Some external procedures must be configured at initialization time. This initialization takes one of two forms, depending on the type of the external procedure:
Initialization of Informatica-style external procedures.
The Tx<MODNAME> class, which contains the external procedure, also contains the initialization function, Tx<MODNAME>::InitDerived. The signature of this initialization function is well-known to the Integration Service and consists of three parameters:
nInitProps.
This parameter tells the initialization function how many initialization properties are being passed to it.
Properties.
This parameter is an array of nInitProp strings representing the names of the initialization properties.
Values.
This parameter is an array of nInitProp strings representing the values of the initialization properties.
The Integration Service first calls the Init() function in the base class. When the Init() function successfully completes, the base class calls the Tx<MODNAME>::InitDerived() function.
The Integration Service creates the Tx<MODNAME> object and then calls the initialization function. It is the responsibility of the external procedure developer to supply that part of the Tx<MODNAME>::InitDerived() function that interprets the initialization properties and uses them to initialize the external procedure. Once the object is created and initialized, the Integration Service can call the external procedure on the object for each row.
Initialization of COM-style external procedures.
The object that contains the external procedure (or EP object) does not contain an initialization function. Instead, another object (the CF object) serves as a class factory for the EP object. The CF object has a method that can create an EP object.
The signature of the CF object method is determined from its type library. The Integration Service creates the CF object, and then calls the method on it to create the EP object, passing this method whatever parameters are required. This requires that the signature of the method consist of a set of input parameters, whose types can be determined from the type library, followed by a single output parameter that is an IUnknown** or an IDispatch** or a VARIANT* pointing to an IUnknown* or IDispatch*.
The input parameters hold the values required to initialize the EP object and the output parameter receives the initialized object. The output parameter can have either the [out] or the [out, retval] attributes. That is, the initialized object can be returned either as an output parameter or as the return value of the method. The datatypes supported for the input parameters are:
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