Mustache for R

Description

Whisker is a templating engine for R conforming to the Mustache specification. Mustache is a logicless templating language, meaning that no programming source code can be used in your templates. This may seem very limited, but Mustache is nonetheless powerful and has the advantage of being able to be used unaltered in many programming languages. For example it make it very easy to write a web application in R using Mustache templates and where the browser can template using javascript's "Mustache.js"

Details

Mustache (and therefore whisker) takes a simple but different approach to templating compared to most templating engines. Most templating libraries for example Sweave and brew allow the user to mix programming code and text throughout the template. This is powerful, but ties a template directly to a programming language. Furthermore that approach makes it difficult to seperate programming code from templating code.

Whisker on the other hand, takes a Mustache template and uses the variables of the current environment (or the supplied list) to fill in the variables.

Examples

template <- 
'Hello {{name}}
You have just won ${{value}}!
{{#in_ca}}
Well, ${{taxed_value}}, after taxes.
{{/in_ca}}'

data <- list( name = "Chris"
            , value = 10000
            , taxed_value = 10000 - (10000 * 0.4)
            , in_ca = TRUE
            )

whisker.render(template, data)




base <-
'<h2>Names</h2>
{{#names}}
  {{> user}}
{{/names}}'

user <- '<strong>{{name}}</strong>'

names <- list(list(name="Alice"), list(name="Bob"))

whisker.render(base, partials=list(user=user))

enclose a key with delimiters

Description

enclose a key with delimiters

Usage

delimit(x, delim = tag2delim())

Arguments

Is a value falsey according to Mustache specifications?

Description

This function is used to test a value before rendering

Usage

isFalsey(x)

Arguments

Value

TRUE if falsey, otherwise FALSE

Create an iteration list from a R object

Description

In some case it is useful to iterate over a named list or vector iteratelist will create a new unnamed list with name value members: each item will be a list where 'name' is the corresponding name and 'value' is the original value in list x.

Usage

iteratelist(x, name = "name", value = "value")

Arguments

Value

unnamed list with name value lists

Examples

# create an iteration list from a named vector
x <- c(a=1, b=2)
iteratelist(x)

# iterate over the members of a list
x <- list(name="John", age="30", gender="male")
iteratelist(x, name="variable") 

# iterate over an unnamed vector
values <- c(1,2,3,4)

template <- 
'{{#values}}
* Value: {{.}}
{{/values}}'

whisker.render(template)

#or 

values <- iteratelist(values, value="count")

template <- 
'{{#values}}
* Value: {{count}}
{{/values}}'

whisker.render(template)

Split a data.frame or matrix into rows

Description

Utility function for splitting a data.frame into rows. In a whisker template it can be useful to iterate over the rows of a data.frame or matrix. For example rendering a table in HTML.

Usage

rowSplit(x, ...)

Arguments

Examples

dat <- head(InsectSprays)
dat <- unname(rowSplit(dat))

template <- 
"{{#dat}}
count: {{count}}, spray: {{spray}}\n
{{/dat}}"

whisker.render(template)

Split a character in three parts

Description

It differs from strsplit in that it only splits on the first occurrence and returns all parts of the string given

Usage

rxsplit(x, pattern)

Arguments

change a delimiter tag into two escaped characters

Description

change a delimiter tag into two escaped characters

Usage

tag2delim(tag = "{{ }}", escape = TRUE)

Arguments

escape basic HTML characters

Description

This method is called for normal mustache keys

Usage

whisker.escape(x)

Arguments

Value

HTML escaped character

Logicless templating

Description

Logicless templating

Usage

whisker.render(template, data = parent.frame(), partials = list(),
  debug = FALSE, strict = TRUE)

Arguments

Value

character with rendered template

Note

By default whisker applies html escaping on the generated text. To prevent this use {{{variable}}} (triple) in stead of {{variable}}.

Examples

template <- "Hello {{place}}!"
place <- "World"

whisker.render(template)

# to prevent html escaping use triple {{{}}}
template <- 
  "I'm escaped: {{name}}
And I'm not: {{{name}}}"

data <- list( name = '<My Name="Nescio&">')
whisker.render(template, data)
# I'm escaped: &lt;My Name=&quot;Nescio&amp;&quot;&gt;
# And I'm not: <My Name="Nescio&">