# Gettext

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`gettext` is an internationalization (i18n) and localization (l10n) system commonly used for writing multilingual programs. Gettext is a standard for i18n in different communities, meaning there is a great set of tooling for developers and translators.

## Installation

  1. Add `:gettext` to your list of dependencies in mix.exs:

    def deps do
      [{:gettext, "~> 0.8"}]

  2. Ensure `:gettext` is started before your application:

    def application do
      [applications: [:gettext, :logger]]

  3. Optional: add the `:gettext` compiler so your backends
    are recompiled when `.po` files change:

    def project do
      [compilers: [:gettext] ++ Mix.compilers]

[Documentation for `Gettext` is available on Hex][docs-gettext].

## Usage

To use gettext, you must define a gettext module:

defmodule MyApp.Gettext do
  use Gettext, otp_app: :my_app

And invoke the gettext API, based on the `*gettext` functions:

import MyApp.Gettext

# Simple translation
gettext "Here is one string to translate"

# Plural translation
number_of_apples = 4
ngettext "The apple is ripe",
         "The apples are ripe",
#=> "The apples are ripe"

# Domain-based translation
dgettext "errors", "Here is an error message to translate"

Translations in gettext are stored in Portable Object files (`.po`). Such files must be placed at `priv/gettext/en/LC_MESSAGES/domain.po`, where `en` is the locale and `domain` is the domain (the default domain is called `default`).

For example, the translation to `pt_BR` of the first two `*gettext` calls in the snippet above must be placed in the `priv/gettext/pt_BR/LC_MESSAGES/default.po` file with contents:

msgid "Here is one string to translate"
msgstr "Aqui está um texto para traduzir"

msgid "Here is the string to translate"
msgid_plural "Here are the strings to translate"
msgstr[0] "Aqui está o texto para traduzir"
msgstr[1] "Aqui estão os textos para traduzir"

`.po` are text based and can be edited directly by translators. Some may even use existing tools for managing them, such as [Poedit][poedit] or [][].

Finally, because translations are based on strings, your source code does not lose readability as you still see literal strings, like `gettext "here is an example"`, instead of paths like `translate "some.path.convention"`.

Read the [documentation for the `Gettext` module][docs-gettext-module] for more information on locales, interpolation, pluralization and other features.

## Workflow

`gettext` is able to automatically extract transformations from your source code, alleviating developers and translators from the repetitive and error-prone work of maintaining translation files.

When extracted from source, translations are placed into `.pot` files, which are template files. Those templates files can then be merged into translation files for each specific locale your application is being currently translated to.

In other words, the typical workflow looks like this:

  1. Add `gettext` calls to your source code. No need to touch translation files
     at this point as gettext will return the given string if no translation is

        gettext "Welcome back!"

  2. Once changes to the source are complete, run `mix gettext.extract` to automatically sync all existing entries to `.pot` (template files) in `priv/gettext`:

        mix gettext.extract

  3. `.pot` files can then be merged into locale-specific `.po` files with `mix gettext.merge`:

        # Merge .pot into all locales
        mix gettext.merge priv/gettext

        # Merge .pot into one specific locale
        mix gettext.merge priv/gettext --locale en

It is also possible to execute both the extract and merge operations in one step with `mix gettext.extract --merge`.

## License

Copyright 2015 Plataformatec

  Licensed under the Apache License, Version 2.0 (the "License");
  you may not use this file except in compliance with the License.
  You may obtain a copy of the License at

  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  See the License for the specific language governing permissions and
  limitations under the License.