?e??d?????e? ?????a

1
?e??d?????e? ?????aµµat?sµ?? ??
S?ed?ast??? ???t?pa (1)
?a?a???t?? Sf?ts??, PhD http//aetos.it.teithe.gr/
sfetsos/ sfetsos_at_it.teithe.gr
2
St????

• Ge???? ??a ta ???t?pa
• S?ed?ast??? ???t?pa
• ?atas?e?ast??? (Creational)
• ??µ??? (Structural)
• S?µpe??f????? (Behavioral)

3
S?ed?ast??? ???t?pa
?p? t?? ????te?t?????
Christopher Alexander ????t??t??a?,
1979 ??a?????s? ?????? ?a?a?t???st???? se s??d?a
?a??? p???t?ta? ? a?????... ?????? ??se?? se
????? ???ß??µata ??a pa?a???? s?ed??? ?a???
p???t?ta?
4
S?ed?ast??? ???t?pa
St? ????sµ???
????? '90. ?p?????? p??ß??µata st? ????sµ???
ta ?p??a epa?a?aµß????ta? ?p???e? ? d??at?t?ta
s?ed?as?? ????sµ???? µe p??t?pa ?? Gamma, Helm,
Johnson ?a? Vlissides (Gang of Four -
GoF) ap??t?sa? ???.
5
S?ed?ast??? ???t?pa
???sµ??

• ??a p??t?p? pe?????fe? ??a epa?a?aµßa??µe??
  p??ß??µa, se
• ??a s???e???µ??? pe??ß?????, ?a? µ?a ?a??
  te?µ????µ??? ??s?
• t??.
• S???pe?e?
• ?pa?a???s?µ?p???s? s?ed???
• ?pa?a???s?µ?p???s? ??d??a
• ??a?e???s? a??a???
• ?? GoF ?at??t?sa? ??a? ?at????? µe 23 p??t?pa
  s?ed?as??.

6
?e????af? t?? ???t?p??
? ?at?????? t?? ?a?a?t???st???? t?? p??t?p?? GoF
7
S?ed?ast??? ???t?pa
?a???e? S?ed?as?? µe ta ???t?pa

• S?ed?????µe µe d?as??d?se?? (d?epaf?? ?
  af???µ??e? ???se??)
• ???t?µ??µe t?? s???es? (composition) ap? t??
• ???????µ???t?ta (inheritance)
• ???s???µe t? a????e? ?a? t? e????a?????µe
  (encapsulate)

8
S?ed?ast??? ???t?pa
St???e?a t?? p??t?p??
?at?????e? ?atas?e?ast??? (Creational)
?s??????ta? µe t?? d?e??as?e? d?µ??????a? t??
a?t??e?µ???? ??µ??? (Structural) ?s??????ta? µe
t?? d?e??as?e? s???es?? t?? ???se??/a?t??e?µ????
S?µpe??f????? (Behavioral) ?s??????ta? µe t???
t??p??? µe t??? ?p????? ?? ???se?? a????ep?d????
?a? ?ata??µ??? t?? a?µ?d??t?te?
9
Strategy (St?at?????) 1/6
?at?????a Behavioral S??p?? ?? p??t?p? a?t?
????e? ?a? e?s?µat??e? µ?a ???????e?a a??????µ??
(sa? a?t??e?µe?a) ep?t??p??ta? ta?t?????a ?a?
t?? e?a??a?t??? e?t??es? t??. ?p?t??pe? t?
µetaß??? t?? a??????µ??, a?e???t?ta ap? t???
pe??te? p?? t??? ???s?µ?p?????. S?????µa -
10
Strategy (St?at?????) 2/6

