R: Mustache-style string interpolation

epoxy_mustache {epoxy}

R Documentation

Mustache-style string interpolation

Description

A wrapper around the mustache templating language, provided by the whisker package. Under the hood, epoxy_mustache() uses whisker::whisker.render() to render the template, but adds a few conveniences:

The template can be passed in ... as a single string, several strings or as a vector of strings. If multiple strings are passed, they are collapsed with .sep ("\n" by default).
epoxy_mustache() can be vectorized over the items in the .data argument. If .data is a data frame, vectorization is turned on by default so that you can iterate over the rows of the data frame. The output will be a character vector of the same length as the number of rows in the data frame.

Usage

epoxy_mustache(
  ...,
  .data = parent.frame(),
  .sep = "\n",
  .vectorized = inherits(.data, "data.frame"),
  .partials = list()
)

Arguments

`...`	A string or a vector of strings containing the template(s). Refer to the mustache documentation for an overview of the syntax. If multiple strings are passed, they are collapsed with `.sep` (`"\n"` by default).
`.data`	A data frame or a list. If `.data` is a data frame, `epoxy_mustache()` will transform the data frame so that the template can be applied to each row of the data frame. To avoid this transformation, wrap the `.data` value in `I()`.
`.sep`	The separator to use when collapsing multiple strings passed in `...` into a single template. Defaults to `"\n"`.
`.vectorized`	If `TRUE` , `epoxy_mustache()` will vectorize over the items in `.data`. In other words, each item or row of `.data` will be used to render the template once. By default, `.vectorized` is set to `TRUE` if `.data` is a data frame and `FALSE` otherwise.
`.partials`	A named list with partial templates. See `whisker::whisker.render()` or the mustache documentation for details.

Value

A character vector of length 1 if .vectorized is FALSE or a character vector of the same length as the number of rows or items in .data if .vectorized is TRUE.

Examples

# The canonical mustache example
epoxy_mustache(
  "Hello {{name}}!",
  "You have just won {{value}} dollars!",
  "{{#in_ca}}",
  "Well, {{taxed_value}} dollars, after taxes.",
  "{{/in_ca}}",
  .data = list(
    name = "Chris",
    value = 10000,
    taxed_value = 10000 - (10000 * 0.4),
    in_ca = TRUE
  )
)

# Vectorized over the rows of .data
epoxy_mustache(
	"mpg: {{ mpg }}",
	"hp: {{ hp }}",
	"wt: {{ wt }}\n",
	.data = mtcars[1:2, ]
)

# Non-vectorized
epoxy_mustache(
	"mpg: {{ mpg }}",
	"hp: {{ hp }}",
	"wt: {{ wt }}",
	.data = mtcars[1:2, ],
  .vectorized = FALSE
)

# With mustache partials
epoxy_mustache(
  "Hello {{name}}!",
	"{{> salutation }}",
  "You have just won {{value}} dollars!",
  "{{#in_ca}}",
  "Well, {{taxed_value}} dollars, after taxes.",
  "{{/in_ca}}",
	.partials = list(
		salutation = c("Hope you are well, {{name}}.")
	),
	.sep = " ",
  .data = list(
    name = "Chris",
    value = 10000,
    taxed_value = 10000 - (10000 * 0.4),
    in_ca = TRUE
  )
)