InDesign CC 2017 ExtendScript - Can't overwrite text in TextArea - adobe-indesign

Question

At this point, I'm sure this is something simple that I'm missing but I can't for the life of me figure it out.
Working on an InDesign script that takes text passed into the script and writes it into the currently selected text area.
insertButton.onClick = function(){
var postIndex = postList.selection.index;
var postContent = posts[postIndex].content.rendered;
$.writeln(app.selection[0].parentStory.contents);
app.selection[0].parentStory.contents = postContent;
$.writeln(app.selection[0].parentStory.contents);
myWindow.close();
}
I've confirmed that the function is getting called correctly, that postContent exists and is what I expect it to be and that the first writeln call dumps out the current value of the TextArea. The second $.writeln never fires, so I know the error is on
app.selection[0].parentStory.contents = postContent;
Is there an updated way to set TextArea contents that I haven't found in documentation?
Thanks in advance!

Answer 1

I think your problem is that your window is modal thus preventing any interaction with inDesign objects.
You have to quit the dialog first in order to modify objects:
var w = new Window('dialog');
var btn = w.add('button');
btn.onClick = function() {
w.close(1);
}
if ( w.show()==1){
//"InDesign is no longer in modal state. So you can modify objects…")
}

Answer 2

...postContent exists and is what I expect it to be...
Indesign expects a string here --> is it what you expect as well?
What is an input selection? text? textFrame?
You could
alert(postContent.construction.name)
to ensure what you've got
Jarek

Answer 3

When debugging was enabled in ExtendScript Toolkit, I was able to find the error being thrown:
"cannot handle the request because a modal dialog or alert is active"
This was referring to the dialog I opened when I initiated the script.
Delaying the text insertion until the dialog has actually been closed fixed the issue.
insertButton.onClick = function(){
var postIndex = postList.selection.index;
postContent = posts[postIndex].content.rendered;
postContent = sanitizePostContent(postContent);
// The 1 here is the result that tells our code down below that
// the window has been closed by clicking the 'Insert' button
myWindow.close(1);
}
var result = myWindow.show();
// If the window has been closed by the insert button, insert the content
if (result == 1) {
app.selection[0].parentStory.contents = postContent;
}