Download - Simplicity. Grigas
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simplicity 0.3
Osvaldas [email protected]
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complexity 0.3
Osvaldas [email protected]
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inspired by
DanNorth
RichHickey
J.B. Rainsberger
Michael Feathers
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Edsger Dijkstra (1980)
Computing's central challenge,"How not to make a mess of it",
has not been met.
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agile
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agile
continuous improvementbased on frequent feedback
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iterative development
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incremental development
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DONE
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embrace the transient natureof your code
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Russ Miles
Complexity is the silent killer of delivering change at the right time.
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simplicity is prerequisite for agility
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what is simplicity ?
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Nothing is more simplethan a single giant button
MacBook Wheel
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what "simple" isnt ...
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what "simple" isnt ...
familiar / convenient
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what "simple" isnt ...
familiar / convenient
small / concise
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what "simple" isnt ...
familiar / convenient
small / concise
beautiful / elegant
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Simplicity -- the art of maximizing the amount of work not done -- is essential.
from the agile principles
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YAGNI
from the agile principles
Simplicity -- the art of maximizing the amount of work not done -- is essential.
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Technical excellence andgood design enhances agility.
from the agile principles
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Martin Fowler
Design is there to enable you tokeep changing the software easily.
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when it comes to design ...
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COMPLEXITY SUCKS
SIMPLICITY RULES
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COMPLEXITY SUCKS ...
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COMPLEXITY SUCKS ... your brain power
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COMPLEXITY SUCKS ... your brain power
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Rich Hickey
Once your software is of a certain size, complexity is gonna
dominate what you can do.
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essentialcomplexity
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essentialcomplexity
your code
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essentialcomplexity
your code
libra
ries
frameworks
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essentialcomplexity
langua
geruntime
your code
libra
ries
frameworks
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accidental
complexity
essentialcomplexity
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SIMPLICITY RULES ...
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SIMPLICITY RULES ... are
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SIMPLICITY RULES ... are
The 4 Rules of Simple Design
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SIMPLICITY RULES ... are
The 4 Rules of Simple Design1) passes all tests
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SIMPLICITY RULES ... are
The 4 Rules of Simple Design1) passes all tests
2) clear, expressive names
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SIMPLICITY RULES ... are
The 4 Rules of Simple Design1) passes all tests
2) clear, expressive names3) no duplication
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SIMPLICITY RULES ... are
The 4 Rules of Simple Design1) passes all tests
2) clear, expressive names3) no duplication4) minimal
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rule #4: minimal
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the less code,the better
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code folding
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codegenerators
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dependencymanagers
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stop typing.
think!
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test-first(TDD / BDD)
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rule #3: no duplication
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primitive obsession
duplication in behavior
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data clump
duplication in structure
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refactoring
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rule #2: clear, expressive names
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small, focused methods
reduce cyclomatic complexity
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small, focused classes
single responsibility
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AccountService
AccountManager
AccountHandler
AccountUtils
AccountHelper
AccountImpl
AccountData
AccountDTO
AccountInfo
AccountDetails
AccountObject
AbstractAccount
BaseAccount
CustomAccount
SimpleAccount
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refactoring
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rule #1: passes all tests
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unit testing
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testability & good design
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testability & good design
(but not integration tests)
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inheritance-based design
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wget -qO- http://c2.com/ | tr -cs '[:alpha:]' '\n' | sort | uniq
composition
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dependencies
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auto-import
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refactoringtools
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AG
F
DC
introduce indirection
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AB
E G
F
DC
introduce indirection
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AB
E G
F
DC
followthe law of Demeter
introduce indirection
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modularity
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coupling
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add an interface?
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layered architectures
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add remoting?
SOAP
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enterprise grade decoupling?
ESB
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enterprise grade decoupling?
ESB
assumptions
assumptions
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interface segregation
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tell, dont ask
high cohesion
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dependency inversion
role
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anti-corruption layer
adapter
role
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notify
Payment Order Auditor
FinancialEvent
Listener
Mongo Audit Trail
log
AuditTrail
MongoAudit
Recordsinsert
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Payment Order
AuditDAO
AuditDAOImpl
insert
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further decoupling
queue
publish subscribe
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use cases& business rules
framew
ork
persist
ence
fram
ewor
k
web
DB
infrastructure
messagingQUEUE
task
scheduler
WS
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DomainLogic
FrameworkFramework
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DomainLogicDomainLogic
FrameworkFramework
accidentalcomplexity
complexityleak
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@Entity@Table(name = "orders", schema = "com"})public class Order implements Serializable {
@Id @GeneratedValue(strategy = SEQUENCE, generator = "order_seq") @Column(name = "ID", unique = true, nullable = false) private Integer id;
@Column(name = "NUMBER", nullable = false, length = 8) private String number;
@ManyToMany(fetch = FetchType.LAZY, cascade = CascadeType.ALL) @JoinTable(name = "order_items", catalog = "com", joinColumns = {@JoinColumn(name = "ORDER_ID", updatable = false, nullable = false)}, inverseJoinColumns = {@JoinColumn(name = "ITEM_ID", updatable = false, nullable = false)}) private Set items = new HashSet();
}
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the law of leaky abstractions
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home-grownframeworks
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libraries
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state& side effects
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values& pure functions
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functional style imperative style
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functional style
expressions
imperative style
statements
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functional style
expressions
immutable values
imperative style
statements
mutable state
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functional style
expressions
immutable values
data transformations
imperative style
statements
mutable state
side effects
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functional style
expressions
immutable values
data transformations
recursion &polymorphism
imperative style
statements
mutable state
side effects
looping &branching
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stepping out ofcomfort zone
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Edsger Dijkstra (1980)
Computing's central challenge,"How not to make a mess of it",
has not been met.
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Imdone
