[[{“value”:”
Introduction
In one of my recent SAPUI5 projects, I needed users to select a value from a predefined list. Since the list was quite large, I wanted to make the selection process as smooth as possible. Instead of using sap.m.Select, I went with sap.m.ComboBox because it lets users search for values by typing, making it much easier to find the right option.
Everything worked as expected until I started writing unit test cases. While testing different scenarios, I noticed that users weren’t limited to selecting values from the dropdown they could also type any value they wanted. Even if the entered text didn’t exist in the list, the ComboBox would still accept it.
It might seem like obvious behavior once you know how ComboBox works, but it was something I hadn’t considered during development. That’s when I realized that while the control offers a great user experience, it doesn’t automatically guarantee valid input.
We could have used a value help dialog for selection, but the requirement specifically called for a dropdown-based experience. That’s why the focus stayed on ComboBox and a deeper validation approach around it.
In this article, I’ll walk through the approach I used to keep the search functionality intact while ensuring users can only submit values that actually exist in the dropdown.
The Real Issue in Applications
In actual business scenarios, this becomes a real problem when data moves to the backend. Users may enter free text in the ComboBox and it still gets treated as valid input even if it doesn’t exist in the master data.
This can lead to invalid payloads, failed backend validations, and inconsistent business data in reports. What starts as a small UI behavior can quickly turn into a data integrity issue.
That’s why, when using sap.m.ComboBox for strictly controlled fields like Country, Plant, or Company Code, frontend validation becomes essential before processing the input.
Picture 1: Understanding the ComboBox and It’s Behaviour
The Approach I Used
To handle this, I added a simple validation on the ComboBox events. The idea was straightforward—accept the input only if it matches a valid item from the list.
I mainly relied on the change event along with getSelectedKey(). If the user entered something that didn’t match any item, I cleared the value, showed an error state using setValueState(“Error”), and displayed a meaningful message.
I also used selectionChange to reset the error state when a valid option was selected from the dropdown, ensuring a smoother user experience.
Implementation
The validation was handled mainly using the change and selectionChange events. The goal was to ensure that only valid values from the dropdown are accepted, while giving clear feedback when something incorrect is entered.
XML View Code: (.xml file)
<!– XML View –>
<ComboBox
id=”countryCombo”
items=”{path: ‘/Countries’}”
selectionChange=”.onSelectionChange”
change=”.onChange”>
<core:Item
key=”{CountryCode}”
text=”{CountryName}” />
</ComboBox>
Controller Code: (.js file)
// Controller Logic
onChange: function (oEvent) {
const oCombo = oEvent.getSource();
const sValue = oCombo.getValue().trim();
const sKey = oCombo.getSelectedKey();
if (!sValue || !sKey) {
oCombo.setValue(“”);
oCombo.setValueState(“Error”);
oCombo.setValueStateText(“Please select a valid value from the list.”);
return;
}
oCombo.setValueState(“None”);
},
onSelectionChange: function (oEvent) {
oEvent.getSource().setValueState(“None”);
}
Best Practices
When working with sap.m.ComboBox, validation should always be treated as part of the design, not an afterthought.
Use getSelectedKey() instead of relying only on getValue(), since free text input is always possible. Trim user input before validation to avoid whitespace-related issues.
Always provide clear ValueState feedback so users immediately understand what went wrong. Also, reset the error state on valid selection using selectionChange to improve usability.
Finally, even if frontend validation is in place, always enforce the same checks at the backend to ensure data integrity.
Picture 2: Data Integrity
Alternative Approaches
Depending on the requirement, there are a few other ways to handle this.
If search is not critical and the list is small, sap.m.Select is a simpler option since it only allows predefined selections.
In some cases, developers try disabling free typing in ComboBox, but that removes the search flexibility, which is often the main reason for choosing it in the first place.
Another option is model or backend-level validation, but that should always complement frontend checks rather than replace them.
Picture 3: Right Approaches for Handling Selections
Key Takeaway & Conclusion:
A ComboBox is not automatically restricted to its items. If your requirement is to allow only predefined values, you must explicitly validate the user input before processing it.
The goal is not to remove the flexibility of sap.m.ComboBox, but to balance it—keep the search experience intact while ensuring only valid, business-approved values make it to the backend.
Kindly Note: We could have used a value help dialog for selection, but the requirement specifically called for a dropdown-based experience. That’s why the focus stayed on sap.m.ComboBox and a deeper validation approach around it.
If you have any alternative effective solutions, please feel free to share your thoughts and so everyone can learn from each other.
Thank you for taking the time to read this blog! If you found this helpful, i would love to hear your thoughts, feedback or questions in the comments. Let’s keep learning and growing together!
I’m still new to blogging, so if you notice anything that could be improved or corrected, please don’t hesitate to let me know!!
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