R: Simple classes for identifying an XML document containing R...

XMLCodeFile-class {XML} | R Documentation

## Simple classes for identifying an XML document containing R code

### Description

These two classes allow the user to identify an XML document or file as containing R code (amongst other content). Objects of either of these classes can then be passed to `source` to read the code into R and also used in `link{xmlSource}` to read just parts of it. `XMLCodeFile` represents the file by its name; `XMLCodeDoc` parses the contents of the file when the R object is created. Therefore, an `XMLCodeDoc` is a snapshot of the contents at a moment in time while an `XMLCodeFile` object re-reads the file each time and so reflects any "asynchronous" changes.

### Objects from the Class

One can create these objects using coercion methods, e.g `as("file/name", "XMLCodeFile")` or `as("file/name", "XMLCodeDoc")`. One can also use `xmlCodeFile`.

### Slots

`.Data`:

  Object of class `"character"`

### Extends

Class `"character"`, from data part. Class `"vector"`, by class "character", distance 2.

### Methods

[[

  `signature(x = "XMLCodeFile", i = "ANY", j = "ANY")`: this method allows one to retrieve/access an individual R code element in the XML document. This is typically done by specifying the value of the XML element's "id" attribute.

coerce

  `signature(from = "XMLCodeFile", to = "XMLCodeDoc")`: parse the XML document from the "file" and treat the result as a `XMLCodeDoc` object.

source

  `signature(file = "XMLCodeFile")`: read and evaluate all the R code in the XML document. For more control, use `xmlSource`.

### Author(s)

Duncan Temple Lang

### See Also

`xmlSource`

### Examples

     src =  system.file("exampleData", "Rsource.xml", package = "XML")
       # mark the string as an XML file containing R code
     k = xmlCodeFile(src)

       # read and parse the code, but don't evaluate it.
     code = xmlSource(k, eval = FALSE)

       # read and evaluate the code in a special environment.
     e = new.env()
     ans = xmlSource(k, envir = e)
     ls(e)

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