Eclipse Community Forums: Epsilon

Help

Home

Home » Modeling » Epsilon » Using reflection

Show: Today's Messages :: Show Polls :: Message Navigator

Using reflection [message #1820543]

Wed, 22 January 2020 13:48

Ludovico Iovino

Messages: 33
Registered: July 2019

Member

Hi all. I was wondering if there is a way to call a user defined operation in EOL with a sort of reflection style ...for instance by name.

This means that if I have an operation in my eol file called :

getPersons() on a specific context, i would like to call it by operation name. this is because I have this info in my models. Is it possible ?

Report message to a moderator

Re: Using reflection [message #1820550 is a reply to message #1820543]

Wed, 22 January 2020 15:45

Sina Madani

Messages: 160
Registered: November 2015
Location: York, UK

Senior Member

Hi Ludovico,

To my knowledge this is not possible, however I'm not sure why you would need this. There are two workarounds I can think of. The first is to generate your EOL program using EGL/EGX for a given model. Basically you paste your EOL code into an EGL template and use dynamic sections to retrieve and output the operation call. Another is to define helper methods which call the desired operation based on the model. For example, if the operation you want to call is defined in your model, you could have an operation with a "switch" statement on the model element property which defines this method and call it like that.

operation Any callOperation(operationName : String) {
    switch (operationName) {
        case "foo": return self.foo();
        case "bar": return self.bar();
        case "baz": return self.baz();
        default: throw "Unknown operation '"+operationName+"'";
    }
}

Report message to a moderator

Re: Using reflection [message #1820551 is a reply to message #1820550]

Wed, 22 January 2020 15:50

Ludovico Iovino

Messages: 33
Registered: July 2019

Member

Thanks Sina, actually the first solution is how I have already implemented, but I thought I could further automate the process. Thanks for confirming it.

Report message to a moderator

Re: Using reflection [message #1820562 is a reply to message #1820551]

Wed, 22 January 2020 21:32

Dimitris Kolovos

Messages: 2165
Registered: July 2009
Location: York, UK

Senior Member

Hi Ludovico,

Below is a terrible solution for calling operations reflectively.

var s = "";

s.call("foo").println();
s.call("bar").println();

operation String foo() : String {
	return "foo";
}

operation String bar() : String {
	return "bar";
}

operation Any call(op : String) : Any {
	var m = new Native("org.eclipse.epsilon.eol.EolModule");
	m.parse("return target." + op + "();");
	m.operations.addAll(System.context.module.operations);
	m.context.frameStack.put("target", self);
	return m.execute();
}

Cheers,
Dimitris

Report message to a moderator

Re: Using reflection [message #1820563 is a reply to message #1820562]

Wed, 22 January 2020 21:41

Dimitris Kolovos

Messages: 2165
Registered: July 2009
Location: York, UK

Senior Member

... and below is a more decent solution.

var s = "";

s.call("foo").println();
s.call("bar").println();

operation String foo() : String {
	return "foo";
}

operation String bar() : String {
	return "bar";
}

operation Any call(op : String) : Any {
	return System.context.module.
		operations.selectOne(o|o.name = op).
		execute(self, /*parameters*/ Sequence{}, System.context);
}

Cheers,
Dimitris

Report message to a moderator

Re: Using reflection [message #1820587 is a reply to message #1820563]

Thu, 23 January 2020 14:03

Sina Madani

Messages: 160
Registered: November 2015
Location: York, UK

Senior Member

I suppose we could also add this logic to the end of OperationCallExpression.execute. For example the following seems to work:

if (module instanceof IEolModule &&
    "call".equals(operationName) &&
     parameterValuesArray.length > 0 &&
     parameterValuesArray[0] instanceof String) {
		String reflectiveOpName = (String) parameterValuesArray[0];
		Operation refOp = ((IEolModule) module).getOperations().stream()
			.filter(op -> reflectiveOpName.equals(op.getName()))
			.findAny()
			.orElse(null);
		
		if (refOp != null) {
			return refOp.execute(targetObject, parameterValues.subList(1, parameterValues.size()), context);
		}
}

and in EOL:

call("foo").println();

operation String foo() {
	return "foo called";
}

Report message to a moderator

Re: Using reflection [message #1820657 is a reply to message #1820587]

Sat, 25 January 2020 09:29

Dimitris Kolovos

Messages: 2165
Registered: July 2009
Location: York, UK

Senior Member

Hi Sina,

If we want to add proper built-in support for calling operations reflectively I guess we should also check argument types, consider operation contributors, dot vs. arrow etc.

Cheers,
Dimitris

Report message to a moderator

Re: Using reflection [message #1820671 is a reply to message #1820657]

Sat, 25 January 2020 18:36

Sina Madani

Messages: 160
Registered: November 2015
Location: York, UK

Senior Member

Hi Dimitris,

That's a good point. I assume this would essentially mean calling OperationCallExpression.execute reflectively, rather than adding this minimal logic to OperationCallExpression itself, or at least factoring out the operation call logic. An alternative is to add some sort of "EOL Evaluator" built in to System, which operates on the current context's module. I'm wondering whether it is a worthwhile feature to have in the language or too niche of a requirement to support?

Thanks,
Sina

Report message to a moderator

Re: Using reflection [message #1820728 is a reply to message #1820671]

Mon, 27 January 2020 20:52

Dimitris Kolovos

Messages: 2165
Registered: July 2009
Location: York, UK

Senior Member

Hi Sina,

Given that there's a sensible workaround, I'd be inclined to wait for a couple of similar use-cases to show up before we consider implementing this feature.

Cheers,
Dimitris

Report message to a moderator