Do not allow whitespace only in textfield validation

Question

I have a textField that I do not want users to be able to enter in a space unless it is a part of the case number. 
 For example, users should not be able to enter this: 
 
 But if there are spaces in the case number, then it should be allowed

I've tried regexmatch, I've tried a if / isnullorempty statement 
 example: 
 if(
 a!isNullOrEmpty(ri!notice),
 "Case Number is invalid.",
 null()
)

Mike Schmitt · Answer

trim your input at save time. 
 a!textField(
 label: "notice",
 value: ri!notice,
 saveInto: a!save(ri!notice, trim(save!value))
)

Mike Schmitt · Answer

You can only display an error message when a string is entered. So you can choose either to trim the input (thus not allowing only blank space to be entered), or you can use a validation that shows up when removing all blanks would result in a null. 
 validations: { if( a!isNullOrEmpty(trim(ri!notice)), "don't enter only blank spaces", null() ) }