objectAsJSON: Construct a String in JSON Notation to Represent an R Object

In XR: A Structure for Interfaces from R

Description

The XR structure requires a server-language function objectFromJSON() which parses an object description in JSON. Methods for generic function objectAsJSON() should produce the appropriate string.

Usage

objectAsJSON(object, prototype = prototypeObject(), level = 1)

## S4 method for signature 'array'
objectAsJSON(object, prototype = prototypeObject(),
  level = 1)

## S4 method for signature 'environment'
objectAsJSON(object, prototype = prototypeObject(),
  level = 1)

## S4 method for signature 'list'
objectAsJSON(object, prototype = prototypeObject(),
  level = 1)

## S4 method for signature 'envRefClass'
objectAsJSON(object, prototype = prototypeObject(),
  level = 1)

## S4 method for signature 'Interface'
objectAsJSON(object, prototype = prototypeObject(),
  level = 1)

## S4 method for signature 'AssignedProxy'
objectAsJSON(object, prototype = prototypeObject(),
  level = 1)

## S4 method for signature 'ProxyClassObject'
objectAsJSON(object,
  prototype = prototypeObject(), level = 1)

Arguments

object	The object to be converted.
prototype	The prototype server class; see asServerObject.
level	Will be 1 for top-level call, incremented when recalled for an element. Used to make choices about scalars.

Details

This function is typically called from a method for asServerObject. Methods for objectAsJSON() in turn often call one or both of two helper functions: asJSONS4(), which produces the full description of the R object; and typeToJSON(), which produces the code for the basic R types, ignoring all class or attribute information.

Value

A string that will be parsed according to JSON grammar.

Methods (by class)

• array: treat matrix and array objects as legitimate S3 objects

• environment: An environment is encoded with its class, in contrast to a named list which may be a simple dictionary.

• list: A list will be encoded as a JSON list if it has no names, as a JSON dictionary if it has all distinct, non-empty names, or with an explicit representation in all other cases.

• envRefClass: An explicit representation that includes the fields.

• Interface: An interface object is transmitted via its character string Id, enough to identify the object; the rest is too R-dependent to be useful.

• AssignedProxy: Gets the object back from the server, then recalls the generic. It's usually not a good idea to get here, because bringing the proxy back and then converting it again is not foolproof; better to make direct use of the proxy. But if a proxy object is part of an ordinary list, environment or other R object, this method will be used.

• ProxyClassObject: Gets the object back from the server, then recalls the generic. See the comments under the "AssignedProxy" method.

References

Chambers, John M. (2016) Extending R, Chapman & Hall/CRC. ( Chapter 13, discussing this package, is included in the package: ../doc/Chapter_XR.pdf.)

XR documentation built on May 2, 2019, 6:01 a.m.