• ???s?µ?p??e?ta? st?? pe??pt?se?? ???p???s??
  e??? ??????
• ?e????? a??????µ?? (p.?. ta????µ?s?) a???
  ?a? p?????
• d?af???p???se?? t?? (p.?. f?sa??da?,
  e?sa????? ?.t.?.).
• ??t??e? s?µpe??f???? e??a? s????? st??
  a?t??e?µe??st?ef?
• p????aµµat?sµ? ?a? pa?ap?µp??? s?????? st??
  ?????-
• ??µ???t?ta. ?? p??t?p? St?at?????
  a?t?µet?p??e? t?t??a
• p??ß??µata st?????µe?? ??? µ??? st??
  ???????µ???t?ta,
• a??? ?a? st? s???es? a?t??e?µ????.
• ?fa?µ??e? t?? a??? t?? ??t?st??f?? t??
  ??a?t?se??
• a?a??????ta? t?? ?e???? a??????µ? ?a? t??
  ?ept?µe?e??
• ???p???se?? ?a e?a?t??ta? ap? afa???se??.

11
Strategy (St?at?????) 3/6

• ???s?
• ?ta? ????µe s?s?et???µe?e? ???se?? p??
  d?af????? µ??? ??
• p??? t?? s?µpe??f???.
• ?a???e? se µ?a ???s? t? d??at?t?ta ?a e?te?e?
  µ?a ap? p?????
• s?µpe??f????.
• ?ta? ?p?????? p????? pa?a??a??? t?? ?d???
  a??????µ??. ???e
• pa?a??a?? e?s?µat??eta? se ??p??a
  St?at?????.
• ??a ???s? ????e? p????? s?µpe??f???? p??
  ep??????ta? ap?
• p???ap??? e?t???? s??????? t?? ?p??e?
  µp????µe ?a
• e?a??st?p???s??µe µe e?s?µ?t?s? t??? se
  st?at??????.

12
Strategy (St?at?????) 4/6
??af??et???? a??????µ?? ???p?????ta? sa?
s???e???µ??e? ?p????se?? t?? d?as??des?? Strategy
(d?epaf?? ? af???µ???? ???s??).
13
Strategy (St?at?????) 5/6
interface FortuneCookies public void
print() class Six implements FortuneCookies
public void print()
System.out.println("6-Exi") class Five
implements FortuneCookies public void print()
System.out.println("5-Pente") class
Four implements FortuneCookies public void
print() System.out.println("4-Tessera")
class Three implements FortuneCookies
public void print() System.out.println(
"3-Tria") class Two implements FortuneCookies
public void print()
System.out.println("2-Dyo") class One
implements FortuneCookies public void print()
System.out.println("1-Ena") class
Null implements FortuneCookies public void
print() System.out.println("Tipote")
? d?epaf? ?? ???se?? t?? a??????µ??


14
Strategy (St?at?????) 6/6
class Dice public int throwIt() return
(int)(Math.random()6)1 class strategyTest
static void goodFortune() int luckyNum
new Dice().throwIt() FortuneCookies fc.
switch (luckyNum) case 6 fc new
Six()break //d?µ??????a a?t??. case 5
fc new Five()break case 4 fc new
Four()break case 3 fc new
Three()break case 2 fc new
Two()break case 1 fc new
One()break default fc new
Null() fc.print() // e?t??es?
public static void main(String
args) goodFortune()
15
Singleton (???ad?a??) 1/3

• ?at?????a Creational
• S??p??
• ???a? t? p??t?p? p?? ???s?µ?p??e?ta? ?ta? ?????µe
  ?a
• e?asfa??s??µe ?t? µ?a ???s? ?a ??e? µ??? ??a
  st??µ??t?p?
• ?a? ?t? ?a pa???e? ??a ?a?????? s?µe?? p??sßas??
  se a?t?.
• S?????µa -

