How to create dynamic dropdowns in OutSystems that filter options based on prior selections?

Creating Dynamic Dropdowns in OutSystems

 

Creating dynamic dropdowns in OutSystems to filter options based on prior selections is an essential feature for developing interactive and user-friendly applications. This guide outlines a comprehensive, step-by-step approach to achieving dependent dropdown functionality.

 

Prerequisites

 

• An active OutSystems account with access to a development environment.
• Basic understanding of OutSystems Service Studio interface and reactive web applications.
• Knowledge of Entity and Aggregate creation in OutSystems.
• Familiarity with variables and expressions in OutSystems.

 

Understanding Dynamic Dropdowns

 

• Dynamic dropdowns display a list of options that adapt based on user interactions or selections in a previous dropdown.
• They enhance the user experience by providing relevant options, reducing data entry errors, and refining data capture efficiency.

 

Setting Up Your Data Entities

 

• Log in to your OutSystems environment and open or create the desired application where dynamic dropdowns are required.
• Create two or more entities to represent your dropdown data. For example, a "Country" entity and a "City" entity.
• In the "City" entity, include an attribute to establish a relationship with the "Country" entity, often a "CountryId" foreign key.

 

Constructing the Dropdown UI in OutSystems

 

• Open the page where you want to add the dynamic dropdowns.
• Drag and drop a Dropdown widget from the Toolbox onto the page for the first dropdown (e.g., "Country").
• Bind it to a List of your first entity (e.g., Countries) using an Aggregate to fetch data.
• Bind the selected value from this dropdown to a local variable (e.g., SelectedCountryId).

 

Implementing the OnChange Event for Dependency

 

• Select the first dropdown and navigate to its Events tab in the properties panel.
• Assign an OnChange event to this dropdown. This action will be triggered whenever the user changes the value.
• Create a new client action associated with this event to update the options of the dependent dropdown.

 

Configuring the Second Dropdown

 

• Add another Dropdown widget to the page for the dependent options (e.g., "City").
• Configure it to source its data based on the selected value from the first dropdown. This is done by applying a filter in the Aggregate: use the condition "City.CountryId = SelectedCountryId".
• Set this dropdown's data source to the filtered Aggregate, updating the List whenever the first dropdown changes.
• Bind its selected value to another local variable (e.g., SelectedCityId).

 

Testing Your Dynamic Dropdowns

 

• Publish and preview the application to ensure the dynamic dropdowns work correctly.
• Select a value in the first dropdown and observe the options in the second dropdown updating accordingly.
• Test different combinations to validate the specific options are correctly updated based on selections.

 

Enhancements and Best Practices

 

• Ensure efficient application by limiting the data fetched in Aggregates to relevant entities or rows only.
• Maintain a consistent user experience by using loading indicators when fetching data dynamically.
• Handle special cases, such as what happens when no option is available or selected in prior dropdowns.

 

By following these steps, you can effectively create and manage dynamic dropdowns in OutSystems that react to earlier user inputs, enhancing both functionality and user engagement within your applications. This approach not only leverages the power of the OutSystems platform but also drives improved data integrity and cohesive user interactions.