Package 'xmlr'

Reference Class representing a non instantiable class

Description

An abstract base class with some utility methods

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An abstract reference class representing content that can belong to an Element

Description

#' @field m_parent the parent (if any)

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Reference Class representing an XML document

Description

The base container for the DOM

Usage

## S4 method for signature 'Document'
as.vector(x)

## S4 method for signature 'Document'
as.character(x)

Arguments

x	the object to convert

Details

Methods allow access to the root element as well as the DocType and other document-level information.

Methods (by generic)

• as.vector: as.vector(Document)

• as.character: as.character(Document)

Methods

getBaseURI()

return the URI from which this document was loaded

setBaseURI(uri)

Sets the effective URI from which this document was loaded

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Create a xmlr object tree based on parsing events

Description

Create a xmlr object tree based on parsing events

Methods

endDocument()

Event signalling parsing has completed

endElement(name)

end element event; @param name the element name

startDocument()

Event signalling parsing has begun

startElement(name, attributes)

start element event; @param name the element name, @param attributes a named list of attributes

text(text)

text event; @param text the character content of the Text node

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Element, A reference class representing an XML tag

Description

An XML element. Methods allow the user to get and manipulate its child elements and content, directly access the element's textual content, and manipulate its attributes.

Usage

## S4 method for signature 'Element'
as.vector(x)

## S4 method for signature 'Element'
as.character(x)

Arguments

x	the object to convert

Methods (by generic)

• as.vector: as.vector(Element)

• as.character: as.character(Element)

Fields

name

The local name of the element

contentList

all the children of this element

attributeList

a list of all the attributes belonging to this element

Methods

addAttributes(attributes)

Add the supplied attributes to the attributeList of this Element

addContent(content)

Appends the child to the end of the content list. return the parent (the calling object)

contentIndex(content)

Find the position of the content in the contentList or -1 if not found

getAttribute(name)

Get an attribute value

getAttributes()

Get the list of attributes

getChild(name)

Return the first child element matching the name

getChildren()

Get all the child Elements belong to this Element

getContent()

Returns the full content of the element as a List that may contain objects of type Text, Element, Comment, ProcessingInstruction, CDATA, and EntityRef

getName()

Return the name of this Element

getText()

Return the text content of this element if any

hasAttributes()

return TRUE if this element has any attributes, otherwise FALSE

hasChildren()

Return TRUE if this element has any child Element nodes

hasContent()

return TRUE if this element has any content, otherwise FALSE

hasText()

Return TRUE if this element has a Text node

removeContent(content)

Remove the specified content from this element

removeContentAt(index)

Remove the content at the given index and return the content that was removed

setAttribute(name, value)

Add or replace an attribute, parameters will be converted to characters

setAttributes(attributes)

Replace the attributes with this named list, NULL or empty list will remove all attributes, all values will be converted to characters

setName(name)

Set the name of this Element

setText(text)

Replace all content with the text supplied

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Common utility functions

Description

Common utility functions

Usage

isRc(x, clazz = "refClass")

Arguments

x	the object to check
clazz	the name of the class e.g. "Element" for the Element class. Optional, if omitted it checks that the object is a reference class

Value

A boolean indicating whether the object x belongs to the class or not

Functions

• isRc: Check if the object is a reference class, similar to isS4().

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Parse an xml string and create sax like events

Description

an XML parser based on an article on creating a quick and dirty xml parser by Steven Brandt: https://www.javaworld.com/article/2077493/java-tip-128–create-a-quick-and-dirty-xml-parser.html

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A general purpose linked stack

Description

A general purpose linked stack

Fields

size

the size of the stack (number of elements in the stack)

stackNode

an envronment containing the current element and the one under

Methods

peek()

Get the top element from the stack without changing it

pop()

Pull the top element from the stack removing it from the stack

push(val)

Add an element to the top of the stack

size()

Get the current size of the stack

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Reference class representing text content

Description

Reference class representing text content

as.vector for Text classes

as.character for Text classes

Usage

## S4 method for signature 'Text'
as.vector(x)

## S4 method for signature 'Text'
as.character(x)

Arguments

x	the object to convert

Details

An XML character sequence. Provides a modular, parentable method of representing text.

Methods (by generic)

• as.vector: as.vector(Text)

• as.character: as.character(Text)

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XML import functions

Description

XML import functions

Usage

parse.xmlstring(xml)

parse.xmlfile(fileName)

Arguments

xml	an xml character string to parse
fileName	the name of the xml file to parse

Value

a Document object

Functions

• parse.xmlstring: create a Document from a character string

• parse.xmlfile: create a Document from a xml file

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xmlr

Description

A package for creating, reading and manipulating XML providing and object model implemented with Reference Classes. This is perhaps especially useful when dealing with deeply nested XML structures.

Examples

library("xmlr")
doc <- Document$new()
root <- Element$new("table")
root$setAttribute("xmlns", "http://www.w3.org/TR/html4/")
doc$setRootElement(root)

root$addContent(
  Element$new("tr")
    $addContent(Element$new("td")$setText("Apples"))
    $addContent(Element$new("td")$setText("Bananas"))
)
table <- doc$getRootElement()
stopifnot(table$getName() == "table")
stopifnot(table$getAttribute("xmlns") == "http://www.w3.org/TR/html4/")

children <- table$getChild("tr")$getChildren()
stopifnot(length(children) == 2)
stopifnot(children[[1]]$getText() == "Apples")
stopifnot(children[[2]]$getText() == "Bananas")

# you can also parse character strings (or parse a file using parse.xmlfile(fileName))
doc <- parse.xmlstring("<foo><bar><baz val='the baz attribute'/></bar></foo>")

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Create a data frame from a xmlr Element

Description

This is a convenience method to take all the children of the given Element and create a data frame based on the content of each child where each child constitutes a row and the attributes or elements (including text) will constitute the columns. It assumes a homogeneous structure and the column names are takes from the first child

Usage

xmlrToDataFrame(element)

Arguments

element

the element to convert

Value

a data frame

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