Field Validation

RFE Forms is designed to support arbitrarily complex form field validations. Validation can be broken down into two types:

Date based validation
JavaScript expression based validation

Date based validation

This type of validation enforces certain conditions for date inputs. You can use date-based validation to guarantee that a Date input only allows:

Past or present dates
Past, present or future dates

{
  "label": "Date of Viral Load Result",
  "type": "obs",
  "questionOptions": {
    "rendering": "date",
    "concept": "163281AAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"
  },
  "validators": [
    {
      "type": "date",
      "allowFutureDates": "false"
    }
  ],
  "id": "dateOfViralLoadResult"
}

The above question will not accept future dates, and this is the default behaviour of the date validator. You can override this behaviour and permit future dates by setting allowFutureDates to true in your validator definition:

{
  "validators": [
    {
      "type": "date",
      "allowFutureDates": "true"
    }
  ]
}

Validation based on JavaScript expressions

When using expressions to validate form inputs, you must provide a JavaScript expression that resolves to a boolean value. Below is an expression-based example from a form used for collecting Cervical Cancer screening data:

{
  "type": "obs",
  "label": "HIV Status",
  "isExpanded": "true",
  "questions": [
    {
      "label": "What is your current HIV status?",
      "id": "hivStatus",
      "type": "obs",
      "required": "true",
      "questionOptions": {
        "rendering": "select",
        "concept": "9e4d6436-4040-46a3-a0ae-6dbc0acfe593",
        "answers": [
          {
            "concept": "a896f3a6-1350-11df-a1f1-0026b9348838",
            "label": "HIV positive"
          },
          {
            "concept": "a896d2cc-1350-11df-a1f1-0026b9348838",
            "label": "HIV negative"
          },
          {
            "concept": "a899b50a-1350-11df-a1f1-0026b9348838",
            "label": "Unknown"
          }
        ]
      },
      "validators": []
    },
    {
      "label": "Are you currently in HIV care or under ART?",
      "id": "currentlyOnArt",
      "type": "obs",
      "questionOptions": {
        "rendering": "select",
        "concept": "a8afba58-1350-11df-a1f1-0026b9348838",
        "answers": [
          {
            "concept": "a899b35c-1350-11df-a1f1-0026b9348838",
            "label": "Yes"
          },
          {
            "concept": "a899b42e-1350-11df-a1f1-0026b9348838",
            "label": "No"
          }
        ]
      },
      "validators": [
        {
          "type": "js_expression",
          "failsWhenExpression": "isEmpty(myValue) && hivStatus == 'a896f3a6-1350-11df-a1f1-0026b9348838'",
          "message": "Please indicate whether the client is currently in HIV care or under ART"
        }
      ]
    }
  ]
}

ℹ️

This question assumes that only HIV Positive clients are expected to be engaged in active HIV care.

A lot is going on in this example. Let us attempt to break it down step by step. The first question (id hivStatus) seeks to establish the client's HIV status. The next question (id currentlyOnArt) asks whether the client is actively receiving HIV care. Note that this second question has validation enabled.

{
  // ...
  "validators": [
    {
      "type": "js_expression",
      "failsWhenExpression": "isEmpty(myValue) && hivStatus == 'a896f3a6-1350-11df-a1f1-0026b9348838'",
      "message": "Please indicate whether the client is currently in HIV care or under ART"
    }
  ]
  // ...
}

The expression evaluates two conditions:

That this question(id: currentlyOnArt) gets answered. isEmpty(myValue) returns true if this question does not get answered, and false otherwise.
That question with hivStatus has the answer with the value a896f3a6-1350-11df-a1f1-0026b9348838. This value corresponds to the coded answer labelled HIV Positive.

The validation below restricts a user to only enter numbers only and while specifying the number of characters that can be entered. This works for fields like picking CCC numbers/Phone numbers.

{
	"label": "CCC Number",
	"type": "obs",
	"id": "cccNumber",
	"questionOptions": {
	      "concept": "162053AAAAAAAAAAAAAAAAAAAAAAAAAAAAAA",
				"rendering": "text",
				"maxLength": "10",
				"minLength": "10"
							},
							"validators": [
                    {
                      "type": "js_expression",
                      "failsWhenExpression": "!/^[0-9]*$/.test(myValue)",
                      "message": "CCC Number Should Be 10 Digits"
                    }
							  ]
}

The JavaScript expressions displays a fail message whenever a user tries to enter special characters or alphanumericals

The above Validation enforces numbers by use of JavaScript expressions

Expression Helpers Reference Hiding Fields