16
Singleton (???ad?a??) 2/3

• ???a? ??a p??t?p? p?? ???s?µ?p????µe ?ta?
  ?????µe ?a d?µ??????s??µe
• µ??? ??a a?t??e?µe?? se µ?a ???s?.
• ? ????? t?? µ??ad?a??? a?t??e?µ???? e??a?
  s?????? ? d?a?e???s? t??
• ?p????p?? a?t??e?µ???? t?? efa?µ????.
• ?a µ??ad?a?a a?t??e?µe?a d?µ????????ta? ap? µ?a
  e?d??? µ???d? p??
• - e????e? a? ??p??? a?t??e?µe?? ??e? ?d?
  d?µ???????e?. ?? ?a?, ?
• µ???d?? ep?st??fe? ap??? ??a? de??t? p???
  t? ?p????? a?t??e?µe??.
• ?? ???, ? µ???d?? d?µ?????e? ??a ???
  a?t??e?µe?? ?a? ep?st??fe?
• de??t? p??? a?t?.
• O ?atas?e?ast?? t?? ???s?? d????eta? ??
  p??state?µ???? (protected) ?
• ?d??t???? (private) ??a ?a e?asfa??ste? ?t?
  ?a d?µ???????e? t? a?t??e?µe??
• µ??? µ?s? a?t?? t?? µe??d??.

17
Singleton (???ad?a??) 3/3

• St?? Java
• public class Singleton
• private static Singleton instance // ?
  instance null
• / ????s? p??sßas?? st?? ?atas?e?ast? /
• private Singleton() //d?µ?t?? µ??? ?
  Singleton µp??e? ?a t?? ???s?µ?p???se?
• public static Singleton getInstance()
• if (instance null)
• instance new Singleton()
• return instance

18
Adapter (???sa?µ???a?) 1/9

• ?at?????a Structural
• S??p??
• ? µetat??p? t?? d?as??des?? µ?a? ???s?? se µ?a
  ???? (p??
• a?aµ????? ta p?????µµata pe??te?). ?p?t??pe? se
  µ?
• s?et???µe?e? ???se?? (as?µßate? d?as??d?se??) ?a
• s???e?t?????s??? se ??a ????? p????aµµa.
• S?????µa Wrapper (ed?pe??t????µa a?t??e?µ????)
• ??? ?at?????e? p??sa?µ??e?? a?t??e?µ????
  (object adapters)
• ?a? p??sa?µ??e?? ???se?? (class adapters).

19
Adapter (???sa?µ???a?) 2/9

• ??µ?
• ? p??sa?µ???a? ???s?? ???s?µ?p??e? t?? p???ap??
• ???????µ???t?ta ??a ?a p??sa?µ?se? µ?a
  d?as??des?
• se µ?a ????
• ? p??sa?µ???a? a?t??e?µ???? ßas??eta? st??
  s???es?
• a?t??e?µ???? (composition) ?a? d?aß?ßas?
  µ???µ?t??
• (delegation)

20
Adapter (???sa?µ???a?) 3/9
?? s?µµet????te?...
Target ??as??des? p?? ???s?µ?p??e? ?
Client. Client ???s?µ?p??e? a?t??e?µe?a s?µf??a
µe t?? d?as??des? Target. Adaptee ? d?as??des?
p?? ??e???eta? p??sa?µ???. Adapter ???sa?µ??e?
t?? d?as??des? t?? Adaptee st? d?as??des? t??
Target.
21
Adapter (???sa?µ???a?) 4/9
???sa?µ??e?? ??t??e?µ???? (Object Adapters)

• ? p??sa?µ???a? a?t??e?µ???? ßas??eta? st??
  s???es? a?t??e?µ????
• composition) ?a? d?aß?ßas? µ???µ?t??
  (delegation).
• ???????µe? t?? d?epaf? t?? Target p??
  ???s?µ?p??e? ? Client ?a? ?at??e?
• ??a a?t??e?µe?? t?? Adaptee.
• ?ta? ? Client ?a?e? t?? µ???d? request() µe t?
  a?t??e?µe??-Target, ? p??sa?µ???a?
• t? µetaf???e? - p??sa?µ??e? st?
  specificRequest() t?? Adaptee (a?af???).
• ? p??sa?µ???a? a?t??e?µ???? ep?t??pe? t??
  ???se?? Client ?a? Adaptee ?a e??a?
• te?e??? as??dete?. ???? a?t?? ??????e? ?a?
  ??a t?? d??.

