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CustomWrappers and base view Interpolation variables

Hello, We are in the process of creating a custom data source for one of our internal sources. It takes two CustomWrapperInputParameters, both mandatory strings. ``` public CustomWrapperInputParameter[] getInputParameters() { return new CustomWrapperInputParameter[] { new CustomWrapperInputParameter(PARAMETER_A, "Parameter A", true, false, CustomWrapperInputParameterTypeFactory.stringType()), new CustomWrapperInputParameter(PARAMETER_B, "Parameter B", true, false, CustomWrapperInputParameterTypeFactory.stringType()) }; } ``` When creating a base view on that wrapper, and specifying a value for both parameters, then we obtain data successfully. When creating a base view on that wrapper, and using interpolation variables for both parameters, then the input parameters are passed as null, even though values are passed in the base view. Does this sound like a familiar issue ?
user
15-03-2021 06:47:13 -0400
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1 Answer

Hi, In general, when an interpolation variable is passed during creation of base view it should be prefixed with a **‘@’**. So during execution of the base view created with interpolation, the value for the interpolation variable can be provided. If the base view is producing null results, I would check if the interpolation value is escaped correctly. For instance when providing email as an interpolation variable with domain name as constant I would specify it as follows: **Email = @EMAIL_NAME\@mail.com **, with **@EMAIL_NAME** as the interpolation variable. Also I would check the execution trace to see if the value is correctly being filtered to the source. You can take a look at the [Using Interpolation Variables as Custom Sources’ Input Parameters](https://community.denodo.com/docs/html/browse/latest/en/vdp/administration/creating_data_sources_and_base_views/custom_sources/custom_sources#using-interpolation-variables-as-custom-sources-input-parameters) section of the Virtual DataPort Administration Guide for more information. Hope this helps!
Denodo Team
16-03-2021 08:36:00 -0400
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