How to save the error message from a field validation

You can use the same expression which is used for validation to save the error messages in a rule input. You can refer the following code for more understanding:

load(
local!firstName,
local!lastName,

a!formLayout(
label: "Form",
firstColumnContents: {
a!textField(
label: "First Name",
value: local!firstName,
/* validations: if(len(local!firstName) > 10, "Number of characters in first name must be less than 10", ""), */
saveInto: {
local!firstName
}
),
a!textField(
label: "First Name",
value: local!lastName,
/* validations: if(len(local!lastName) > 10, "Number of characters in last name must be less than 10", ""), */
saveInto: {
local!lastName
}
)
},
buttons: a!buttonLayout(
          primaryButtons: {
          a!buttonWidget(
          label: "Submit",
          value: "Submit",
          saveInto: {
                     if(len(local!firstName) > 10,
a!save(ri!errors_text, append(ri!errors_text, "Number of characters in first name must be less than 10")
), {}),
           if(len(local!lastName) > 10,
a!save(ri!errors_text, append(ri!errors_text, "Number of characters in last name must be less than 10")
), {})          
          }
          )}
)
)
)

It is better to perform save operation on submit button rather than individual fields as there is a chance that user may correct himself in the first attempt itself.

Please let me know if this is not what you are looking for!

You can use the same expression which is used for validation to save the error messages in a rule input. You can refer the following code for more understanding:

load(
local!firstName,
local!lastName,

a!formLayout(
label: "Form",
firstColumnContents: {
a!textField(
label: "First Name",
value: local!firstName,
/* validations: if(len(local!firstName) > 10, "Number of characters in first name must be less than 10", ""), */
saveInto: {
local!firstName
}
),
a!textField(
label: "First Name",
value: local!lastName,
/* validations: if(len(local!lastName) > 10, "Number of characters in last name must be less than 10", ""), */
saveInto: {
local!lastName
}
)
},
buttons: a!buttonLayout(
          primaryButtons: {
          a!buttonWidget(
          label: "Submit",
          value: "Submit",
          saveInto: {
                     if(len(local!firstName) > 10,
a!save(ri!errors_text, append(ri!errors_text, "Number of characters in first name must be less than 10")
), {}),
           if(len(local!lastName) > 10,
a!save(ri!errors_text, append(ri!errors_text, "Number of characters in last name must be less than 10")
), {})          
          }
          )}
)
)
)

It is better to perform save operation on submit button rather than individual fields as there is a chance that user may correct himself in the first attempt itself.

Please let me know if this is not what you are looking for!