Outputs and ARM Expressions

Outputs can be created in Farmer for any ARM Expression, Resource Name or any optional string. ARM Expressions are most useful in this case for referring to values that only exist at deployment time, such as connection strings.

Creating ARM Expressions

Farmer ARM expressions are in reality just wrapped strings, and are easy to create. For example, the code to create a Storage Key property is similar to this:

let buildKey accountName : ArmExpression =
    // Create the raw string of the expression
    let rawValue =
        $"concat('DefaultEndpointsProtocol=https;AccountName={accountName};AccountKey=', listKeys('{accountName}', '2017-10-01').keys[0].value)"

    // Wrap the raw value in an ARM Expression and return it
    ArmExpression.create rawValue

Notice that you do not wrap the expression in square brackets [ ]; Farmer will do this when writing out the ARM template.

Extracting the value of an ARM Expression

ARM expressions also have the following members on them:

  • Map - standard map
  • Bind - standard bind
  • Value - Returns the raw string value
  • Eval - Returns the string as a formatted ARM expression i.e. surround in []