CMFormatDescriptionGetExtension(_:extensionKey:)
Returns an extension from the format description by using an extension key.
Declaration
func CMFormatDescriptionGetExtension(_ desc: CMFormatDescription, extensionKey: CFString) -> CFPropertyList?Parameters
- desc:
The
CMFormatDescriptionto examine. - extensionKey:
The key of the extension to return. May not be
NULL.
Return Value
An extension, or NULL if it doesn’t exist.
Discussion
The extension is always a valid property list object. This means that it will be either a CFNumber, CFString, CFBoolean, CFArray, CFDictionary, CFDate, or CFData. If it’s a CFDictionary, the keys will all be CFStrings. The extension this function returns is not retained by this call, so it’s only valid as long as the CMFormatDescription is valid — retain it to keep it longer.