Code Quality Improvement - Session 62: Two Hair-Raising Cases

To prevent runtime errors that occur when close is called again on an already-released resource in a resource management class, the function should be designed to be idempotent. Idempotency refers to the property where calling a function once or multiple times produces the same result.

Implementing a function to be idempotent offers the following benefits.

• No separate state check is needed before calling the function
• The state after calling the function can be easily predicted
• The initial state can be encapsulated and hidden

This concept can also be applied to cyclic state transitions (e.g., the run/stop state of an Animation class). By designing the function to do nothing if the state is already the target state, the final state can be stably maintained even when multiple event handlers are called simultaneously.

Also, in systems with three or more states, complex state transitions can be simplified by designing certain states to take priority. For example, in a Task class, designing the finish call to take priority over the start call makes state management more robust.