suggestion: combobox value validation against picklist

Smart GWT Technical Q&A
1

I’d like to know what’s the best way to validate that user’s entry in a comboBoxItem is part of the pickList associated with it.

Quick context description:

  • The mainDS has a foreingKey on anotherDs. anotherDS is linked to anotherTable in my db.

  • the comboBoxItem is populated with the mainDS.foreignKey and the pickList is populated with values from anotherDS.

  • when the value is modified from the drop down, it’s fine.

  • My problem is when the users type a value in the comboBoxItem. How should I proceed with minimum round trip between client-server to validate the value entered by the user matches a value from the pickList ?

I’m currently using the ChangedHandler, catching every changedEvent (every time a user types a letter) and not updating the DS if the value is not in anotherTable.

thanks

2

There’s a built-in validator type (hasRelatedRecord) - see this sample.

3

In my case the picklist data is very dynamic.
So the following (more or less generic) custom validator works for me better.

public class IsOneOfDataArrivedValidator extends CustomValidator implements
		DataArrivedHandler {

	private RecordList dataArrivedList = null;

	@Override
	protected boolean condition(Object value) {
		boolean check = false;
		if (value != null) {
			if (dataArrivedList != null && dataArrivedList.getLength() > 0) {
				String fieldName = getFormItem().getName();
				for (int i = 0; i < dataArrivedList.getLength() && !check; i++) {
					Record r = dataArrivedList.get(i);
					String recordValue = r.getAttribute(getFormItem()
							.getValueFieldName());
					// attention data type conversion
					if (value instanceof Integer) {
						check = value.equals(Integer.valueOf(recordValue));
					} else {
						check = value.equals(recordValue);
					}
				}
			} else {
				check = false;
			}
		} else {
			check = true;
		}
		return check;
	}

	@Override
	public void onDataArrived(DataArrivedEvent event) {
		dataArrivedList = event.getData();
	}

}

Usage:

IsOneOfDataArrivedValidator validator = new IsOneOfDataArrivedValidator();
validator.setErrorMessage("error message");
itemLevel.addDataArrivedHandler(validator);
itemLevel.setValidators(validator);

Regards
Chris