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AECoercePtrProcPtr

Defines a pointer to a function that coerces data stored in a buffer. Your pointer coercion callback routine coerces the data from the passed buffer to the specified type, returning the coerced data in a descriptor.

Declaration

typealias AECoercePtrProcPtr = (DescType, UnsafeRawPointer?, Size, DescType, SRefCon?, UnsafeMutablePointer<AEDesc>?) -> OSErr

Parameters

  • typeCode:

    The descriptor type of the original data. For a list of AppleScript’s predefined descriptor types, see 1542788 Descriptor_type_constants. See Desctype.

  • dataPtr:

    A pointer to the data to coerce.

  • dataSize:

    The length, in bytes, of the data to coerce.

  • toType:

    The desired descriptor type for the resulting descriptor. For a list of AppleScript’s predefined descriptor types, see 1542788 Descriptor_type_constants. See Desctype.

  • handlerRefcon:

    A reference constant that is stored in the coercion dispatch table entry for the handler. The Apple Event Manager passes this value to the handler each time it calls it. The reference constant may have a value of NULL.

  • result:

    A pointer to a descriptor where your coercion routine must store the descriptor that contains the coerced data. If your routine cannot coerce the data, return a null descriptor. See Aedesc.

Return Value

A result code. See Result Codes. Your handler should return noErr if it successfully handled the coercion, errAECoercionFailed if it can’t handle the coercion and it wants the Apple Event Manager to continue dispatching to other coercion handlers, or a nonzero result code otherwise.

Discussion

To provide a pointer to your coercion callback function, you create a universal procedure pointer (UPP) of type AECoercePtrUPP, using the function NewAECoercePtrUPP(_:). You can do so with code like the following:

AECoercePtrUPP MyCoercePtrUPP;
MyCoercePtrUPP = NewAECoercePtrUPP (&MyCoercePtrCallback)

You can then pass the UPP MyCoercePtrUPP as a parameter to any function that installs or removes a coercion handler, such as AEInstallCoercionHandler(_:_:_:_:_:_:). If your application installs the same coercion handler to coerce more than one type of data, you can use the same UPP to install the handler multiple times.

If you wish to call your coercion callback function directly, you can use the InvokeAECoercePtrUPP(_:_:_:_:_:_:_:) function.

After you are finished with a coercion callback function, and have removed it with the AERemoveCoercionHandler(_:_:_:_:) function, you can dispose of the UPP with the DisposeAECoercePtrUPP(_:) function. However, don’t dispose of the UPP if any remaining coercion handler uses it or if you plan to install the coercion handler again.

See Also

Callbacks