Is it possible to return a complex C# type from a JavaScript function?

[dodyg]

        _engine.SetValue("condition", condition);
        _engine.SetValue("RuleResult", TypeReference.CreateTypeReference(_engine, typeof(RuleResult)));

        var script = """
function evaluate(){
    return new RuleResult(condition.Id, [], false);
}
""";

        _engine.Execute(script);
        var res = _engine.Invoke("evaluate");
        var ob = res.AsObject();

I got

    System.InvalidCastException : Object must implement IConvertible.

The type definitions for RuleResult is

public record RuleViolation(string Id, string Message);

public record RuleResult(Guid RuleInputId, List<RuleViolation> RuleViolations, bool IsOK);

[dodyg]

OK if I modify the code to become

function evaluate(){
    var ListOfRuleViolations = System.Collections.Generic.List(RuleViolation);
    var list = new ListOfRuleViolations();
    return new RuleResult(condition.Id, list, true);
}

this error System.InvalidCastException : Object must implement IConvertible. goes away. But I still can't figure out how to get the result.

[lahma]

Does it work with 3.x beta?

[dodyg]

I am using

<PackageReference Include="Jint" Version="3.0.0-beta-2051" />

var ob = res.AsObject(); works but I have to manually get the properties.

var res2 = res.AsInstance<RuleResult>(); returns null.

[lahma]

Try var ob = res.ToObject();

[dodyg]

Thanks.

    RuleResult Evaluate(MerchantInformationInput input, MerchantInformationRuleCondition condition, RuleEvaluationMode evaluationMode)
    {
        var ifShortcut = evaluationMode == RuleEvaluationMode.Shortcut;
        var violations = new List<RuleViolation>();

        _engine.SetValue("input", input);
        _engine.SetValue("condition", condition);
        _engine.SetValue("ifShortcut", ifShortcut);
        _engine.SetValue("violations", violations);
        _engine.SetValue("RuleViolation", TypeReference.CreateTypeReference(_engine, typeof(RuleViolation)));
        _engine.SetValue("RuleResult", TypeReference.CreateTypeReference(_engine, typeof(JsRuleResult)));

        var script = """
function evaluate(){
    if (condition.RequestedAmount.FromOnly && input.RequestedAmount < condition.RequestedAmount.From.Value){
        violations.Add(new RuleViolation("requested-amount-from", `RequestedAmount ${input.RequestedAmount} is less than condition RequestedAmount.From ${ condition.RequestedAmount.From }`));
        if (ifShortcut){
            return new RuleResult(condition.Id, violations, false);
        }
    }
    
    return new RuleResult(condition.Id.ToString(), violations, true);
}
""";

        _engine.Execute(script);
        var res = _engine.Invoke("evaluate");

        var ob = res.AsObject();
        var guid = ob.GetOwnProperty("RuleConditionId").Value.AsString();
        var id = Guid.Parse(guid);
        var isOk = ob.GetOwnProperty("IsOK").Value.AsBoolean();

        return new RuleResult(id, violations, isOk);
    }

This one works.

Out of curiosity, if I declare a list of T inside the script, how do I get it out?

e.g.

ob.GetOwnProperty("myList").Value.?? . What conversion method do I call?

[lahma]

Not sure about T, haven't tried it. You can probably make your code a bit cleaner by using an indexer var property = ob["foo"].AsString();