Revel message processing

Revel uses text files to provide international translation support. Revel supports language translation documentation, automatic area queries, cookie rewrites, nested messages and parameters.

Vocabulary

• Locale: Contains two parts, Language and Region, that indicate the user's language preferences, such as en-US
• Language: The language part of the locale, such as en Refer to ISO 639-1 codes for language identifiers.
• Region: The region portion of the locale, such as US For zone identifiers, refer to ISO 3166-1 alpha-2 codes.

The sample program

Revel handles message files and internationalization in a similar way to other frameworks. If you want to get started, you can refer revel/samples/i18n which contains all the basics.

The message file

The internationalization message is defined in the message file. T hese messages are used when rendering view templates (or elsewhere in the program). When you create a new message file, there are several rules to follow:

• All message files should be stored in the messages directory at the root of the application.
• The file extension is consistent with language and should be ISO 639-1 code.
• The message file should be UTF-8 encoded. Although not mandatory, it is best to follow this agreement.
• The message file must be a goconfig file that supports a number of goconfig features

Organize the message file

There are no restrictions on the file name of the message file; A s long as the extension is legitimate. T here is no limit to the number of files per language. W hen the application starts, Revel messages in the messages language directory and merges them according to the language. This means you are free to organize your message files.

For example, you might want to take the traditional approach of defining all of them in one file:

/app
    /messages
        messages.en
        messages.fr
        ...

Or create multiple files for each language and organize them by category:

/app
    /messages
        labels.en
        warnings.en
        labels.fr
        warnings.fr
        ...

Important: In multiple files in the same language, although the same message key can technically be defined, this can lead to unpredictable behavior. When more than one file is defined per language, be careful to keep your key unique so that when the files are merged, the key will not be overwritten!

Message key and value

The message file is a goconfig file. This means that the message should be defined in key-value format:

key=value

Take a chestnut:

greeting=Hello 
greeting.name=Rob
greeting.suffix=, welcome to Revel!

segment

Goconfig files are divided into multiple sections . ways present and contains messages defined when the segment is not specified. For example:

key=value

[SECTION]
key2=value2

key=value message message is implicitly placed in the default segment because it is not defined in a specified segment.

All messages in the message file should be in the default segment defined, unless they are used for a specific region (see Regions for more messages).

Note: Segment is goconfig feature.

Regional

Messages for a specific region should be defined in the same paragraph. R egion-specific messages should be defined in sections with the same name. F or example, suppose we want to display "Hello" "Hey" for UK users, "Howdy" To do this, we can define the following message greeting.en :

greeting=Hello

[GB]
greeting=Hey

[US]
greeting=Howdy

Revel parses greeting to Hello when English en is greeting as their preferred Hello Revel resolves the greeting with the message in the corresponding segment only en-US region is clearly defined, such as en-GB or en-GB greeting

Important: If an illegal area is defined, it is technically allowed, but they are never resolved.

Refers to the and parameters

Reference

Messages in a file can also refer to other messages. T his allows the user to form a single message from one or more other messages. T he syntax of the %(key)s . For example:

greeting=Hello 
greeting.name=Rob
greeting.suffix=, welcome to Revel!
greeting.full=%(greeting)s %(greeting.name)s%(greeting.suffix)s

Attention:

• References are the function of goconfig.
• Because message files can be merged, messages in other files can be referenced as long as they are defined as the same language.

Parameters

The message supports one or more parameters. T he parameters in the message are fmt rules as the fmt package. For example:

greeting.name_arg=Hello %s!

The parameters are parsed in the given order, and the reference resolves the message .

Resolve client language environment (locale)

To find out which language environment your users like, Revel looks for an available language environment in the following places:

1. Language cookies

   For each request, the framework looks for the application configuration i18n.cookie I f found, its value is assumed to be the current locale. When a cookie has been discovered, all other resolution methods will be skipped.

2. Accept-Language HTTP header

   For each request, Revel automatically parses Accept-Language E ach of these language environments is acquired and stored in Request instance according to the HTTP specification. This information is used to determine the current language environment for a later message resolution function.

   For more information, please refer to Parsed Accept-Language HTTP Header .

3. The default language

   When none of these methods find an available client language environment, the framework uses the default language defined in the i18n.default_language

If a message resolution fails, a specially formatted string containing the original message name is returned.

Note: Accept-Language information is always parsed and saved to the Request even if it already exists. In this case, the values in the header information can be used when they are needed, even if they have never been used by message resolution.

Check the current language environment

Applications can Request the current Request.Locale property. For example:

func (c App) Index() revel.Result {
    currentLocale := c.Request.Locale
    c.Render(currentLocale)
}

In the template, you can access the current language environment currentLocale variable in renderArgs For example:

    <p>Current preferred locale: {{.currentLocale}}</p>

Resolve the Accept-Language HTTP header information

If the program needs access Accept-Language HTTP header information, it can Controller from Request the Controller instance. AcceptLanguages AcceptLanguage contains all the values that are parsed from the respective header information, and the most appropriate value is the first in the slice. For example:

func (c App) Index() revel.Result {
    // 获取所有解析到的AcceptLanguage的字符串表示形式
    c.RenderArgs["acceptLanguageHeaderParsed"] = c.Request.AcceptLanguages.String()
    // 返回最合适AcceptLanguage实例
    c.RenderArgs["acceptLanguageHeaderMostQualified"] = c.Request.AcceptLanguages[0]

    c.Render()
}

For more information, please refer to the HTTP specification .

Resolve the message

Messages can be resolved in the controller or template.

Controller

Message Message(message string, args ...interface{}) the message using the current locale:

func (c App) Index() revel.Result {
    c.RenderArgs["controllerGreeting"] = c.Message("greeting")
    c.Render()
}

Template

Use the template function msg in the msg messages for the current locale. For example:

    <p>Greetings without arguments: {{msg . "greeting"}}</p>
    <p>Greetings: {{msg . "greeting.full.name" "Tommy Lee Jones"}}</p>

Note: The msg the msg function is msg . "message name" "argument" "argument" . If there are no arguments, you can ignore them.

Configuration

File	Options	Describe
app.conf	i18n.cookie	The name of the language cookie. The prefix of the Revel cookie should be used to avoid cookie name conflicts.
app.conf	i18n.default_language	The default locale, which is used without a preferred region.