In a Tinderbox file that contains many persons of prototype pPerson, I have the attributes $FullName, $PreNameTitle (such as “Prof.” or “Baroness”) and $PostNameTitle (such as “MP” or “MdB”).
I want a $DisplayExpression to put these together if either fields are populated, but otherwise only give $FullName.
For that purpose, I put the following in the prototype’s $DisplayExpression attribute, expecting it to do the job:
However, I don’t get any $PostNameTitle displayed, and before the $FullName (irrespective whether the $PreNameTitle is populated) I get an unsightly double ““. Obviously there is a mistake, but no amount of tinkering has helped, so I hope someone with more insight on this forum might have a bright idea… I am using Tinderbox 11.6 if that is of any help.
The Display Expression fails for two reasons: it isn’t valid code and a Display Expression doesn’t allow multiple if() statements. The use of ? is not clear and it likely a guess made on some other coding system.
You have four possible states:
*Full name only
Prefix / full name
Full name / suffix
Prefix / full name / suffix
Using a single if() that means nesting two subsidiary if()s to get all four states. For example ( with line breaks and comments for clarity):
if(!$PreNameTitle & !$PostNameTitle){
// full name only
$FullName;
}else{
if($PreNameTitle & !$PostNameTitle){
// prefix and full name
$PreNameTitle + " " + $FullName;
}else{
if(!$PreNameTitle & $PostNameTitle){
// full name and suffix
$FullName + ", " + $PostFullName;
}else{
// prefix, full name, and suffix
$PreNameTitle + " " + $FullName + ", " + $PostFullName;
}
}
}
Messy! But in a single action we only need 3 iterative tests:
// reset the output string
$DisplayString=;
if($PreNameTitle){
// add prefix with trailing space
$DisplayString+=$PreNameTitle+" ";
};
// always add full name
$DisplayString+=$FullName;
if($PostNameTitle){
// add comma-space and suffix
$DisplayString+=", "+$PostNameTitle;
};
You could use this action in the prototype’s $Rule for quick testing, but for a real document $Edict seems a better choice:
I’ve also updated† aTbRef’s note on Display Expressions to try and clarify the point about allowing only one if() at top level (i.e. non-nested) in the expression.
Nested if()s are OK but as discussed once a Display Expression uses anything more than very simple action code, the output string for the Display Expression is better pre-compiled. The point of the latter is to avoid the $DisplayExpression action code evaluation occurring during per-note expression set-up. In a large document with complex expressions, doing that in $DisplayExpression can slow down the UI.
†. I also took the opportunity to remove some outdated suggestions that pre-date some current action code affordances.
