FIT3077 Lecture 6: Principles of OO Design 3+4
22 Jun 2018
School
Department
Course
Professor
Principles of OO Design 3
Software Reuse
●Oen stated goals
●Not code copying
○Copy pasng from one program to another
○Maintenance must be done by us
●Don’t maintain it
●Don’t distribute it
●Only need to link it
●Depend only on the interface of the reused product
Principles of Package Architecture
●Packages allow to group classes together into single, higher level, module
●How to decide which classes belong together?
○The Package Cohesion Principle
■The Release Reuse Equivalency Principle
●A reusable modules cannot be reused unless there is a release
system to manage new versions
●Clients need to be able to choose which version of the module they
want to use
●Clients will refuse to reuse modules that do not have the release
management as described above
●Packages are a good candidate for releasable enty
■The Common Closure Principle
●Soware maintenance is even more important than soware reuse
●Whenever a change must be made, all the affected modules affected
must be:
○Rebuilt, Retested, Released
●Ideally, all changes to be limited to a single package
●Should group together classes that are likely to change together for
the same reasons
●Should group together classes that cannot be completely closed with
respect to each other
●Closely related to the open-closed principle
■The Common Reuse Principle
●Classes that aren’t reused together should not be grouped together
●Rare for classes to be reused in isolaon as they typically collaborate
with other classes that go together to form a reusable abstracon
Document Summary
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