22
Adapter (???sa?µ???a?) 5/9
???sa?µ??e?? ??t??e?µ???? (Object Adapters)
class Target public void request() class
Adaptee public void specificRequest()
System.out.println("Adaptee SpecificRequest")
class Adapter extends Target private Adaptee
adaptee public Adapter(Adaptee a)
adaptee a public void request()
adaptee.specificRequest() class TestAdapter
public static void main(String args)
Adaptee a new Adaptee() Target t new
Adapter(a) t.request()
23
Adapter (???sa?µ???a?) 6/9
???sa?µ??e?? ???se?? (Class Adapters)

• ? p??sa?µ???a? ???s?? ???s?µ?p??e? t?? p???ap??
  ???????µ???t?ta ??a ?a
• p??sa?µ?se? µ?a d?as??des? se µ?a ????
• ???????µe? t?? d?as??d?se?? t?? Target p??
  ???s?µ?p??e? ? Client ?a? t??
• Adaptee.
• St?? Java epe?d? de? ?p?st????eta? ? p???ap??
  ???????µ???t?ta ?a p??pe? µ?a
• ap? t?? d?as??d?se?? ?a ???????µe?ta? ap?
  d?epaf? t?? Java. H target ?a?
• ? Adaptee ?a µp????sa? ?a e??a? d?epaf??
  Java.
• H request() st?? Target µetaf???eta?-p??sa?µ?
  ?eta? st?? specificRequest() p??
• ???????µe?ta? ap? t?? ???s? Adaptee.

24
Adapter (???sa?µ???a?) 7/9

• ?a??de??µa
• Ta ???p???s??µe t??? p??sa?µ??e?? ???s?? ?a?
  a?t??e?µ???? p?? p??sa?µ????? t?? ???s? TextView
  ?ste ?a ta?????e? µe t?? d?as??des? t?? ???s??
  Shape.
• ?? d?af???? st?? d?? a?t?? ???se?? e??a?
• ?? ???t? p?a?s??? (? shape t? ????e? µe t??
  ap??a?t? ????e?, e?? ? TextView
• µe t? ???? ?a? µ????).
• ? Shape ????e? t?? µ???d? CreateManipulator()
  ??a ?a ?e????eta? t?? ????s?
• (animation), e?? ? TextView de? ??e? a?t?st????
  µ???d?.
• ? ???s? TextShape ?a e??a? ? p??sa?µ???a? µeta??
  a?t?? t?? d?af??et????
• d?as??d?se??.

25
Adapter (???sa?µ???a?) 8/9
???p???s? µe ???sa?µ???a ???s??

• ??????µe t?? TextShape ?a ???????µe? t??
  d?as??des? Shape ?a? t?? ???p???s?
• (implementation) t?? TextView.
• ???a??-?pe??????? (override) t?? µe??d??
  BoundingBox() µetat??p??ta? t??
• d?as??des? t?? TextView ?ste ?a p??sa?µ?ste?
  st?? d?as??des? Shape.

• ???a??-?pe???????
• (override) t?? µe??d??
• IsEmpty() ??a ?a
• ste????µe t? µ???µa
• ?ate??e?a? st??
• IsEmpty() t?? TextView.
• ???sµ?? t?? µe??d??
• CreateManipulator() ap?
• t?? a???.

26
Adapter (???sa?µ???a?) 9/9
???p???s? µe ???sa?µ???a ??t??e?µ????

• ? ???sµ?? t?? TextShape ???p??e? ??a de??t? ??a
  t?? d?as??des? TextView.
• ??????p??e? t?? de??t? st?? d?µ?t?.
• ?a?e? µe??d??? µe t? a?t??e?µe?? t?? TextView
  p?? ?at??e?
• ????e? t?? µ???d? CreateManipulator() ap? t??
  a??? (?p?? p???).

