Code - Fu: Defensive Programming
- 1. Code- Fu: Defensive Programming With great power comes great responsibility ~ Peter Paker’s Dad’s Brother Ben
- 2. 1980 A radiation therapy machine was directly responsible for at least 5 patient deaths 1996 A US$1 billion exploded 40 seconds after takeoff 2012 Apple Maps gives us directions to nowhere 2016 ABSA bank double charges clients Why learn another design pattern? Because: BUGS!
- 3. Intro to Code-Fu Defensive programming, simply put, is programming with the intent to anticipate likely failure points. Defensive programming practices are often used where high reliability, safety or security is needed.
- 4. Intro to Code-Fu cont... Defensive programming aims to improve software and source code, in terms of: 1. General quality (reduce bugs) 2. Comprehensive code a. Clean b. Readable c. Understandable d. Reliable e. Maintainable f. Testable g. Robustness 3. Predictable behaviour
- 5. Mastering the ways of Code-Fu Defensive programming is really programming for the real world where if anything can go wrong it will.
- 6. Real world programs 1. Are not in isolation, you can expect user input or external input 1. Are built & maintained by teams and the individuals making the team can change over time (imagine open source projects) 1. Need to work
- 7. External/User input ● Never trust external/user input ● Remember there are also users with malicious intent What helps ● Protect your code from invalid data (data validation) ● User whitelists not blacklists ● Use database abstraction (e.g. PDO for PHP)
- 8. We work in Teams ● Trust your fellow developers but DON’T trust their code ● Defensive Programming is much like Defensive Driving assume that everyone around us can potentially and possibly make mistakes. ● Teams can consists of individuals working from different planets What helps ● Enforcing coding standards (naming conversions included) ● Write SOLID code (Encapsulation) ● Write code for the maintainer (The maintainer can be future you) ● Parameter checks at the beginning of a function/method ● Unit tests, Regression testing, Integration tests
- 10. Check params + Encapsulation // ES5
- 11. Programs need to work ● Imagine paying R200 per month for Software that works 30% of the time What helps ● Add diagnostic code, logging and tracing (Bugsnag/Sentry) ● Security tests
- 12. As a Defensive programmer you need to have a healthy dosage of paranoia
- 14. Good/Bad?
- 15. QUESTIONS?