Decorating angular exceptionHandler service in Typescript using VS 2013 - angularjs

Question

Using Typescript and Visual Studio 2013
I want to decorate the angularjs $exceptionHandler and I'm not quite sure of the correct way to do it. I have decorated $log and it works fine.
My configuration:
MyAngularModule.config(['$provide',($provide) => {
$provide.decorator('$log', ['$delegate', function ($delegate) {
var myLog: MyLogService.LogService = new MyLogService.LogService();
return myLog;
}]);
}]);
MyLogService.ts
export = Example;
module Example {
export class LogService implements ng.ILogService{
constructor() {}
public assertEmpty = () => { };
public reset = () => { };
public info: ng.ILogCall = ...all my code...
}
}
Now when I try doing a similar thing with $exceptionHandler:
$provide.decorator('$log', ['$delegate', function ($delegate) {
var myExHandler: MyExHandler.ExHandlerService = new MyExHandler.ExHandlerService();
return myExHandler;
}]);
The interface definition for exceptionHandler in the type files is:
interface IExceptionHandlerService {
(exception: Error, cause?: string): void;
}
How do I code this similar to the way I did in decorating the log service?
I tried:
export = Example;
module Example {
export class ExHandlerService implements ng.IExceptionHandlerService{
constructor(anException: Error, aCause?: string) {}
}
}
And Visual Studio is complaining that the interface is implemented wrong. I don't really understand what (exception: Error, cause?: string): void; means, is it the constructor? The typings file does show a name, just this anonymous method definition.
I don't understand how I even approach this in the decorate call (ie. where do the error and cause parameters come from and how do I keep the default implementation operating as well?)
Thanks in advance.
Update:
Considering in angular.d.ts:
interface IExceptionHandlerService {
(exception: Error, cause?: string): void;
}
I guess my root confusion is how this interface would be implemented in Typescript??
Ok, I found that interfaces can define a function type in this case. That created confusion with the way I have viewed interfaces typically. It seems I can't use an "implements" in this case?

Answer 1

I think I've found my own answer. In any case here is how I decorated the angular exception handler service in Typescript.
export class MyExceptionHandlerService {
private _defaultExceptionHandlerService: ng.IExceptionHandlerService;
constructor(paramDelegate: ng.IExceptionHandlerService) {
this._defaultExceptionHandlerService = paramDelegate;
}
public exception: ng.IExceptionHandlerService = (paramException: Error, paramCause?: string): void => {
console.error("MY ERROR HANDLER: " + paramException.message)
this._defaultExceptionHandlerService(paramException, paramCause);
}
}
And I use it from my angular config section like this:
$provide.decorator('$exceptionHandler', ['$delegate', function ($delegate: ng.IExceptionHandlerService) {
var localExceptionHandler: MyHandler.ExceptionHandlerService = new MyHandler.ExceptionHandlerService($delegate);
return localExceptionHandler.exception;
}]);
It's working as expected for me.

Answer 2

You could have also done something like this without using objects...not sure if this is good or not. Feedback would be awesome!
((): void => {
'use strict';
angular
.module('app.blocks')
.config(config);
config.$inject = ['$provide'];
function config($provide: ng.auto.IProvideService): void {
$provide.decorator('$exceptionHandler', extendExceptionHandler);
}
extendExceptionHandler.$inject = ['$delegate', 'app.blocks.logger'];
function extendExceptionHandler(
$delegate: any,
logger: app.blocks.ILogFactory): Function {
return (exception: Error, cause?: string, source? : string) => {
$delegate(exception, cause);
logger.log(exception.message, { exception: exception, cause: cause }, source, 'error');
}
}
})();