Dependent drop down not working dynamically

Hi All,

As part of practice and POC purpose. There was requirement like i have created three drop down fields on UI and also there are also Three tables created DB(Tables- States, Cities, Towns).

Sates- drop down and City-Drop down working as expected based on selected state value cities were displaying but based on selected City value towns drop down field values not showing up.

null parameter was passing when i checked local variables. i tried different ways but not able to achieve this.

could you please help on this.  

below code for reference

a!localVariables(
local!stateData: rule!KT_getStateDataById(),
local!stateName: property(local!stateData, "state",null),
local!stateId: property(local!stateData,"id",null),
local!cityname: rule!KT_getCityByStateId(stateId:ri!stateid ),

 local!townname: rule!KT_getTownNameByCityId(cityid: ri!cityId),

{
a!sectionLayout(
label: "",
contents: {
a!columnsLayout(
columns: {
a!columnLayout(
contents: {
a!dropdownField(
choiceLabels: local!stateName,
choiceValues: local!stateId,
label: "States",
labelPosition: "ABOVE",
placeholder: "--- Select a Value ---",
value: ri!stateid,
saveInto: {
ri!stateid,
a!save(ri!cityName,null)
},
searchDisplay: "AUTO",
validations: {}
)
}
),
a!columnLayout(
contents: {
a!dropdownField(
choiceLabels: local!cityname,
choiceValues: local!cityname,
label: "Cities",
labelPosition: "ABOVE",
placeholder: "--- Select a Value ---",
value: ri!cityName,
saveInto: {
ri!cityName,

},
searchDisplay: "AUTO",
validations: {}
)
}
),
a!columnLayout(
contents: {
a!dropdownField(
choiceLabels: local!towname,
choiceValues: local!towname,
label: "Towns",
labelPosition: "ABOVE",
placeholder: "--- Select a Value ---",
value: ri!townName,
saveInto: {ri!townName},
searchDisplay: "AUTO",
validations: {}
)
}
)
}
)
}
)