class EVariantTypeCastError with message 'Could not convert variant of type (String) into type (Double)

Question

Using Delphi and FastReport I get this error message while debugging inside Delphi immediately after this line:

.ShowReport(true)         


        

Answer 1

I got this exact same error but not with FastReport. I'll leave the context of my error, as it may help someone else. I got this error on:

RESTRequest.Execute();

I was using the TClientDataSet with TRESTResponseDataSetAdapter so that after a request to my web service the adapter would load a data set with the JSON string returned by the web service. This data set was being used to automatically check/uncheck checkboxes and load textedits and comboboxes. Since TJSONObject does not parse booleans correctly in json, I changed some checkboxes to check/uncheck based on an integer value instead of a boolean. I was then changing my webservice so that it looks for boolean columns in the datatable to an integer value 1 or 0. For some reason (my fault entirely), I was outputting a json with "" in that field instead of the integer ("1" or "0"). And this yielded that exact error. After correcting this, the error disappeared.