If important issue updates occur outside of status changes, you cannot validate field entries using workflow Validators. That's where our powerful Event-based Actions come in. It offers a collection of triggers that will kick off one or more of JMWE's post functions to automate processes outside of workflows. One of its triggers - Issue Field Value Change - will trigger an action when an issue field value changes.


When a user edits an issue, validate field value input - if it's wrong, show the message and roll back to the previous value.

Viewing time 2 min 30 sec  

For your convenience, the steps from the above video have been outlined below.


When a user edits an issue, validate the field value input.

Here is how to validate input when a user changes a field, and display an in-app message when the input doesn't follow the required format to alert the user. Even better - automatically revert to the previous value.

  • Go to Event-based Actions in the JMWE App administration.
  • Click on "New event-based action" to create this automation.
  • Give it a name, such as "Check value of man hours."
  • In the Event trigger, select "Issue Field Value Changed."
  • In Fields to monitor, select "Man hours" field to watch for changes and to validate.

  • Optional: Select any one or more Projects to apply this to. Leave blank if this applies to all projects globally.
  • Optional: You can also select issue types to which this action will apply.
  • In the Scope section, add conditional execution by checking "Only apply to issues that match a Nunjucks condition."
  • In the "Nunjucks condition" field, navigate to and expand the "Issue Fields" tab, select "Man hours" in the field dropdown.
  • Referred to the field either by Name or ID, click on it to select and insert the proper field - issue.fields["Man hours"] - into the value section. We suggest using field IDs instead of names in case the name is edited in the future.
  • In the "Nunjucks condition" section, add >10 (to represent "greater than 10") after the name or ID of the field.

  • Press "Add post function." We'll configure a post function to display an "error" message to users if the field value entered is greater than 10.

  • Add "Display Message to User" post-function.
  • Input information you want to appear to users if the "Man hours" field entry is greater than 10.

  • Optional: select message type "Warning" and check "Automatically close message."
  • Save the post function.

  • Again, "Add post function". We'll configure a post function to roll back the field to the previous value.
  • Select the "Set field value" post function, and configure it.
  • Select Field "Man hours."
  • Type the following Nunjucks expression into the Value field:
    {{issue | fieldHistory( "Man hours" ) | last | field("from_string")}}
    This will set the previous field value. You can find all these snippets of code in our documentation.

  • Press "Save" to save the post function.
  • Press "Save" to save the Event-based Action.

  • All done.

See it all in action in the video above.