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ExtensionType class


The ExtensionType class inherits from DataType, but also defines extra methods specific to extension types:

  • $storage_type(): Returns the underlying DataType used to store values.

  • $storage_id(): Returns the Type identifier corresponding to the $storage_type().

  • $extension_name(): Returns the extension name.

  • $extension_metadata(): Returns the serialized version of the extension metadata as a raw() vector.

  • $extension_metadata_utf8(): Returns the serialized version of the extension metadata as a UTF-8 encoded string.

  • $WrapArray(array): Wraps a storage Array into an ExtensionArray with this extension type.

In addition, subclasses may override the following methods to customize the behaviour of extension classes.

  • $deserialize_instance(): This method is called when a new ExtensionType is initialized and is responsible for parsing and validating the serialized extension_metadata (a raw() vector) such that its contents can be inspected by fields and/or methods of the R6 ExtensionType subclass. Implementations must also check the storage_type to make sure it is compatible with the extension type.

  • $as_vector(extension_array): Convert an Array or ChunkedArray to an R vector. This method is called by as.vector() on ExtensionArray objects, when a RecordBatch containing an ExtensionArray is converted to a data.frame(), or when a ChunkedArray (e.g., a column in a Table) is converted to an R vector. The default method returns the converted storage array.

  • $ToString() Return a string representation that will be printed to the console when this type or an Array of this type is printed.