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ErlyDTL compiles Django Template Language to Erlang bytecode.

Supported tags: autoescape, block, blocktrans, comment, cycle, extends, filter, firstof, for, if, ifchanged, ifequal, ifnotequal, include, now, regroup, spaceless, ssi, templatetag, trans, widthratio, with

Unsupported tags: csrf_token, url

Supported filters: add, addslashes, capfirst, center, cut, date, default, default_if_none, dictsort, dictsortreversed, divisibleby, escape, escapejs, filesizeformat, first, fix_ampersands, floatformat, force_escape, format_integer, format_number, get_digit, iriencode, join, last, length, length_is, linebreaks, linebreaksbr, linenumbers, ljust, lower, make_list, phonenumeric, pluralize, pprint, random, random_num, random_range, removetags, rjust, safe, safeseq, slice, slugify, stringformat, striptags, time, timesince, timeuntil, title, truncatechars, truncatewords, truncatewords_html, unordered_list, upper, urlencode, urlize, urlizetrunc, wordcount, wordwrap, yesno

Unsupported filters: none

Project homepage:

Language reference:


To compile ErlyDTL, run


in this directory.

Template compilation

Four ways:

erlydtl:compile("/path/to/template.dtl", my_module_name)

erlydtl:compile("/path/to/template.dtl", my_module_name, Options)

erlydtl:compile(<<"<html>{{ foo }}</html>">>, my_module_name)

erlydtl:compile(<<"<html>{{ foo }}</html>">>, my_module_name, Options)

Options is a proplist possibly containing:

  • out_dir - Directory to store generated .beam files. If not specified, no .beam files will be created.

  • doc_root - Included template paths will be relative to this directory; defaults to the compiled template's directory.

  • custom_tags_dir - Directory of DTL files (no extension) includable as tags. E.g. if $custom_tags_dir/foo contains <b>{{ bar }}</b>, then {% foo bar=100 %} will evaluate to <b>100</b>. Get it?

  • custom_tags_modules - A list of modules to be used for handling custom tags. The modules will be searched in order and take precedence over custom_tags_dir. Each custom tag should correspond to an exported function, e.g.:

    some_tag(Variables, Context) -> iolist()

The Context is specified at render-time with the custom_tags_context option.

  • custom_filters_modules - A list of modules to be used for handling custom filters. The modules will be searched in order and take precedence over the built-in filters. Each custom filter should correspond to an exported filter, e.g.

    some_filter(Value) -> iolist()

If the filter takes an argument (e.g. "foo:2"), the argument will be also be passed in:

some_filter(Value, Arg) -> iolist()
  • vars - Variables (and their values) to evaluate at compile-time rather than render-time.

  • reader - {module, function} tuple that takes a path to a template and returns a binary with the file contents. Defaults to {file, read_file}. Useful for reading templates from a network resource.

  • compiler_options - Proplist passed directly to compiler:forms/2

  • force_recompile - Recompile the module even if the source's checksum has not changed. Useful for debugging.

  • locale - The locale used for template compile. Requires erlang_gettext. It will ask gettext_server for the string value on the provided locale. For example, adding {locale, "en_US"} will call {key2str, Key, "en_US"} for all string marked as trans ({% trans "StringValue" %} on templates). See README_I18N.

  • blocktrans_fun - A two-argument fun to use for translating blocktrans blocks. This will be called once for each pair of blocktrans block and locale specified in blocktrans_locales. The fun should take the form:

    Fun(Block::string(), Locale::string()) -> <<"ErlyDTL code">> | default

  • blocktrans_locales - A list of locales to be passed to blocktrans_fun. Defaults to [].

  • binary_strings - Whether to compile strings as binary terms (rather than lists). Defaults to true.

Helper compilation

Helpers provide additional templating functionality and can be used in conjunction with the custom_tags_module option above. They can be created from a directory of templates thusly:

erlydtl:compile_dir("/path/to/dir", my_helper_module_name)

erlydtl:compile_dir("/path/to/dir", my_helper_module_name, Options)

The resulting module will export a function for each template appearing in the specified directory. Options is the same as for compile/3.

Compiling a helper module can be more efficient than using custom_tags_dir because the helper functions will be compiled only once (rather than once per template).

Usage (of a compiled template)

my_compiled_template:render(Variables) -> {ok, IOList} | {error, Err}

Variables is a proplist, dict, gb_tree, or a parameterized module (whose method names correspond to variable names). The variable values can be atoms, strings, binaries, or (nested) variables.

IOList is the rendered template.

my_compiled_template:render(Variables, Options) -> 
        {ok, IOList} | {error, Err}

Same as render/1, but with the following options:

  • translation_fun - A fun/1 that will be used to translate strings appearing inside {% trans %} tags. The simplest TranslationFun would be fun(Val) -> Val end

  • locale - A string specifying the current locale, for use with the blocktrans_fun compile-time option.

  • custom_tags_context - A value that will be passed to custom tags.

    my_compiled_template:translatable_strings() -> [String]

List of strings appearing in {% trans %} tags that can be overridden with a dictionary passed to render/2.

my_compiled_template:translated_blocks() -> [String]

List of strings appearing in {% blocktrans %}...{% endblocktrans %} blocks; the translations (which can contain ErlyDTL code) are hard-coded into the module and appear at render-time. To get a list of translatable blocks before compile-time, use the provided blocktrans_extractor module.

my_compiled_template:source() -> {FileName, CheckSum}

Name and checksum of the original template file.

my_compiled_template:dependencies() -> [{FileName, CheckSum}]

List of names/checksums of templates included by the original template file. Useful for frameworks that recompile a template only when the template's dependencies change.

my_compiled_template:variables() -> [Variable::atom()]

Sorted list of unique variables used in the template's body. The list can be used for determining which variable bindings need to be passed to the render/3 function.

Differences from standard Django Template Language

The "regroup" tag must have an ending "endregroup" tag.


From a Unix shell, run:

make test

Note that the tests will create some output in tests/output.