccess, oSimpleFileAccess2 ) MsgBox bIdentical ' Displays True because the objects are identical ' Instantiate the service a second time oSimpleFileAccess3 = CreateUnoService( "com.sun.star.ucb.SimpleFileAccess" ) bIdentical = EqualUnoObjects( oSimpleFileAccess, oSimpleFileAccess3 ) MsgBox bIdentical ' Displays False, oSimpleFileAccess3 is another instance bIdentical = EqualUnoObjects( oSimpleFileAccess, 42 ) MsgBox bIdentical ' Displays False, 42 is not even an object ' Instantiate a Property struct Dim aProperty As New com.sun.star.beans.Property Dim aProperty2 aProperty2 = aProperty ' Copy the struct bIdentical = EqualUnoObjects( aProperty, aProperty2 ) MsgBox bIdentical ' Displays False because structs are values ' and so aProperty2 is a copy of aProperty End Sub
Basic hides interfaces behind OpenOffice.org Basic objects that could lead to problems when developers are using API structures. It can be difficult to understand the API reference and find the correct method of accessing an object to reach a certain goal.
To assist during development and debugging, every UNO object in OpenOffice.org Basic has special properties that provide information about the object structure. These properties are all prefixed with
Dbg_ to emphasize their use for development and debugging purposes. The type of these properties is
String. To display the properties use the
Inspecting interfaces during debugging
Dbg_SupportedInterfaces lists all interfaces supported by the object. In the following example, the object returned by the function
GetProcessServiceManager() described in the previous section is taken as an example object.
oServiceManager = GetProcessServiceManager() MsgBox oServiceManager.Dbg_SupportedInterfaces
This call displays a message box:
The list contains all interfaces supported by the object. For interfaces that are derived from other interfaces, the super interfaces are indented as shown above for com.sun.star.container.XSet, which is derived from com.sun.star.container.XEnumerationAccess based upon com.sun.star.container.XElementAccess.
|If the text "(ERROR: Not really supported!)" is printed behind an interface name, the implementation of the object usually has a bug, because the object pretends to support this interface (per com.sun.star.lang.XTypeProvider, but a query for it fails. For details, see UNO Reflection API).|
Inspecting properties during debugging
Dbg_Properties lists all properties supported by the object through com.sun.star.beans.XPropertySet and through get and set methods that could be mapped to Basic object properties:
oServiceManager = GetProcessServiceManager() MsgBox oServiceManager.Dbg_Properties
This code produces a message box like the following example:
Inspecting Methods During Debugging
Dbg_Methods lists all methods supported by an object. Example:
oServiceManager = GetProcessServiceManager() MsgBox oServiceManager.Dbg_Methods
This code displays:
The notations used in
Dbg_Methods refer to internal implementation type names in Basic. The
Sbx prefix can be ignored. The remaining names correspond with the normal Basic type notation. The
SbxEMPTY is the same type as
Variant. Additional information about Basic types is available in the next chapter.
|Basic uses the com.sun.star.lang.XTypeProvider interface to detect which interfaces an object supports. Therefore, it is important to support this interface when implementing a component that should be accessible from Basic. For details, see Writing UNO Components.|
The list of elements may be inconveniently long for MsgBox display. Code is available to write all Dbg_ elements to a new Writer document. See OpenOffice.org Macros > Tools > Debug > WritedbgInfo. The Tools library must be loaded to use this routine:
GlobalScope.BasicLibraries.LoadLibrary( "Tools" ) Call Tools.WritedbgInfo(MyObject)
|Content on this page is licensed under the Public Documentation License (PDL).|