Retrieve object by Mx GUID

At a project the company uses Mendix to take track of the reviewing process of reports. At a sertain day in the month Mendix will create an object ReportPerformance which contains the information of the report that will be build by a MS solution and will be placed in a DataWareHouse. In this DWH the report and the report in the MX App will be related by the Mx GUID. Now after publishing the report in the DWH the MS solution will push a message to a webservice in the Mendix App that will trigger a microflow which retrieve the ReportPerformance object and change the object by two attributes (both Strings). Now I've found this article: which shows how to use the ID in xpath, but I get the following error: required(...)+loop did not match anything at input 'id' as I use the statement in the article of the reference guide: id($ID) when I use [id = $ID] I get the following error: Incomaptible expression types: Report.ReportPerformance, String. even when I use a integer or float. Can somebody please help me with this case because the client hopes to use the webservice before friday. Is there a solution that the Input Parameter of the Microflow is of type Object ReportPerformance and that I try to retrieve a object ReportPerformance that is the same as the ID that the webservice gives to me by string? (so input parameter: object ReportPerformance, in the mf I do a retrieve of object ReportPerformance where the xpath is id = inputReportPerformance, and at the call of the webservice the other software send me just an ID by String format?)
1 answers

Maybe use your own unique identifier attribute and retrieve data on that attribute. You decide the type (string, integer) and do necessary conversions before retrieving.