Back-2-Basics: Code Contracts
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This document summarizes a presentation on code contracts, which are preconditions, postconditions, and class invariants that define the expectations and promises of software elements. The presentation discusses the background of design by contract and how contracts can be used throughout the software lifecycle to write better code, analyze designs, implement and reuse components properly, avoid bugs, automatically document software, help with testing and debugging, and assist project managers. It also advertises a DVD and conference photos for sale, and lists local user groups in San Diego.
Back-2-Basics: Code Contracts
- 3. dotNetDave Conference DVD!Packed full of:Videos of all sessions from 2010 & 2011(1)!Slide decks from 2011 & 2010!Demo projects from 2011 & 2010!David McCarter’s .NET interview Questions!ExtrasConference Photos from 2010!Surprise videos!Book + DVD $25!Only $15!
- 4. Check Out Your Local User Groups!San Diego Cloud Computing User Groupwww.azureusergroup.com/group/sandiegoazureusergroupSan Diego .NET Developers Groupwww.sddotnetdg.orgSan Diego .NET User Groupwww.sandiegodotnet.comSan Diego SQL Server User Groupwww.sdsqlug.org
- 5. Agenda5
- 6. Overview
- 7. Introduction to Code ContractsNew API + tools from MicrosoftSystem.Diagnostics.ContractsMSIL rewritingInspired by Spec#Included in .NET 4.0 but…Download available now for .NET 3.5 and VS2008http://research.microsoft.com/en-us/projects/contracts/
- 8. Design by ContractA discipline of analysis, design, implementation, managementApplications throughout the software lifecycle:Getting the software right: analysis, design , implementationDebugging & testingAutomatic documentationGetting inheritance rightGetting exception handling rightMaintenanceManagement
- 9. BackgroundWork on “axiomatic semantics”:R.W. Floyd (1967)C.A.R. Hoare (1969, 1972)E.W. Dijkstra (1978)1970’s languages: CLU, AlphardEiffel (from 1985): connection with object technology90s and onward: contract additions to numerous languages: C++, Java, C#, UML
- 10. Design by ContractEvery software element is intended to satisfy a certain goal, or contractFor the benefit of other software elements (and ultimately of human users)The contract of any software element should beExplicitPart of the software element itself
- 11. The three questionsPreconditionWhat does it expect?What does it promise?What does it maintain?PostconditionClassinvariant
- 12. 12Contracting componentsDefinition of what each element of the functionality:Expects (precondition)Promises (postcondition)Maintains (invariant)Does not have to be complete (but wait)
- 13. What we do with contractsWrite better softwareAnalyzeDesignReuseImplementUse inheritance properlyAvoid bugsDocument software automaticallyHelp project managers do their job(with run-time monitoring)Perform systematic testingGuide the debugging process13
- 15. Summary