Trouble-shooting Tip For Angular Directives (Or, Learning To Love Hyphens All Over Again)

I have a couple of apps that make $http.get() calls and I wanted to be able to show a nicely formatted error message with ugly error details hidden, but accessible.  Basically, this:


And then if the user clicks on the error, they see more info:


Simple stuff.  Since the exact same potential error can appear in the administrative screen as well as the end user screen, it clearly called for a custom Angular directive.  I  found this outstanding series of articles ( by the great Dan Wahlin.  Following his advice, I very quickly created a <hello-world> directive and moved on to my more complex error display squeegee. I ran into a bit of trouble with this more complex directive.  Happily, sort of by chance, I had told WebStorm (the editor I use these days) that the JS file was an Angular file and it helped me figure out the issue.  This is the code for the directive itself:

angular.module("CDLApp").directive("generalCdlErrorHandler", function() {

return {
restrict: "E",
replace: true,

scope: {
retrieveLastConfigurationError: "&"

'<div class="alert alert-danger" role="alert" ng-init="doShowExpandedErrorDetails = true" ng-show="retrieveLastConfigurationError()">' +
' There was an I/O error or other error. This usually happens because configuration data file could not be ' +
' found or the configuration file contains inaccurate information (such as referencing a document library ' +
' that does not exist).' +
' <br/>' +
' <div ng-show="doShowExpandedErrorDetails">' +
' <a href="#" ng-click="doShowExpandedErrorDetails = ! doShowExpandedErrorDetails">' +
' Click here to hide details.' +
' </a>: ' +
' <br/>' +
' <pre>{{retrieveLastConfigurationError() | json}}</pre>' +
' <br/>' +
' </div>' +
' <div ng-show="!doShowExpandedErrorDetails">' +
' <a href="#" ng-click="doShowExpandedErrorDetails = ! doShowExpandedErrorDetails">' +
' Click here to expand error details.' +
' </a>' +
' </div>' +

Basically, I’m creating a new element called a “generalCdlErrorHandler”.  It needs access to a function called retrieveLastConfigurationError and that’s handled in the scope object.  I probably could have just used the parent’s scope, but that feels lazy.  If anyone thinks I should have done that, I’d love to hear about it in the comments.

This was all fine, but I wasn’t getting anything.  No errors popped up in the console (at least once I fixed all the sx errors I created along the way).  I simply didn’t get any output from the directive.  I went and added some static text before the ng-show directive and I *did* get that. This made me think that perhaps the directive wasn’t allowed to implicitly create new vars like “doShowExpandedErrorDetails” or have an “ng-init” in there. 

I went back into the HTML to see if I had a type and this time WebStorm helped me out.  I had been passing in the retrieveLastConfigurationError function like this:

<general-cdl-error-handler retrieveLastConfigurationError="CDLController.retrieveLastConfigurationError()">

But it really needed to be this:

<general-cdl-error-handler retrieve-last-configuration-error="CDLController.retrieveLastConfigurationError()">

WebStorm was smart enough to know that it had to be hyphenated.  If it hadn’t provided that hint, I’d probably be still troubleshooting this Smile.  Fun times!

The trick is this: not only is the directive element name hyphenated, so are any attributes you add to it.  Once I added the hyphens, it all worked great.  Dan’s tutorial happened to use short single names, so I didn’t make the connection.

Hope this helps someone.


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