XRPtr<Interface> (Compact 2013)
3/28/2014
An XRPtr<Interface> object encapsulates a COM interface pointer to a XAML for Windows Embedded object and is called a smart pointer. The template class manages resource allocation and deallocation through function calls to the IUnknown methods: QueryInterface, AddRef, and Release.
Syntax
template<typename Interface> class XRPtr
Methods
Method |
Description |
|---|---|
Calls the AddRef method of IUnknown on the encapsulated interface pointer. |
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Encapsulates a raw interface pointer in this smart pointer's type. |
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Extracts and returns the encapsulated interface pointer, and relinquishes ownership so that the returned interface will not be released by this smart pointer. |
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Calls the Release method of IUnknown on the encapsulated interface pointer. |
Operators
Operator |
Description |
|---|---|
Assigns a new value to an existing XRPtr<Interface> object. |
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Returns the address of the interface pointer contained in this class. |
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Either sets the interface pointer, copies the interface pointer and increments the reference count, or allows for the assignment of NULL to the class. |
Remarks
Smart pointers manage the reference count of an object. A smart pointer will automatically call IUnknown::Release when the smart pointer goes out of scope.
We recommend that you use smart pointers when you call methods that pass IXRDependencyObject-derived objects in XAML for Windows Embedded, instead of explicitly calling IUnknown::QueryInterface to convert a generic interface into the required object type.
All objects in XAML for Windows Embedded have smart pointer aliases declared for them. For example, to create a smart pointer instead of a raw interface pointer to IXRButton, you can create a smart pointer of type IXRButtonPtr. You can also create a smart pointer by using the template class type XRPtr<XRButton>.
The following example code creates a smart pointer by using a smart pointer alias:
IXRButtonPtr pButton;
pApplication->CreateObject(&pButton);
The following example code creates a smart pointer by using the template class:
XRPtr<XRButton> pButton;
pApplication->CreateObject(&pButton);
XRPtr<Interface> stores the return value from an API call (such as a call to IXRApplication::CreateObject), even if the return value is NULL. When you use XRPtr<Interface> with a NULL value, a debug break occurs as a warning that your code might later fail. Check the stack trace for the source of your error. Optionally, in your code, you can undefine the SHIP_BUILD preprocessor definition by using #undef (FMerge.exe) before you use #include (FMerge.exe) to include xrptr.h, and then rebuild and rerun your project. If ERRORMSG is available, debug output appears that tells you the reason for the failure.
Requirements
Header |
XRPtr.h |
sysgen |
SYSGEN_XAML_RUNTIME |