Liquid Expressions

The following Liquid expressions are supported:

Common Variables

Workflow Variables

Use the following syntax to access a workflow variable:

{{ Variables.NameOfVariable }}

For example, given a workflow variable called FirstName with a value of “Alice”, the expression

Hello {{ Variables.FirstName }}

will result in Hello Alice

Using JSON variables

If your workflow variable is a JSON object, use this syntax:

{{ Variables.NameOfVariable | json | raw}}

For example: You have an API that returns a list of companies in JSON. You create an HTTP Request activity that calls the API, returning JSON. You can use this JavaScript to create your variable Companies: activities.getCompanies.ResponseContent()

The equivalent command in Liquid is {{Activities.getCompanies.ResponseContent}}

In this case you will use this syntax in your HTTP Response to use the variable Companies:

{{ Variables.Companies | json | raw}}

Iterating through liquid variables in JavaScript

See also Iteration for details.

Your web page will very likely use JavaScript to improve the user experience. You will want to build up JavaScript variables from the variables created with Set Variables or ObjectInstanceList activities, which you include in the workflow prior to displaying the HTML page.

For example, let’s say we have a ObjectInstanceList activity with the Name of ‘GetJobItems’. We want to write JavaScript for our web page that manipulates this data somehow, maybe filtering it based on a value on the page. JavaScript is needed because we want changes to be dynamic, and we don’t want to go back to the server for these UI changes.

Here is a sample, which uses a jobId set elsewhere on the page and filters data from the ‘GetJobItems’ activity:

<script>

        const jobItemsData = [
        {% for item in Activities.GetJobItems.ExpandedOutput %}
            { "objectId": {{item.ObjectId}}, "title": "{{item.Title}}", "jobId": {{item.Job.ObjectId}} },
        {% endfor %}
        ]; 

        function getJobItemsOptions(jobId, selectedJobItem) {
            const thisJobsItems = jobItemsData.filter(item => item.jobId === jobId);

            let jobItemOptions = '';
            thisJobsItems.forEach(item => {
                const isSelected = item.objectId == selectedJobItem ? 'selected' : '';
                jobItemOptions += `<option value="${item.objectId}" ${isSelected}>${item.title}</option>`;
            });
            return jobItemOptions;
        }

</script>

Input

Input values can be accessed using the following syntax:

{{ Input }}

Activity Output

To access a named activity’s output, use the following syntax:

{{ Activities.SomeActivityName.Output }}

CorrelationId

Returns the correlation ID (if any) of the currently executing workflow.

{{ CorrelationId }}

WorkflowInstanceId

Returns the workflow instance ID of the currently executing workflow.

{{ WorkflowInstanceId }}

WorkflowDefinitionId

Returns the workflow definition ID of the currently executing workflow.

{{ WorkflowDefinitionId }}

WorkflowDefinitionVersion

Returns the workflow definition version of the currently executing workflow.

{{ WorkflowDefinitionVersion }}

Configuration

Provides access to a .NET configuration value. See Configuration for more details on available configuration items in World of Workflows.

{{ Configuration.SomeSection }}

As an example, let’s say you have the following JSON in appsettings.json:

{
  "Elsa": {
    "Smtp": {
      "Host": "localhost",
      "Port": 2525
    }
  }
}

You can access the configured Port value using the following expression:

{{ Configuration.Elsa.Smtp.Port }}

Common Filters

json

A liquid filter that renders the specified value as a JSON string.

{{ Input | json }}

Example output:

{
  "SomeDocument": {
    "Title": "About Elsa Workflows"
  }
}

base64

A liquid filter that renders the specified value as a bas64 representation. The value is first converted to a string. If the value is an object, array, dictionary or datetime, it is first serialized using JsonConvert.SerializeObject before being encoded as base64.

{{ "Some string value" | base64 }}

Example output:

U29tZSBzdHJpbmcgdmFsdWU=

Workflow Filters

workflow_definition_id

Translates the specified workflow name or workflow tag into a workflow ID. This is useful for activities such as RunWorkflow which require a workflow ID to run.

Usage:

{{ "SomeWorkflowName" | workflow_definition_id }}

{{ "SomeWorkflowTag" | workflow_definition_id: tag }}

HTTP Variables

Request

Provides access to various properties on the current HTTP Request object:

{{ Request.QueryString }} {{ Request.ContentType }} {{ Request.ContentLength }} {{ Request.Form }} {{ Request.Protocol }} {{ Request.Path }} {{ Request.PathBase }} {{ Request.Host }} {{ Request.IsHttps }} {{ Request.Scheme }} {{ Request.Method }}

HTTP Filters

signal_url

A liquid filter that generates a fully-qualified absolute signal URL that will trigger the workflow instance from which this function is invoked.

Example:

{{ "MySignal" | signal_url }}

Example output:

https://localhost:5001/signals/trigger/{some base64 token}

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