String validation

Question

Hi , 
 
 How can we apply string data validation in the textfield in Appian. I have a requirement in which the first two alpahbets, should be either a or A and the second one will be c or C. In short for a particular string , how can i check the character value at a particular index and apply validation.

Mike Schmitt · Accepted Answer

When you have a dropdown field whose value will initially be null (so, most of the time), you need to also set a "placeholder label" value -- this is usually just text that will help the user know what to do, and shows up when the value is NULL, but doesn't count as a valid selection if the field is required. Setting this correctly will cause your error message to go away. 
 e.g. 
 
 a!localVariables(
 local!year,
 a!dropdownField(
 choiceLabels: {
 "2020",
 "2021",
 "2022"
 },
 choiceValues: {
 "2020",
 "2021",
 "2022"
 },
 value: local!year,
 saveInto: local!year,
 placeholderLabel: "--Select Year--"
 )
) 
 (also, i fixed the choiceLabels and choiceValues - these should be arrays, the way you had them they were just strings that would cause them to only show up as one option instead of three)

Peter Lewis · Answer

So when you set up a validation in Appian, the result of the validations parameter should either be some text (which is what will display as the error message) or null. If a text is returned, Appian assumes that a validation should be triggered, while null means no validation should show. If you want to use the expression above, you will probably need something like this: 
 a!textField(
 value: ri!monthEndCDT.monthendkey,
 saveInto: {
 ri!monthEndCDT.monthendkey
 },
 validations: if(
 and(
 like(
 ri!monthEndCDT.monthendkey,
 "[0-9][0-9]/[0-9][0-9][0-9][0-9]"
 ),
 len(ri!monthEndCDT.monthendkey<7)
 ),
 null,
 "enter valid date Value MM/YYYY"
 )
) 
 That being said, I still wouldn't recommend using a text field for this - two dropdowns would probably work a lot better and be more clear for the user.

Mike Schmitt · Answer

In general for dates, the text function is really only useful if the value you're starting with is an actual date value - i.e. " text(now(), "mmm/yyyy") " would work well, but i don't know if it would work very well with inputs that aren't a date value or something corresponding to this.

Peter Lewis · Answer

There's two things going on here. First is the representation of a date value as a number. If you ever try to convert a date to an integer, the number represents the number of days before or after 1 January 2035 (see the todate() function docs for more information). So in the case you gave above, 38353 is considered that many days after 1 Jan 2035, which results in 3 Jan 2140. 
 The second thing to consider is the method Appian uses to display dates using the text function. The text function can display many kinds of date formats depending on what format is provided as the second parameter. For example, the following options all display some kind of month: 
 
 "m" --> returns the month number without leading zeros; for example, January would be 1 and November would be 11 
 "mm" --> returns the month number with leading zeroes; for example, January would be 01 and November would be 11 
 "mmm" --> returns the three letter name of a month; for example January would be Jan and November would be Nov 
 "mmmm" --> returns the full month name 
 
 All that being said, this function is used to go from a number to a string, but I believe you want the opposite (go from the text month name to a number). The best way to do this is to use choiceValues to save the number for month instead of the text name like this: 
 a!localVariables(
 local!month,
 a!dropdownField(
 choiceLabels: {
 "Jan",
 "Feb",
 "Mar"
 },
 choiceValues: {
 "01",
 "02",
 "03"
 },
 value: local!month,
 saveInto: local!month,
 placeholderLabel: "--Select Month--"
 )
)

Mike Schmitt · Answer

Why not use an Appian Date field to capture a date type value, then extract the month and year from that? This would keep you from having to use a lot of extra custom validation. 
 Doing this using text would be possible, but it would be frustrating and complicated. Perhaps less complicated if you have the regex plugin and you're already pretty familiar with how to use regex.

Peter Lewis · Answer

Could you also use dropdown fields to limit their options? If you provide a dropdown for month and year right next to each other, a validation wouldn't be necessary because you would only display months and years that are valid.

shwetad7106 · Answer

Hi ST07 , you can use function charat(text,index) to perform this validation.

Mike Schmitt · Answer

In addition to charat() , you might also check out the function left() ; left("aces", 2) would result "ac", which should satisfy your use case. I'll post a more expansive code sample here, just to be thorough: 
 a!textField(
 label: "My Text",
 value: ri!textInput,
 saveInto: ri!textInput,
 validations: {
 if(
 upper(left(ri!textInput, 2)) = "AC",
 null(),
 "Text must begin with the string 'AC' (case insensitive)."
 )
 }
)

String validation

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