Media-class | R Documentation |
The Media
object represents a value identified by a URI. There
is a Media
subclass for each media type, such as
“text/csv” or “application/xml”. Coercion methods (see
setAs
) define mappings between Media
subclasses
and R objects. The user does not usually need to access this
functionality directly.
Each Media
subclass may be converted to/from one or more R
types. The mappings are established by setAs
.
The following bi-directional mappings are built into the package:
application/xml , text/html |
XMLAbstractNode |
application/json | list |
text/csv | data.frame |
text/* | character
|
But call mediaCoercionTable
to see what is defined in the
current session.
The as
function is the canonical interface to converting
media to R objects. It (usefully) requires that the user specify the
target R type. For convenience, the mediaTarget
generic
returns the default R type for a given Media
object.
To support a new media type, one should define a Media
subclass
with the same name as the media type (application/xml
), a
corresponding mediaTarget
method, and all relevant
coerce
methods. See the Media
class hierarchy to
determine where the new type fits.
mediaCoercionTable()
: Returns a character matrix with
columns “from” and “to”, indicating the available
coercions of media types to/from R objects.
Michael Lawrence
txt <- '{"json":{"rocks":true}}' json <- as(txt, "application/json") as(json, mediaTarget(json))
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