Define a Validation Rule in an MDK App

You will add a rule to the Update action to run the validation before saving any data. If the validation rule is successful, the Update action will save the changes as expected. If the validation rule fails, the end-user receives the validation failure message telling them useful information so they can fix the problem before continuing.

1. Open Customers_UpdateEntity.action by double clicking on the action in the project explorer pane.

2. Expand the Common Action Properties and click the Create a rule icon to create a new Validation Rule.

   

3. Keep the default selection for the Object Type as Rule and Folders path. Click OK.

   

4. In the Base Information step, enter the Rule Name as EmailValidation and then click Finish.

   

   You can find more details about writing a Rule.

5. Replace the generated snippet with below code.

   JavaScript Copy

   /**
   * Describe this function...
   * @param {IClientAPI} context
   */
   export default function EmailValidation(context) {
       //The following evaluateTargetPath will retrieve the current value of the email control
       if ((context.evaluateTargetPath('#Control:FCEmail/#Value').indexOf('@')) === -1) {
           //If email value does not contain @ display a validation failure message to the end-user
           context.executeAction('/demosampleapp/Actions/ValidationFailure.action');
       } else {
           //If @ is present in the email value, return true to indicate validation is successful
           return true;
       }
   }

   This rule will handle validation if a @ symbol exists in the email address. In this validation rule, you will grab the data entered by the end-user, validate it and check for the @ symbol then return true if the email address is of a valid format or false if it is not. The returning result of the validation rule can be used in the Update action to determine whether the action succeeds or fails.

   The indexOf() method returns the index within the calling String object of the first occurrence of the specified value and -1, if no occurrence is found.

   In above code there is a reference to ValidationFailure.action, which doesn’t yet exist in your metadata project. You will create this action in next step.

6. In the generated EmailValidation.js rule, double-click the red line. You will notice a bulb icon suggesting some fixes, click on it, select MDK: Create action for this reference, and click Message.

   

7. Provide the below information in the ValidationFailure.action:

   Field	Value
   Message	Email address is not in the correct format recipient @ domain . domaintype
   Title	Validate Email
   OKCaption	OK
   OnOK	--None--
   CancelCaption	leave it blank
   OnCancel	--None--

   

You will now deploy the updated project to your MDK client.

Click the Deploy option in the editor’s header area, and then choose the deployment target as Mobile Services .

Make sure you are choosing the right device platform tab above.

Once you complete this tutorial you can continue with Enhance Your First MDK App with Additional Functionalities mission.