Using "with" Blocks: Any Problem?

Question

Is the use of with blocks frowned upon among InDesign scripters these days? I'm aware that they are often disfavored in the web world, but I see them used in some sample code I've seen, and being analogous to AppleScript tell blocks, it seems to cut out a lot of repetition or creating non-essential variables. Is there really a risk? Some of the reasoning I've seem mentioned to avoid it involve scoping of variables with the same name, but that could easily be avoided in a personal script, no?

Answer 1

Hi Rc
In my opinion there are 2 issues regarding the use of with.
1) General issues which are the sources of the frowns and the reason why ECMA V5 strict mode bans it use see with - JavaScript | MDN I can not see why those reasons should not apply to Indesign.
2) Specific InDesign issues.
A quick intro for the wider audience.
With can be as far as I know used in 3 ways 1) Method, 2) Property Set 3) Property Get.
The following 2 scripts show how we can apply these 3 ways using and not using with,
// With With
var myRec = app.activeDocument.rectangles[0]; // Note script will crash here if you don't use your brains
var s;
with (myRec) {
    move ([],[10,30]); // method
    rotationAngle = 45; // property set
    shearAngle = 15; // property set
    strokeWeight = 3;// property set
    fillColor = app.activeDocument.colors.itemByName("Cyan");// property set
    strokeColor = app.activeDocument.colors.itemByName("Magenta");// property set
    s = shearAngle;// property Get
// Without With
var myRec = app.activeDocument.rectangles[0]; // Note script will crash here if you don't use your brains
var s;
myRec.move ([],[10,10]); // method
myRec.properties = {
    rotationAngle: 45,// property set
    shearAngle: 15, // property set
    strokeWeight: 3,// property set
    fillColor: app.activeDocument.colors.itemByName("Cyan"),// property set
    strokeColor: app.activeDocument.colors.itemByName("Magenta"),// property set
s = myRec.shearAngle // property get
If you run both script you might think there's not much in it.
Regarding the "method" and "get" usages besides the general "with" issues then I don't think there's much of a difference.
However regarding the "set" usage there can be a very significant difference.  You can see this by running each script and undo the changes made to your rectangle by each script.
Using with you have to undo each and every property setting as each one is applied in turn.
Using properties all the properties are set at the same time and only one undo is needed. (Each property setting can result in a document redraw and a disk writing.
Setting the properties in one go can have a very large difference to the run time of the script.  Although one can reduce this by using redraw = false and FAST_ENTIRE_UNDOMODE using these can sometime be problematic.
However even when scripting Illustrator and the like where one cannot set properties on mass the general issues apply.
My pennies worth,
Trevor