1. What you will learn

In PAK there is the possibility to interpolate values when mapping values from Command to Command. This short Guide will show you how what is possible.

2. Basic Interpolation

All interpolations start off with a dollar sign and an open curly bracket that encloses the mapping together with a finalizing closed curly bracket.

An escaped interpolation like \${something} will not be recognized by the engine and kept as is.

Interpolation ⇒ ${InterpolationValue}
InterpolationValue ⇒ Environment | JsonPath

Interpolations may either enclose an environment variable or the json path to a variable stored in the datastore.

3. Environmental Interpolation

Environment ⇒ java(text) | env(text)

text: Name of the variable to fetch.

Environmental Interpolation refers to the acquisition of variables from the engines environment. To fetch a java runtime property use java, to fetch a systems environment variable use env.

4. Json Path Interpolation

JsonPath ⇒ JsonVariable(.JsonVariable)*
JsonVariable ⇒ ArrayIdentifier | text ArrayIdentifier?
ArrayIdentifier ⇒ [number] | [:] | [-:]

text: Name of the variable in the preceding element
number: Positive integer within the bounds of the preceding json array

Using json path interpolation, values from the datastore can be fetched and mapped directly from the datastore. The name of the first element in the json path must refer to a key that is present in the datastore.

When the preceding element is a json array, but no identifier was given, the whole json array is mapped to the declared variable and returned.

Special array identifiers:

  • [:] refers to the first element in the preceding array

  • [-:] refers to the last element in the preceding array

4.1. Examples

Given the following json object which is stored in the datastore under the key ‘obj’:

{
    "name" : "Max",
    "age" : 33,
    "hobbies" : [
        {
            "name" : "Soccer",
            "id" : 0
        },
        {
            "name" : "Coding",
            "id" : 1
        },
        {
            "name" : "Automating Workflows",
            "id" : 2
        }
    ]
}

  • obj.name → “Max”

  • obj.age → 33

  • obj.hobbies[1] → {“name” : “Coding”, “id” : 1}

  • obj.hobbies.[:] → {“name” : “Soccer”, “id” : 0}

  • obj.hobbies.name → [“Coding”, “Soccer”, “Automating Workflows”]

  • obj.hobbies.name[-:] → “Automating Workflows”