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Elegant Objects and Cactoos
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Filipe Freire
December 21, 2017
Programming
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250
Elegant Objects and Cactoos
Overview of the EO paradigm and small overview of the Cactoos library for Porto Codes Meetup
Filipe Freire
December 21, 2017
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Transcript
Elegant objects & Cactoos Filipe Freire 21 December 2017
Quick intro Learner, tester, developer, husband OSS contributor 2y work
as a “coding” tester 1y work as a developer Currently @ filfreire.com 2
Elegant Objects 3
It’s an OOP paradigm 4
Book Yegor Bugayenko @yegor256 www.yegor256.com 5
Book Yegor Bugayenko @yegor256 www.yegor256.com Set of recommendations: - Cleaner
code - Better classes - Visible architecture 6
Disclaimer: You can find out more at yegor256.com Youtube @yegor256
and on the EO books. 7
So, what are the recommendations? 8
Getters Setters Mutable objects Static methods Annotations Data Objects Type
Casting Etc. 9
Getters Setters Mutable objects Static methods Annotations Data Objects Type
Casting Etc. 10
Don’t treat objects as data structures bags of data.
Ever. 11
Maintainability > everything else 12
“Objects as living beings” Birth Working life Retirement 13
Some examples… 14
Birth 15
Code Free Constructors 16
17
“Object’s name != job title” 18
Object’s name != job title Meaning: Avoid the use of
“-ER” 19
Helper, Handler, Writer, Reader, Converter, Observer, Listener, Sorter, Encoder, Decoder,
… 20
Helper, Handler, Writer, Reader, Converter, Observer, Listener, Sorter, Encoder, Decoder,
… 21
An object isn’t: 1) A link between worlds 2) A
collection of procedures plus data 22
An object is: 1) Self-sufficient 2) Representative of encapsulated
data 23
A Finder of Prime Numbers vs A List of numbers
that returns only primes 24
Education & Work life 25
No Getters and Setters. Not even once. 26
No Getters and Setters ?! ?! 27
Again, don’t treat objects as bags of data. Ever.
28
Computer-style: 29
Human-style: 30
“An object works by contracts” 31
“An object works by contracts” Always use interfaces 32
Example “I want results for a Tennis match” Tennis_31Feb.xlsx TENNIS.txt
tennis_res.json Sources: … 33
Example “I want results for a Tennis match” Tennis_31Feb.xlsx TENNIS.txt
tennis_res.json Sources: … ExcelTennisMatch TextTennisMatch JsonTennisMatch 34
Example “I want results for a Tennis match” ExcelTennisMatch TextTennisMatch
JsonTennisMatch TennisMatch GameMatch implement extends 35
Excel, Text, Json, etc. Contract stays the same More Decoupling
and more Maintainability 36
“A good object should never change his encapsulated state.” 37
“A good object should never change his encapsulated state.” 38
Be immutable
This can change State is the same 39
Some benefits Thread Safety Avoiding Temporal Coupling Avoiding side effects
Avoiding identity mutability (more at http://yegor256.com/2014/06/09/objects-should-be-immutable.html) 40
Retirement 41
Don’t accept null arguments Don’t return null 42
- Hello, is it a software department? - Yes. -
Let me talk to your employee "Jeffrey" please. - Hold the line please... - Hello. - … 43
- Hello, is it a software department? - Yes. -
Let me talk to your employee "Jeffrey" please. - Hold the line please... - Hello. - Are you NULL? (more at http://www.yegor256.com/2014/05/13/why-null-is-bad.html) 44
There’s more to it, Let’s save it for another talk
45
https://github.com/yegor256/cactoos 46
Useful building blocks from Guava, Apache Commons, JDK + EO
paradigm 47
Meaning… No null No code in constructors No getters and
setters No mutable objects No static methods, not even private ones (among other stuff) 48
Example 1 49
Example 2 50
Example 3 51
Summing up 52
Maintainability 53
–W. Edwards Deming "Build quality into the product rather than
trying to test it in later." 54
Quality from the start Force strict control of code quality.
Ex: Static Analysis -> mandatory 55
Thank you. Questions? filfreire filrfreire filfreire.com 56