- Empty strings should not be used within calculations. A blank custom function named "Null" should be created and used for empty values (*see note below)
Within solution code this increases code readability and distinguishes literal values and escaped text from empty values.No Format Case ( If ( PatternCount ( Table::fieldName ; Tab & Tab ) ≥ 1; "Awesome use of indentation!"; Null ); If ( PatternCount ( Table::fieldName ; Tab ) ≥ 1 ; "Good code should be easy to read"; Null ); Null ) // Note the above function uses another custom function // which simply returns a tab character in order to improve // readability
good
No Format Case ( If ( PatternCount ( Table::fieldName ; " " & " " ) ≥ 1; "Awesome use of indentation!"; "" ); If ( PatternCount ( Table::fieldName ; " " ) ≥ 1 ; "Good code should be easy to read"; "" ); "" )
bad
- Here's a series of test cases for clarification - the subtle differences in FM between Null, reserved word False and "" (literal empty string):
Expression | Result | Notes |
|---|---|---|
Null | | Result is empty. |
GetAsBoolean ( Null ) | 0 | GetAsBoolean returns 0/1 for expression results. |
not Null | 1 | The boolean inverse of Null, or 1. |
Null = 0 | 0 | False: This is boolean false because FM does not evaluate empty to reserved word False (0). |
GetAsBoolean ( Null ) = 0 | 1 | True: The explicit FM boolean interpretation of Null is 0. |
GetAsBoolean ( Null ) = False | 1 | True: A different adaptation - FM reserved words True and False are evaluated to the boolean 0/1 values, so 0 = 0. |
Null = False | 0 | False: This is the most interesting case of all. Null is technically empty and False evaluates to boolean 0, so they are not equal. |
Null = "" | 1 | True: The literal empty string "" evaluates the same in FM as the empty return of Null., |
| Warning | ||
|---|---|---|
| ||
Code within a custom function can and should use double quotes for empty values "". This decreases custom function dependencies on the "null" function - making them more portable for copy-pasting. |