README.md

In robertzk/rokogiri: Rokogiri (http://github.com/robertzk/rokogiri)

Rokogiri

An XML generator DSL in R, inspired by Ruby's Nokogiri.

Installing

Although Rokogiri is not currently available on CRAN, you can install the developmental version using:

devtools::install_github('robertzk/rokogiri')

Examples

Imagine we would like to produce the XML output for a CD catalog.

<catalog>
  <cd>
    <title>Empire Burlesque</title>
    <artist>Bob Dylan</artist>
    <country>USA</country>
    <company>Columbia</company>
    <price>10.9</price>
    <year>1985</year>
  </cd>
  <cd>
    <title>Hide your heart</title>
    <artist>Bonnie Tyler</artist>
    <country>UK</country>
    <company>CBS Records</company>
    <price>9.9</price>
    <year>1988</year>
  </cd>
</catalog>

To generate this file using Rokogiri, we can write the following R code.

rokogiri({
  catalog({
    cd({
      title("Empire Burlesque")
      artist("Bob Dylan")
      country("USA")
      company("Columbia")
      price(10.90)
      year(1985)
    })

    cd({
      title("Hide your heart")
      artist("Bonnie Tyler")
      country("UK")
      company("CBS Records")
      price(9.90)
      year(1988)
    })
  })
}) 

As you can see, the output is the appropriate XML. The advantage of using Rokogiri over other XML generators is that the code is very readable to write; it almost looks like English.

If you wish to provide your own XML converter, you can also produce a list as output.

rokogiri(output_type = 'list', {
  note({
    to("Tove")
    from("Jani")
    heading("Reminder")
    msg("Don't forget me this weekend!")
  })
})

Note that lists in R can share the same name multiple times! This means the list produced will not lose multiple records.

output <- rokogiri(output_type = 'list', {
  note({
    to("Tove")
  })
  note({
    to("Jim")
  })
})
stopifnot(names(output) == c("note", "note"))

If you have unorthodox tags in your XML, you can take advantage of another quirk of R. Any string surrounded in backticks or quotes can be used as a variable name.

rokogiri({
  "what-if-we-need"({
    "xml-tags"()
    "like-this"(2)
  })
})

The above example also shows that we can leave the argument to the function blank if it is an empty tag, and Rokogiri will produce the trailing slash.

License

This repository is distributed and licensed under the MIT License.

robertzk/rokogiri documentation built on May 27, 2019, 11:37 a.m.