Import data with predicates

The form predicates feature allows you to import data from responses in another form. Use cases for this feature include:

• CMA Marietta used CFF for 2018 Balavihar Registration, and wants to do the same for 2019 Balavihar Registration. However, they would like for existing users' data to be imported, and for the grades to be bumped up one level.

• Sometimes some users might have made automatic "recurring payments" (such as Parivar) in the past through a previous form, which should automatically give them credit for the current year so they don't have to pay for it.

CFF supports a limited version of this through formOptions.predicate property.

Simple usage

Just add the following to formOptions:

{
    "predicate": {
        "formId": "abcd"
    }
}

The formId is the ID of the "predicate form", the form from which data needs to be imported. By default, the response that is owned by the current user from the predicate form is loaded; so this feature is currently only supported for forms that have loginRequired to true.

Note

Only responses that have status equal to PAID will be imported from a predicate; if the user has an unpaid response in the predicate form, it will not be imported.

You will also need to add the following to the predicate form's formOptions:

"successor": {
    "formId": "[form id of the current from]"
}

This is required as a security precuation, so that any form cannot claim an arbitrary form as a "predicate" and thus access its data.

Customizing warning text

By default, when a new response is created with a predicate, the following warning shows up at the top of the page:

To customize this text, edit the predicate.warningText property.

"predicate": {
    "warningText": "<b>Warning:</b> you are submitting a form based on old information from a predicate form."
}

Applying patches

Sometimes you may want to modify the data to apply patches, such as promoting children up a grade. This is how you do so:

{
    "predicate": {
        "formId": "abcd",
        "patches": [{"unwind": "/participants", "type": "walk", "items": ["A","B","C"], "path": "/grade"}]
    }
}

predicate.patches - A list of patches to apply to the response. All the patches get sequentially applied to the form data.

Above is an example of a "walk" patch, which will transform each "grade" and walk it up by 1 (A -> B, B -> C, otherwise will stay the same). The "unwind" parameter applies this patch to every element in the participants array.

Other examples of patches

Sets the value at the returning_family path to true.

{
    "type": "patch",
    "value": [
        { "op": "add", "path": "/returning_family", "value": true }
    ]
}

Removes the grade property for all objects in the array children.

{
    "type": "patch",
    "unwind": "/children",
    "value": [
        { "op": "remove", "path": "/grade" }
    ]
}