C Language – Design Patterns and Object-Oriented Design (C3)

Course content:

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• Clear, maintainable code written for humans
1. Use established practices and design patterns
2. Describe software as components and behaviors
3. Separate behavior from implementation details

• Object-oriented software design
1. Program composed of cooperating components
2. Components have assigned responsibilities
3. Think about each component’s role and purpose

• Introducing object-oriented programming
1. Virtual methods via function pointers
2. Abstract interfaces using operations structs
3. Object-oriented architecture

• Differences from object-oriented languages
1. Large amounts of boilerplate code
2. Casting without strict type checks
3. Imitating inheritance with base functions

• Alternatives for implementing OOP
1. Function pointers stored directly with data
2. Rust-like architectures and fat pointers
3. Static polymorphism via linking

• Dependencies between components
1. Pointers and ownership
2. Responsibility for object destruction
3. Removing memory leaks

• Principles of good software design
1. Component independence and localized changes (SRP)
2. Depend on interfaces, not implementations (DIP)
3. Keep code closed to modification when extending (OCP)

• Changing component behavior at runtime
1. State machine and the State pattern
2. Implementation with switch and enums
3. Differences from a pure state machine

• Bridging interfaces using structural patterns
1. Separate different domains (Bridge)
2. Bridge mismatched interfaces (Adapter)
3. Expose a simplified interface (Facade)

• Chaining via a single interface
1. Add behavior to existing systems (Decorator)
2. Chain possible handlers (Chain of Responsibility)
3. Control and mediate access to objects (Proxy)

• Linear data structures and sequences
1. Traversing structures (Iterator)
2. Distinguish linked list and chain structures
3. Terminate without null pointers (Null Object)

• Composing complex objects and components
1. Branch by concrete type (Visitor)
2. Tree structure of objects (Composite)
3. Solutions using union and switch combinations

• Creating diverse object types
1. Factory for all kinds of objects (Factory)
2. Abstract factory for object families (Abstract Factory)
3. Use function pointer for type registration

• Objects with a single instance
1. Create a single instance on first use (Singleton)
2. Manage global resources
3. Stateful communication with the OS

• Multi-step object construction
1. Builder object as an intermediate step (Builder)
2. Methods to modify the builder and finalize build
3. Split the builder into multiple phases

• Signaling and event handling
1. Central coordinating component (Mediator)
2. Register event subscribers (Observer)
3. Signals with function pointer callbacks (signals & slots)

• Generation, streaming and lazy evaluation
1. Process sequences and pipelining (iterators)
2. Use message queues
3. Generate state machines without callbacks

• Representing data changes
1. Describe a concrete change (transaction, command)
2. Sequence of subsequent changes (journal)
3. Use mini-language or bytecode (interpreter)

• Persisting and restoring state
1. Create snapshots of state data (snapshot, memento)
2. Handle history of snapshots (history, recovery)
3. Combine snapshots and transactions (incremental backup)

• Optimizing data handling
1. Data structures with instant snapshots (copy-on-write)
2. Share mostly immutable parameters (flyweight)
3. Clone objects and the "rule of zero" (clone, prototype)