Error message: Expression evaluation error at function 'tointeger' param

What is the datatype of data_array? Are you trying to subtract a date from an array of dates?

@shaoyongw - This error comes only when data_array is {} as this represents a object with no data type associated with it. You may have to type cast to date and then use it.

For e.g - tointeger(todate({})-today()) will return some result.

and tointeger({}-today()) - gives error as you mentioned.

What kind of result do you expect from this rule when data_array is empty? I will probably do a thing like this if (rule!APN_isEmpty(data_array),{},tointeger(data_array-today()))

@shaoyongw As explained above by other practitioners, you may need to depend on type casting where you may use Conversion Function todate() or you may also use typeof() in combination with cast() on the data_array.

Just in case, if the data_array is an output of the queryEntity, I would suggest converting the queried data to the desired custom data type as that eliminates the usage of conversion functions on individual columns in the CDT which is not a great idea.