Principles

Simulation is based on steps. Each step is made by calling method step of any simulator. You can set behavior of what happens with each step by calling methods in stepping protocol (methods category). You can make single step by calling method step, or you can start repeating steps, called run, by calling methods stating with repeat, like repeatWithDelay:.

When DCSimulationGUI gets controller, it opens itself as window and created DCDiagramSimulator, which creates structure of all its elements. Then it saves status of model by calling saveState. You can reload status from last calling of saveState by calling loadState.

Running stops and loadState is called when you close simulation GUI or change structure of model (add or remove element). When loadState is called, running also stops.