Libraries versus Frameworks
Damien Cassou, Stéphane Ducasse and Luc Fabresse
http://stephane.ducasse.free.fr
Outline
- What are libraries?
- What are frameworks?
- Some guidelines to create a new framework
What are Libraries?
- a library is a set of code entities (classes and methods)
- the client of a library sends requests to the library
- the library returns responses
- the main code (dark blue) is in the client
.
What are Frameworks?
- a framework is a set of code entities (classes and methods), just like in libraries
- the framework has abstractions (i.e., holes) to be implemented
- the client implements the abstractions to parameterize the framework
- the main code (dark blue) is in the framework
.
Libraries versus Frameworks
- Library
- You call it
- You use callbacks to extend it
- Framework
- Hollywood principle: Don't call me, I will call you
Libraries versus Frameworks
| Library |
Framework |
|---|
| The client instantiates the classes |
The framework instantiates the classes |
| The client invokes library functions |
The framework invokes code in the client |
| The client is responsible for the flow |
The framework is responsible for the flow |
Inheritance as Parameterization
- a client parameterizes a framework by overriding operations
- the template method design pattern is often used
.
MyGUI new newWindow --> creates a window of width 25
Framework Design
- Needs at least 3 clients
- "A Pattern Language for Developing Object-Oriented Frameworks", by Don Roberts and Ralph Johnson
- Framework design often relies on whitebox abstractions
- framework are extended by inheritance
- blackbox abstraction is also possible: usage of composition
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