27
Bridge (G?f??a) 1/5

• ?at?????a Structural
• S??p??
• ? ap?s??des? µ?a? afa??es?? ap? t?? ???p???s?
  t??, ?ste ?a? ta d?? ?a µp????? ?a µetaß?????ta?
  a?e???t?ta.
• S?????µa Handle/Body

28
Bridge (G?f??a) 2/5

• ?fa??es? ?a? ???p???s? s??d???ta? µ???µa,
  ?????ta?
• d?s???? t?? ep??tas?, t??p?p???s? ?a?
  epa?a???s?µ?p???s?
• t?? ??d??a.
• ?µ?? µ?a afa??es? µp??e? ?a ??e? p?????
  ???p???se??
• (?p????se?? p?? ???p????? t?? µe??d??? t??
  af???µ????
• ???s??)
• ?ta? µ?a afa??es? ??e? pe??ss?te?e? ap? µ?a
  ???p???se??, t?te
• ???s?µ?p????µe ???????µ???t?ta.
• ? G?f??a ???s?µ?p??e?ta? e?e? p?? s?µßa?????
  µetaß????
• st?? afa??es? a??? ?a? st?? ???p???s? t??
  afa??es??.

29
Bridge (G?f??a) 3/5

• ? afa??es? (Abstraction) s?ss?µat??e? µ?a
  ???p???s? (Implementor).
• H ???s? RefinedAbstraction e??a? µ?a ep??tas?
  t?? afa??es??
• ???s?µ?p????ta? ep?p???? µe??d??? ??a
  pe??ss?te?? ?e?t???????t?ta.
• ? d?epaf? (Implementor) pa???e? µ?a d?epaf? ??a
  t?? ???se?? ???p???s??
• (t?? ???se?? ConcreateImplementor)
• H ???s? RefinedAbstraction af??? t?? afa??es?
  ?a? ??? t?? ???p???s?.
• ??t? s?µa??e? ?t? ?ept?µ???e? t?? ???p???s??
  ???ß??ta? ap? t?? Client.

30
Bridge (G?f??a) 4/5

?a??de??µa To t??e???t??? t?? t??e??as?? (ap?
t? ß?ß??? Head First Design Patterns)
?e a?t? t?? ??s? ?p?st??????µe µetaß???? st??
???p???s? a??? ??? st?? afa??es?. ?? d????µa ??
?a ???e? ?ta? t? t??e???t??? a????e? ??s? Ta
s?ed??s??µe ?ts? ?ste ?a ?p?st???- ???µe
µetaß???? t?s? st?? ???p???s? ?s? ?a? st??
afa??es?.
31
Bridge (G?f??a) 5/5

???s?µ?p????µe to p??t?p? G?f??a p?? ep?t??pe?
µetaß???? st?? ???p???s? ?a? st?? afa??es?
t?p??et??ta? ?a? ta d?? µ??? se d?af??et????
?e?a???e? ???se??.
32
Composite (S???et?) 1/5

• ?at?????a Structural
• S??p??
• S????te? a?t??e?µe?a se de?d??e?de?? (s???ete?)
  d?µ?? ??a t?? a?apa??stas? ?e?a?????
  tµ?µat??-????. ?? p??t?p? s?ed?as?? "S???et?"
  ep?t??pe? sta p?????µµata pe??te? ?a
  d?a?e??????ta? µe e??a?? t??p? t?s? ta a?e???t?ta
  a?t??e?µe?a ?s? ?a? s????se?? a?t??e?µ????.
• S?????µa -

