How to force selection of a specific answer in a dropdown field within an editable grid

Question

Hi team 
 I'm needing some help to force an answer in a dropdown field where a given answer is selected in another dropdown field. 
 Here is a screenshot of the editable grid. 
 I want to force "not used" in the "how important" column when "never" is selected in the "how often" column 
 
 The software names are returned from an existing table. 
 This is how the answer table is set up:

Answer Table

id 
 Name 
 questionID

1 
 Daily 
 1

2 
 Weekly 
 1

3 
 Monthly 
 1

4 
 Quarterly 
 1

5 
 Annually 
 1

6 
 Never 
 1

7 
 Vital 
 2

8 
 Important 
 2

9 
 Useful 
 2

10 
 Not Useful 
 2

11 
 Not Used 
 2

The questionId corresponds to the two column headings. 
 Here's the expression for teh editable grid: 
 { /* For the Software Title Column*/ a!richTextDisplayField( value: a!richTextItem( text: fv!item.softwareID.name, color: "ACCENT", size: "MEDIUM", style: "STRONG" ) ), /* For the Frequency Of Use and Vitality Columns*/ a!forEach( items: fv!item.surveyResultUserResponse, expression: a!dropdownField( placeholder: "Select", choiceLabels: fv!item.question.allowedAnswer.name, choiceValues: fv!item.question.allowedAnswer.name, value: fv!item.answer, saveInto: { fv!item.answer }, required: true ) ) 
 I'm stumped! 
 I would greatly appreciate answers with sample expressions, please 
 Thanks 
 Stephen

Mike Schmitt · Answer

When you say "force 'not used'", what exactly are you hoping the sequence of events the users sees will be? 
 It would be trivially easy, for example, to set that dropdown to "required" and add a validation such that the only valid answer is "not used" when the selection in the previous column is "never".

Chris · Answer

I typically implement this by first having the "How Often" dropdown perform an a!save() to update the neighboring "How Vital" column, setting it to Not Used when Never is selected, then have the How Vital column become disabled in the same scenario. You could take this further and prevent "Not Used" from being selected with validation when any other selection of How Often is selected, or have the How Often selection simply clear the How Vital selection whenever it is toggled otherwise, etc. 
 Essentially, you can easily reference data points across the row when you need to check other values: 
 a!localVariables(
 local!howOften: {"Daily","Weekly","Monthly","Quarterly","Never"},
 local!howVital: {"Vital","Important","Useful","Not Useful","Not Used"},
 local!data: {
 a!forEach(
 items: 1+enumerate(4),
 expression: a!map(id: fv!item, software: concat("Antivirus ",fv!item), howOften: null, howVital: null)
 )
 },
 a!gridLayout(
 headerCells: {
 a!forEach(
 items: {"Software","How often do you use this?","How vital is this to your work?"},
 expression: a!gridLayoutHeaderCell(label: fv!item)
 )
 },
 rows: a!forEach(
 items: local!data,
 expression: a!gridRowLayout(
 id: fv!index,
 contents: {
 a!richTextDisplayField(
 value: a!richTextItem(
 text: fv!item.software
 )
 ),
 a!dropdownField(
 placeholder: "-- Select --",
 choiceLabels: local!howOften,
 choiceValues: local!howOften,
 value: fv!item.howOften,
 saveInto: {
 local!data[fv!index].howOften,
 if(
 local!data[fv!index].howOften="Never",
 a!save(local!data[fv!index].howVital,"Not Used"),
 {}
 )
 }
 ),
 a!dropdownField(
 placeholder: "-- Select --",
 choiceLabels: local!howVital,
 choiceValues: local!howVital,
 value: fv!item.howVital,
 saveInto: local!data[fv!index].howVital,
 disabled: local!data[fv!index].howOften="Never",
 )
 }
 )
 )
 )
)