How to use Environment.RaiseError<T>(...)

[axefrog]

In my custom JavaScript object, I'd like to throw JavaScript errors when one or more of the arguments supplied to the constructor or to one of the member functions is invalid.

As best I can tell, I should use environment.RaiseError<T>(prototype, message).

What is the correct way to use this method and/or its overloads? I'm catching the UserError exception that is subsequently thrown, but I don't know if I'm doing it correctly because I don't know what the type argument T refers to, or what the correct way to access my error message in the thrown exception is.

[otac0n]

The raise error was made generic to fulfil F#'s requirements for the function callsites to have a certain return value.

Effectively the way it is used is like this:

public MyReturnType MyFunction()
{
    return RaiseUserError<MyReturnType>("message")
}

[axefrog]

In the wiki article, the methods are static, so there is no inherited RaiseUserError method that is available to call. There are variations on this in the Env property of FunctionObject and CommonObject, but all of them take a first argument of type CommonObject and the second argument for the error message. None of them seem to match the RaiseUserError method in your example.

[axefrog]

I apologise if you simply meant RaiseUserError where User is meant to be replaced by the appropriate method depending on the error type. It would be handy to get an understanding of which error type to use at what time. For example I want to throw an error if I was expecting an argument of type double but received NaN instead (i.e. no argument passed). Is that a range error?

[axefrog]

One more thing - if you can help me properly understand the correct way to throw errors, even when exposing a CLR method as a JavaScript global function (hence it won't have access to the Environment object), I'll write it up in the wiki for you.

[otac0n]

Methods can have access to the global Environment method, if they need it. You just need to use this as your method signature:

public TReturn MyMethod(Environment env, CommonObject @this, TArg myArgs, ...)

[fholm]

@otac0n: Unless something has been changed recently the first and second parameters should be FunctionObject and CommonObject, not Environment and CommonObject:

public BoxedValue MyMethod(FunctionObject self, CommonObject @this, BoxedValue arg1)

[fholm]

You can also access the Environment from both self and @this parameters.

[axefrog]

What about the RaiseError<T>(prototype, message) method? Is that not designed for external use? I ask because when used, the thrown exception doesn't include the specified message as part of the exception's Message property, rather the message returns [object Error]. To get the message, it looks like I have to call ((IronJS.ErrorObject)ex.Value.ClrBoxed).Members["message"], which seems a bit obtuse and probably not the right way to go about it.