Package 'jinjar'

Title: Template Engine Inspired by 'Jinja'
Description: Template engine powered by the 'inja' C++ library. Users write a template document, using syntax inspired by the 'Jinja' Python package, and then render the final document by passing data from R. The template syntax supports features such as variables, loops, conditions and inheritance.
Authors: David Hall [aut, cre, cph] , Lars Berscheid [cph] (Author of bundled inja library), Niels Lohmann [cph] (Author of bundled json library)
Maintainer: David Hall <david.hall.physics@gmail.com>
License: MIT + file LICENSE
Version: 0.3.1.9000
Built: 2024-02-29 07:40:47 UTC
Source: https://github.com/davidchall/jinjar

Help Index


Configure the templating engine

Description

Create an object to configure the templating engine behavior (e.g. customize the syntax). The default values have been chosen to match the Jinja defaults.

Usage

jinjar_config(
  loader = NULL,
  block_open = "{%",
  block_close = "%}",
  variable_open = "{{",
  variable_close = "}}",
  comment_open = "{#",
  comment_close = "#}",
  line_statement = NULL,
  trim_blocks = FALSE,
  lstrip_blocks = FALSE,
  ignore_missing_files = FALSE
)

default_config()

Arguments

loader

How the engine discovers templates. Choices:

  • NULL (default), disables search for templates.

  • Path to template directory.

  • A loader object.

block_open, block_close

The opening and closing delimiters for control blocks. Default: ⁠"{%"⁠ and ⁠"%}"⁠.

variable_open, variable_close

The opening and closing delimiters for print statements. Default: "{{" and "}}".

comment_open, comment_close

The opening and closing delimiters for comments. Default: "{#" and "#}".

line_statement

The prefix for an inline statement. If NULL (the default), inline statements are disabled.

trim_blocks

Remove first newline after a block. Default: FALSE.

lstrip_blocks

Remove inline whitespace before a block. Default: FALSE.

ignore_missing_files

Ignore include or extends statements when the auxiliary template cannot be found. If FALSE (default), then an error is raised.

Value

A "jinjar_config" object.

Note

The equivalent Jinja class is Environment, but this term has special significance in R (see environment()).

Examples

jinjar_config()

Template loaders

Description

Loaders are responsible for exposing templates to the templating engine.

path_loader() loads templates from a directory in the file system.

package_loader() loads templates from a directory in an R package.

list_loader() loads templates from a named list.

Usage

path_loader(...)

package_loader(package, ...)

list_loader(x)

Arguments

...

Strings specifying path components.

package

Name of the package in which to search.

x

Named list mapping template names to template sources.

Value

A "jinjar_loader" object.

See Also

The loader is an argument to jinjar_config().

Examples

path_loader(getwd())

package_loader("base", "demo")

list_loader(list(
  header = "Title: {{ title }}",
  content = "Hello {{ person }}!"
))

Parse a template

Description

Sometimes you want to render multiple copies of a template, using different sets of data variables. parse_template() returns an intermediate version of the template, so you can render() repeatedly without re-parsing the template syntax.

Usage

parse_template(.x, .config)

## S3 method for class 'character'
parse_template(.x, .config = default_config())

## S3 method for class 'fs_path'
parse_template(.x, .config = default_config())

Arguments

.x

The template. Choices:

  • A template string.

  • A path to a template file (use fs::path()).

.config

The engine configuration. The default matches Jinja defaults, but you can use jinjar_config() to customize things like syntax delimiters, whitespace control, and loading auxiliary templates.

Value

A "jinjar_template" object.

See Also

Examples

x <- parse_template("Hello {{ name }}!")

render(x, name = "world")

Print a template

Description

Once a template has been parsed, it can be printed with color highlighting of the templating blocks.

Usage

## S3 method for class 'jinjar_template'
print(x, ..., n = 10)

Arguments

x

A parsed template (use parse_template()).

...

These dots are for future extensions and must be empty.

n

Number of lines to show. If Inf, will print all lines. Default: 10.

Examples

input <- '<!DOCTYPE html>
<html lang="en">
<head>
    <title>{{ title }}</title>
</head>
<body>
    <ul id="navigation">
    {% for item in navigation -%}
        <li><a href="{{ item.href }}">{{ item.caption }}</a></li>
    {% endfor -%}
    </ul>
{# a comment #}
</body>
</html>'

x <- parse_template(input)

print(x)

print(x, n = Inf)

Render a template

Description

Data is passed to a template to render the final document.

Usage

render(.x, ...)

## S3 method for class 'character'
render(.x, ..., .config = default_config())

## S3 method for class 'fs_path'
render(.x, ..., .config = default_config())

## S3 method for class 'jinjar_template'
render(.x, ...)

Arguments

.x

The template. Choices:

...

<dynamic-dots> Data passed to the template.

By default, a length-1 vector is passed as a scalar variable. Use I() to declare that a vector should be passed as an array variable. This preserves a length-1 vector as an array.

.config

The engine configuration. The default matches Jinja defaults, but you can use jinjar_config() to customize things like syntax delimiters, whitespace control, and loading auxiliary templates.

Value

String containing rendered template.

See Also

Examples

# pass data as arguments
render("Hello {{ name }}!", name = "world")

# pass length-1 vector as array
render("Hello {{ name.0 }}!", name = I("world"))

# pass data programmatically
params <- list(name = "world")
render("Hello {{ name }}!", !!!params)

# render template file
## Not run: 
render(fs::path("template.txt"), name = "world")

## End(Not run)