Message-class: Class "Message"

Description

R representation of protocol buffer messages. This is a thin wrapper around the Message c++ class that holds the actual message as an external pointer.

Arguments

Objects from the Class

Objects are typically created by the new function invoked on a Descriptor object.

Slots

pointer:: external pointer to the c++ Message object
type:: fully qualified name of the message type

Methods

as.character: signature(x = "Message"): returns the debug string of the message. This is built from a call to the DebugString message of the Message object
toString: signature(x = "Message"): same as as.character
$<-: signature(x = "Message"): set the value of a field of the message.
$: signature(x = "Message"): gets the value of a field. Primitive types are brough back to R as R objects of the closest matching R type. Messages are brought back as instances of the Message class.
[[: signature(x = "Message"): extracts a field identified by its name or declared tag number
[[<-: signature(x = "Message"): replace the value of a field identified by its name or declared tag number
serialize: signature(object = "Message"): serialize a message. If the "connection" argument is NULL, the payload of the message is returned as a raw vector, if the "connection" argument is a binary writable connection, the payload is written into the connection. If "connection" is a character vector, the message is sent to the file (in binary format).
show: signature(object = "Message"): displays a short text about the message
update: signature(object = "Message"): set several fields of the message at once
length: signature(x = "Message"): The number of fields actually contained in the message. A field counts in these two situations: the field is repeated and the field size is greater than 0, the field is not repeated and the message has the field.
setExtension: signature(object = "Message"): set an extension field of the Message.
getExtension: signature(object = "Message"): get the value of an extension field of the Message.
str: signature(object = "Message"): displays the structure of the message
identical: signature(x = "Message", y = "Message"): Test if two messages are exactly identical
==: signature(e1 = "Message", e2 = "Message"): Same as identical
!=: signature(e1 = "Message", e2 = "Message"): Negation of identical
all.equal: signature(e1 = "Message", e2 = "Message"): Test near equality
names: signature(x = "Message"): extracts the names of the message.

References

The Message class from the C++ proto library. http://code.google.com/apis/protocolbuffers/docs/reference/cpp/google.protobuf.message.html

Examples

Run this code

## Not run: 
# # example proto file supplied with this package
# proto.file <- system.file( "proto", "addressbook.proto", package = "RProtoBuf" ) 
# 
# # reading a proto file and creating the descriptor
# Person <- P( "tutorial.Person", file = proto.file )
# ## End(Not run)


PhoneNumber <- P( "tutorial.Person.PhoneNumber" )

# creating a prototype message from the descriptor
p <- new( Person )
p$email # not set, returns default value
p$id    # not set, returns default value
as.character( p ) # empty
has( p, "email" ) # is the "email" field set
has( p, "phone" ) # is the "email" field set
length( p )       # number of fields actually set

# update several fields at once
romain <- update( new( Person ), 
	email = "francoisromain@free.fr", 
	id = 1, 
	name = "Romain Francois", 
	phone = new( PhoneNumber , number = "+33(0)...", type = "MOBILE" )
	)

# supply parameters to the constructor
dirk <- new( Person, 
	email = "edd@debian.org", 
	id = 2, 
	name = "Dirk Eddelbuettel" ) 
# update the phone repeated field with a list of PhoneNumber messages
dirk$phone <- list( 
	new( PhoneNumber , number = "+01...", type = "MOBILE" ), 
	new( PhoneNumber , number = "+01...", type = "HOME" ) )
	
# with/within style
saptarshi <- within( new(Person), {
	id <- 3
	name <- "Saptarshi Guha"
	email <- "saptarshi.guha@gmail.com" 
} )

# make an addressbook
book <- new( tutorial.AddressBook, person = list( romain, dirk, saptarshi ) )

# serialize the message to a file
tf <- tempfile( )
serialize( book, tf )

# the payload of the message
serialize( book, NULL )

# read the file into a new message
m <- tutorial.AddressBook$read( tf )
writeLines( as.character( m ) )
sapply( m$person, function(p) p$name )

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