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Define and Access Values

A Value is a named reference to a piece of static data stored by Atlas that you can access in Atlas Functions. Values provide an alternative to hardcoding configuration constants directly into your Functions.

In other words, Values allow you to separate deployment-specific configuration data from the business logic of your app.

Values can resolve to two types of data:

Plain text: Resolves to a regular JSON object, array, or string Value that you define.
Secret: Resolves to a Secret Value that you define.

Define a Value

You can define a new Value from the UI or using the App Services CLI.

In Atlas, go to the Triggers page for your project.

If it's not already displayed, select the organization that contains your project from the Organizations menu in the navigation bar.
If it's not already displayed, select your project from the Projects menu in the navigation bar.
In the sidebar, click Triggers under the Streaming Data heading.

The Triggers page displays.

Navigate to the Values Page

Click the Linked App Service: Triggers link.
In the sidebar, click Values under the Build heading.
Click Create a Value.

Name the Value

Enter a unique Value Name. This name is how you refer to the Value in Functions.

Note

Value Name Restrictions

Value names cannot exceed 64 characters and may only contain ASCII letters, numbers, underscores, and hyphens. The first character must be a letter or number.

Define the Value

Select the Value type.
Define either a plain text value or link to a Secret value:
- To define a plain text value, Custom Content and enter the plain text Value in the input box.
- To link to an existing Secret's value, select Link to Secret and select the Secret from the dropdown.
- To link to a new Secret value, select Link to Secret, then enter the new Secret's name and the new Secret's value in the input box that appears.
For more information on creating a Secret, see Create a Secret.

Save the Value

After you have named and defined the new Value, click Save.

Once saved, you can immediately access the Value in your Functions.

Authenticate a MongoDB Atlas User

Use your MongoDB Atlas Administration API Key to log in to the App Services CLI:

appservices login --api-key="<API KEY>" --private-api-key="<PRIVATE KEY>"

Pull Your App's Latest Configuration Files

Run the following command to get a local copy of your configuration files:

appservices pull --remote=<App ID>

By default, the command pulls files into the current working directory. You can specify a directory path with the optional --local flag.

Add the Value Configuration

Add a JSON configuration file for the new Value to the values subdirectory of your local application:

touch values/<ValueName>.json

Each Value is defined in its own JSON file. For example, a Value named myValue would be defined in the file /values/myValue.json.

The configuration file should have the following general form:

values/<ValueName>.json

{
   "name": "<Value Name>",
   "from_secret": <boolean>,
   "value": <Stored JSON Value|Secret Name>
}

Field	Description
`name`	A unique name for the Value. This name is how you refer to the Value in Functions and rules.
`from_secret`	Default: `false`. If `true`, the Value exposes a Secret instead of a plain-text JSON Value.
`value`	The stored data the Value exposes when referenced: If `from_secret` is `false`, `value` can be a standard JSON string, array, or object. If `from_secret` is `true`, `value` is a string that contains the name of the Secret the Value exposes.

Deploy Your Changes:

Run the following command to deploy your changes:

appservices push

Access a Value

You can access a Value's stored data from an Atlas Function using the context.values module.

context.values.get("<Value Name>")

For example, the following Function returns true when the active user's id is included in the plain text array Value adminUsers:

Example Function that uses a Value

exports = function() {
   const adminUsers = context.values.get("adminUsers");
   const isAdminUser = adminUsers.indexOf(context.user.id) > 0;
   return isAdminUser;
}

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