How to present state and country picklists with dependency logic in a Lightning Component?

Question

It's not too hard to present the Contact/Account state and country picklists themselves, but the dependency filtering where when you select "United States" as the country only the 50 or so relevant states are presented seems hard to do.

I don't see anything helpful in the lightning:inputAddress component. The subject is not mentioned in the lightning:inputField documentation so I am assuming the dependency logic not addressed there - or is it?

I haven't found a paid or free component on the AppExchange for this.

Beyond that we seem to be back in the territory of each having to get hold of the data somehow - e.g. via a web service call to the User Interface API or in Apex through this somewhat hacky documented but hard to leverage in Apex serializing/deserializing technique - and then each writing our own client-side logic.

Is there a good ready made solution to this problem that I haven't found yet?

PS

Did some experimenting with Benj's serializing/deserializing technique and with a bit of caching added the data for the default state and country picklists can be generated in about 100ms. So if no better solution comes along, I'll use that code - added below in an answer - at the server-side and write a bit of custom client-side code.

Answer 1

For anyone interested, this is my mild reworking of Benj's code that works out the dependencies in Apex code. These changes are mainly aimed at performance (reducing CPU time from over a second to around 100ms for the default country/state dependency):

• Caches conversion of validFor to controlling field picklist indexes so instead of calculating a few hundred of those only 9 calculations are needed for the default county/state picklists
• Finds the "1"'s without checking every one of the "0" values in the bits string
• Only deserializes the picklist entry values needed for the code
• Ignores the picklist entries that are inactive
• Outputs the values (code) not the labels so the resulting data is smaller Turns out that the state codes are not unique so the state label does need to be output

The output is of this form:

{
  ...
  "CV" : [ ],
  "CA" : [ "AB", "BC", "MB", "NB", "NL", "NT", "NS", "NU", "ON", "PE", "QC", "SK", "YT" ],
  "CM" : [ ],
  ...
}

and the code is:

public class DependentPicklists {

    private static final String BASE_64_CHARS = ''
            + 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'
            + 'abcdefghijklmnopqrstuvwxyz'
            + '0123456789+/';

    private class PicklistEntryBean {
        public Boolean active {get; set;}
        public String value {get; set;}
        public String validFor {get; set;}
    }

    private Map<String, Set<Integer>> cache;

    public Map<String, List<String>> controllingToDependentValues(SObjectField controlling, SObjectField dependent) {

        Map<String, List<String>> results = new Map<String, List<String>>();

        if (controlling != null && dependent != null) {

            cache = new Map<String, Set<Integer>>();

            List<String> controllingValues = new List<String>();

            for (PicklistEntry pe : controlling.getDescribe().getPicklistValues()) {
                if (pe.isActive()) {
                    results.put(pe.getValue(), new String[] {});
                    controllingValues.add(pe.getValue());
                }
            }

            for (PicklistEntryBean pe : picklistEntryBeans(dependent.getDescribe().getPicklistValues())) {
                if (pe.active) {
                    for (Integer index : validForToIndices(pe.validFor)) {
                        results.get(controllingValues.get(index)).add(pe.value);
                    }
                }
            }

        }

        return results;
    }

    private Set<Integer> validForToIndices(String validFor) {

        Set<Integer> indices = cache.get(validFor);
        if (indices == null) {
            indices = new Set<Integer>();

            String validForBits = base64ToBits(validFor);
            for (Integer i = validForBits.indexOf('1'); i >= 0; i = validForBits.indexOf('1', i + 1)) {
                indices.add(i);
            }

            cache.put(validFor, indices);
        }

        return indices;
    }

    private static String decimalToBinary(Integer val) {

        String bits = '';
        while (val > 0) {
            Integer remainder = Math.mod(val, 2);
            val = Integer.valueOf(Math.floor(val / 2));
            bits = String.valueOf(remainder) + bits;
        }
        return bits;
    }

    private static String base64ToBits(String validFor) {

        if (String.isEmpty(validFor)) return '';

        String validForBits = '';
        for (Integer i = 0; i < validFor.length(); i++) {
            String thisChar = validFor.mid(i, 1);
            Integer val = BASE_64_CHARS.indexOf(thisChar);
            String bits = decimalToBinary(val).leftPad(6, '0');
            validForBits += bits;
        }
        return validForBits;
    }

    private static PicklistEntryBean[] picklistEntryBeans(List<PicklistEntry> pes) {

        return (List<PicklistEntryBean>) JSON.deserialize(JSON.serialize(pes), List<PicklistEntryBean>.class);
    }
}