Pure virtual member function
A pure virtual member function is a virtual function declared as requiring derived classes to provide an override, typically making its declaring class abstract.
100 C++ Mistakes and How to Avoid Them
A pure virtual function is a C++ virtual member function declared without a required implementation in the declaring class and intended to be overridden by derived classes.
- How it is used
- Uses pure virtual functions to express shared behavior without forcing unrelated classes into an implementation hierarchy.
- How deep it goes
- Defines the interface pattern and shows implementations, but stops short of detailed object-model or language-runtime internals.
- Examples
- Uses Square, Horse, Moveable, dynamic_cast, and a collection of Moveable pointers to contrast misleading and meaningful relationships.
- What you can do after
- Apply it via an interface-like base when classes share meaningful behavior, while avoiding inheritance based only on matching method names.
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Learn C++ by Example
A pure virtual function is a virtual member function declared without an implementation requirement in its declaring class, making that class abstract unless overridden.
- How it is used
- Defines a polymorphic interface for blob types that must provide stepping and step-count behavior.
- How deep it goes
- Explains declaration, abstractness, overriding, and v-table dispatch, while deferring broader special-member-function details.
- Examples
- Uses a Blob race, a StepperBlob implementation, pointer-based dispatch, and an assertion checking two-step movement.
- What you can do after
- Build it from scratch as an abstract C++ interface and implement checked concrete subclasses.
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Related concepts
- contractpart of · An API contract is a specification of the operations, data, and behavioral expectations that govern interactions between software components.
- abstract classpart of · An abstract class is a class intended as a base for subclasses, often not directly instantiable, that can provide shared implementation and declare operations subclasses must implement.
- natural language interfacepart of · A natural language interface enables interaction with a system through human-language text or speech.
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