# A Tour of Cycstub¶

This section will walk through the source files of the stub archetypes in Cycstub. Cycstub provides three stub archetypes:

• StubFacility
• StubInstitution
• StubRegion

We will walk through StubFacility’s source specifically because its the most complicated of the three. Before we begin, though, let’s get a fresh copy of Cycstub (or follow along on the website).

Getting cycstub via git:

$git clone https://github.com/cyclus/cycstub.git$ cd cycstub


Getting cycstub via zip:

$curl -L https://api.github.com/repos/cyclus/cycstub/zipball > cycstub.zip$ unzip cycstub.zip
$mv cyclus-cycstub-* cycstub$ cd cycstub


Feel free to rm the cycstub directory when we’re done (you can always get it back!).

## StubFacility¶

The StubFacility provides the minimal interface that an archetype that derives from cyclus::Facility must provide. We’ll go through both the header (h) and implementation (cc) files in conjunction, starting at the top.

stub_facility.h has a single Cyclus-based include

#include "cyclus.h"


which includes most cyclus kernel headers as a convenience for new archetype developers. You’re more than welcome to include the specific kernel headers you need if you require a smaller executable.

Moving on in the header file we come to the class declaration

class StubFacility : public cyclus::Facility  {


which simply states that the StubFacility inherits from cyclus::Facility.

We then come to the constructor declaration

explicit StubFacility(cyclus::Context* ctx);


and implementation

StubFacility::StubFacility(cyclus::Context* ctx)
: cyclus::Facility(ctx) {};


The constructor takes a single cyclus::Context argument. The context is the mechanism by which agents can query and otherwise communicate with the simulation environment. Because the base cyclus::Agent class requires a cyclus::Context argument in its constructor, all derived classes must pass the argument down its constructor chain, as StubFacility does with its cyclus::Facility constructor above.

Continuing with the header file, we next come to the prime directive

#pragma cyclus


In short, the prime directive allows an archetype developer to use the Cyclus preprocessor to autogenerate many member functions that are required for Cyclus features related to initialization and restart capabilities. For a further explanation, see Using the Cyclus Preprocessor.

The next line in stub_facility.h is also related to the preprocessor’s ability to help automate some documentation:

#pragma cyclus note {"doc": "A stub facility is provided as a skeleton " \
"for the design of new facility agents."}


Again, #pragma cyclus note is explained further in Using the Cyclus Preprocessor.

Continuing along, we reach the final three member functions, each of which are defined on the base cyclus::Agent class and are overrode by the StubFacility.

### str¶

The declaration

virtual std::string str();


and implementation

std::string StubFacility::str() {
return Facility::str();
}


of the str method allows the StubFacility to customize its string representation, which is printed at a variety of cyclus::Logger logging levels, which is explained further in Logging.

### Tick¶

The declaration

virtual void Tick();


and implementation

void StubFacility::Tick() {}


of the Tick member function allows the StubFacility to act during the tick agent phase.

### Tock¶

The declaration

virtual void Tock();


and implementation

void StubFacility::Tock() {}


of the Tock member function allows the StubFacility to act during the tock agent phase.