Best Practices for Building Mendix Widgets Efficiently

Key Takeaways

• Choose the right widget architecture: Selecting an appropriate widget approach is crucial for balancing functionality, scalability, and complexity.
• Understand trade-offs in development: Different widget strategies offer unique benefits and limitations, so align your choice with your project needs.
• Leverage Mendix’s built-in optimizations: Using native components simplifies development and provides efficient features like pagination and lazy loading.
• Plan for multi-widget complexities: Multi-widget setups require careful planning for state management, communication, and performance optimization.

Widget architecture – Making the right choice

When building a widget for Mendix, start with an architecture decision to determine the best approach. Your options depend largely on the widget’s complexity, and you’ll need to consider:

• A combination of widgets and Mendix components
• Container widgets
• Multiple widgets
• Loader widget approach

The first approach that comes to mind is creating one widget for the entire component. While this is simple for basic components, it becomes more challenging when the component is complex and includes multiple interactive actions.

Let’s explore this using a Todo List widget as an example. I’m going to discuss three different approaches for implementing the same widget.

Approach 1: Single widget as the list container

In this approach, you include the data source as part of the Todo List widget settings. The widget handles the rendering of the entire list, giving you complete control over the view. For example, you can render items vertically, horizontally, or as cards with custom layouts that aren’t possible with standard Mendix list components.

However, you’ll need to handle all list-related challenges within the widget, including but not limited to pagination, sorting, filtering, and lazy loading behavior. This means implementing these features from scratch rather than leveraging Mendix’s built-in optimizations.

Data handling complexity

The next significant challenge is handling actions and data updates. Since the data source is read-only, you cannot directly modify a Todo item. Instead, you need a dummy attribute to pass changes through microflows. This creates several implementation challenges:

Update operations

For simple operations like deleting an item or toggling a Todo’s status, you can implement separate actions. However, for more complex updates, you must either pass all changes to a single microflow or create separate microflows for each update action (toggle status, change title, change due date, change priority, etc.)

Performance considerations

When dealing with large datasets, you must implement your own pagination logic. This includes managing page size, handling scroll events for infinite scrolling, and ensuring smooth performance when users navigate through thousands of items.

Memory management

Since you’re handling the entire dataset within the widget, you need to be mindful of memory usage, especially on mobile devices or when dealing with large lists. Using pagination will mitigate the issue.

Action variables

From version 10.21.0 and above, it is possible to use action variables which makes the implementation easier than before. In earlier versions, the MF behind an action couldn’t have any parameters, and the MF had to retrieve the value of the dummy objects itself.

Configuration complexity

These additional settings make the widget setup more challenging for Mendix developers, requiring a solid understanding of several key configurations. Developers must learn how to configure dummy objects for data passing, create appropriate microflows for different actions, and ensure proper error handling to account for failed operations. Additionally, maintaining data consistency when multiple users are editing the same items demands extra care and planning.

Approach 2: List item widget

Another option is to leverage Mendix’s built-in list components, such as the Gallery widget, List View, or Data Grid. In this case, you only build the item widget and use it within the list container provided by Mendix.

This approach fundamentally separates concerns between different components. The Mendix list widget handles all the complex list management tasks: pagination, lazy loading, sorting, and filtering. Since these controls and patterns are familiar to Mendix developers, setup becomes significantly easier and follows established patterns.

Leveraging Mendix’s built-in optimizations

By using Mendix’s native list components, you automatically benefit from:

• Optimized data retrieval: Mendix automatically implements efficient data retrieval patterns, including the Retrieve & Aggregate optimization that reduces database queries when you only need counts rather than full datasets.
• Built-in pagination: Native pagination handling with configurable page sizes, reducing server load and improving client-side performance.
• Lazy loading: Automatic lazy loading of data as users scroll, preventing unnecessary data retrieval and improving initial page load times.
• Caching mechanisms: Mendix implements intelligent caching strategies that reduce redundant server requests.

Simplified data management

For adding new items, you can handle this outside the widget by displaying a pop-up page, a modal, or navigation to a separate form. This approach provides several benefits:

• Familiar patterns: Mendix developers can use standard page layouts, form validations, and styling approaches they already know.
• Access control: Easier to implement role-based access control using Mendix’s built-in security features.
• Form validation: Can leverage Mendix’s validation framework and error handling mechanisms.
• Responsive design: Automatically benefits from Mendix’s responsive design capabilities.

Editable data handling

In this approach, Todo items become editable (depending on the user’s object access permissions). Within the widget, implementing update logic becomes significantly simpler:

• Direct object manipulation: Can directly modify object attributes without requiring dummy objects.
• Simplified microflows: The microflow for changes is straightforward—it only needs to commit the object without requiring additional dummy parameters for operations.
• Real-time updates: Changes can be reflected immediately in the UI without complex state management.
• Validation integration: Can leverage Mendix’s built-in validation rules and error handling.

Approach 3: Multiple widgets

The third option involves building multiple interconnected widgets: a container widget that renders the list of items and one or more item widgets that render individual Todo items. This approach is particularly valuable when you need functionality not available in Mendix’s built-in list components, such as advanced drag-and-drop capabilities, custom layout algorithms, or complex inter-item interactions.

Scalability and reusability benefits

In our Todo example, if we build the container widget, we can reuse the item widget from our second approach above. Then, within the container widget, we can add advanced functionality like:

• Advanced drag-and-drop: Multi-directional dragging, drop zones with visual feedback, and complex reordering logic
• Custom layout algorithms: Masonry layouts, dynamic sizing based on content, or algorithmic positioning
• Bulk operations: Multi-select capabilities, batch editing, and complex selection patterns
• Real-time collaboration: Live updates when multiple users are editing the same list
• Advanced filtering: Custom filter interfaces, saved filter presets, and complex query builders

Implementation complexity considerations

Additionally, there are significant challenges when multiple widget instances on the same page need to communicate with each other:

• State synchronization: Ensuring all widgets stay in sync when data changes
• Event coordination: Managing complex event chains between widgets
• Performance optimization: Preventing unnecessary re-renders and data fetches
• Error handling: Gracefully handling failures in one widget without affecting others
• Droppable area configuration: Implementing preview mode in the widget to preview the droppable area in Studio Pro

State management challenges

Signaling and state management between widgets

One of the most significant complexities with multiple widgets is inter-widget communication and state management. When widgets need awareness of each other’s state—for example, when a user drags an item from one column to another in a Kanban board—you need a robust communication mechanism. One widget must hide the item while another displays it, all while maintaining data consistency and providing smooth user feedback.

This requires sophisticated data flow and synchronization between widgets, which isn’t straightforward and demands specific implementation techniques and careful consideration of edge cases.

Data flow patterns

For multiple widgets, data provision works similarly to single widgets, but you need to establish reliable patterns for passing data between widgets. You might use a container widget that holds child widgets, but there are important limitations to understand.

While React developers might assume they can pass props from parent to child components, this isn’t possible in Mendix pluggable widgets. If you render another widget inside a parent widget, the Mendix runtime will override any props you pass with data from the widget settings configured in Studio Pro. This means you cannot dynamically pass data through the component tree as you would in a typical React application.