Code to the interface principle
A design principle in which code depends on an interface and polymorphic behavior rather than on a specific implementation or subclass.
Software Design for Python Programmers
The Code to the Interface Principle structures code to depend on a superclass interface so it can work with any compatible subclass at runtime.
- How it is used
- Structures clients around superclass interfaces so compatible subclasses can be selected and used at runtime.
- How deep it goes
- Explains interface storage, polymorphic dispatch, delegation, and runtime type checks, while cautioning against unnecessary subclass complexity.
- Examples
- Uses Book, FictionAttrs, CookbookAttrs, Catalogue, Sport, PlayerStrategy, and VenueStrategy as concrete Python examples.
- What you can do after
- Apply it via polymorphism to replace compatible implementations without changing clients that depend on their shared interface.
Read how Software Design for Python Programmers explains code to the interface principle →
Object-Oriented Software Design in C++
A design principle that makes code depend on an interface and polymorphic behavior rather than a specific subclass implementation.
- How it is used
- Uses superclass interfaces and polymorphism to keep application code flexible across multiple runtime subclasses.
- How deep it goes
- Defines the principle and demonstrates refactoring with shapes and books, but stops short of a general implementation checklist.
- Examples
- Demonstrates Shape with Rectangle and Circle, then Book with Fiction, Cookbook, and their attribute subclasses.
- What you can do after
- Evaluate designs for concrete-subclass coupling and apply polymorphic superclass interfaces to support multiple subclasses.
Read how Object-Oriented Software Design in C++ explains code to the interface principle →
Related concepts
- polymorphismuses · Polymorphism is a programming-language capability that lets a common interface or operation work with values of different types while allowing behavior to vary by type or implementation.
- superclassuses · A superclass is a class from which another class inherits members, structure, state, or behavior.
- overrideused by · Overriding is defining a more specific implementation that replaces inherited behavior for a type or object while preserving the operation’s interface.
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