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Variable Events

API callback events are available at different stages in the variable lifecycle. These events allow developers to intercept execution, modify inputs or results, and respond to success or failure scenarios. Event handlers provide fine-grained control over variable behavior without altering core logic.

Types of Variable Events:

  • On Before Update
  • On Result
  • On Before Dataset Ready
  • On Success
  • On Error
  • On Can Update

On Before Update​

The On Before Update event is invoked just before the variable triggers the service call. It provides access to the input data and allows you to: Validate inputs, Modify request payload.

    Page.createEmployeeonBeforeUpdate = function (variable, inputData, options) {
        // Validate mandatory input
        if (!inputData.employeeName) {
            App.Actions.notify({
                message: "Employee name is required",
                severity: "error"
            });
            return false; // Cancel the service call
        }

        // Add additional input before sending to service
        inputData.createdDate = new Date();

        return true; // Allow service call to proceed
    };
info

The onBeforeUpdate event behaves differently based on the variable type:

  • Database CRUD Variable (READ) → onBeforeListRecords
  • Database CRUD Variable (UPDATE) → onBeforeUpdateRecord
  • Database CRUD Variable (INSERT) → onBeforeInsertRecord
  • Database CRUD Variable (DELETE) → onBeforeDeleteRecord
  • All other variable types → onBeforeUpdate

On Before Dataset Ready​

This event is triggered after the service response is received but before the variable’s dataSet is updated.

    // Triggered before the dataSet is assigned to the variable
    Page.createEmployeeonBeforeDatasetReady = function (variable, data) {
        // Get selected device IDs from a widget
        let selectedDeviceIds = Page.Widgets.DevicePicker.selecteddevices
            .map(device => device.id);

        // Filter response data based on selected devices
        let filteredData = data.filter(emp =>
            selectedDeviceIds.includes(emp.devicesMappedId)
        );

        // Return modified data to update the variable's dataSet
        return filteredData;
    };

On Result​

The On Result event is triggered immediately after receiving a response from the service—regardless of success or failure.

     // Triggered when the service returns a response
     Page.createEmployeeonResult = function (variable, data, operation) {
         // If response contains a single object, convert it to array
         // This helps when binding to components like List etc
         if (data && !Array.isArray(data)) {
             variable.dataSet = [data];
         }

         // Store last operation performed for UI display
         Page.Variables.svEmployee.lastOperation.dataSet = operation;
     };

On Success​

The On Success event is triggered after the variable completes successfully and after the dataSet has been updated.

    // Triggered after successful execution
    Page.createEmployeeonSuccess = function (variable, data, operation) {
        // Show success notification
        App.Actions.notify({
            message: "Employee created successfully",
            severity: "success"
        });

        // Navigate to Employee Details page using returned ID
        App.navigate({
            pageName: "EmployeeDetails",
            params: {
                employeeId: data.id
            }
        });
        
        Page.Variables.getEmployees.invoke(); // Refresh employee list after update
        Page.Widgets.editEmployeeDialog.close();  // Close edit dialog
    };

On Error​

The On Error event is triggered only when the service call fails.

    // Triggered when the service call fails
    Page.createEmployeeonError = function (variable, error, operation) {
        // Display error message
        App.Actions.notify({
            message: error.message || "Unable to create employee",
            severity: "error"
        });

        // Highlight form fields if validation errors exist
        if (error.details && error.details.validationErrors) {
            Page.Widgets.employeeForm.setErrors(error.details.validationErrors)
        }

        Page.Widgets.retryUploadBtn.enable(); // Enable retry button after failure
    };

On Can Update​

The On Can Update event is triggered right before execution, after all validations and just before hitting the service. This event determines whether the variable is allowed to execute.

    // Triggered to decide whether the variable should execute
    Page.createEmployeeonCanUpdate = function (variable, data) {
        // Prevent execution if another request is in progress
        if (variable.isExecuting) {
            return false;
        }

        // Allow execution
        return true;
    };