33
Composite (S???et?) 2/5

• ??a efa?µ??? µp??e? ?a pe????e? ? ?a
  pe???aµß??e? s???eta
• a?t??e?µe?a (p.?. G?af???) ? µeµ???µ??a
  a?t??e?µe?a
• (p.?. G?aµµ?).
• ?? ???aµe ?a p??s??s??µe st? s?st?µa µ?a ??a
  s???et? ???s?
• (p.?. ?????a), t?te ? ??d??a? t??
  p?????µµat?? pe??t?,
• ?a p??pe? ?a t??p?p????e? ??a ?a e??a?
  d??at?? ? ?e???sµ?? t??
• ???? a?t??e?µ???? t?p?? ?????a?.
• ?? p??t?p? S???et? d??e? t? ??s?. ??µ???????µe
  µ?a ???s? p??
• epe?te??e? t?? ßas??? ???s? a?t??e?µ????
  ?a? ?e????eta? µe t??
• ?d?? t??p? t?s? ta µeµ???µ??a a?t??e?µe?a,
  ?s? ?a? ta s???eta.

34
Composite (S???et?) 3/5

????t??

• ??? ??????ta? ?? µ???d?? Add(), Remove(),
  getChild()
• St?? Component ??a d?af??e?a
• (?d?a ?e?t?????a ??a ??a ta
• a?t??e?µe?a)
• St?? Composite ??a asf??e?a (???e
• ???s? ap? ep?µ????? a?t??. ?a
• p???a??se? ????? ?at? t?? µeta???tt?s?.

35
Composite (S???et?) 4/5
Component ??a ßas??? ???s? a?t??. ? d?epaf?
(p.?. G?af???) Composite ??a s???et? ???s? (p.?.
S?ed?as?) Leaf ??a ap?? a?t??e?µe??. ?
composite s?????? e??a? µ?a s???et? d?µ? t?p??
Collection.
36
Composite (S???et?) 5/5
?a??de??µa ?e??? ?st?at?????
37
Visitor (?p?s??pt??) 1/6

• ?at?????a Behavioral
• S??p??
• ???a? t? p??t?p? p?? ep?t??pe? t?? e?t??es?
  ?e????st??
• ?e?t??????? se a?t??e?µe?a µ?a? d?µ??
  a?t??e?µ????.
• ? ?p?s??pt?? ep?t??pe? t?? ???sµ? µ?a? ??a?
  ?e?t?????a? ?????
• ?a a??????? ?? ???se?? t?? a?t??e?µ???? sta ?p??a
  ?a efa?µ?ste?
• a?t? ? ??a ?e?t?????a.
• S?????µa -

38
Visitor (?p?s??pt??) 2/6

• ??te ???s?µ?p??e?ta? ? Visitor
• ?ta? apa?te?ta? ? p??s???? µ?a? ??a? µe??d?? se
  µ?a ?p?????sa
• ?e?a???a ???se?? a??? de? p??pe? ?a
  t??p?p??????? ?? ???se??
• t?? ?e?a???a?.
• ? ??a ?e?t???????t?ta p??st??eta? e????a se µ?a
  ?p????s? (Visitor)
• p?? ???????µe? ap? µ?a af???µ??? ???s?.
• G?a ?a ???p????e? ???s?µ?p??e? t? d?p??
  ap?st??? µ???µat??
• (dual dispatch)
• St? "d?p?? ap?st???" ? ?e?t?????a p??
  e?te?e?ta? e?a?t?ta?
• ap? t? ???µa t?? a?t?s?? ?a?
• t?? t?p? d?? ap?de?t?? (st? s???e???µ??? p??t?p?
  ap? t??
• t?p? t?? Visitor ?a? t?? t?p? t?? st???e???
  p?? ep?s??pteta?).

39
Visitor (?p?s??pt??) 3/6

• Element ????e? µ?a µ???d? accept()
• µe pa??µet?? t? a?t??. visitor.
• ConcreteElement ???p??e? µ?a µ???d? accept() µe
  pa??µet?? t? a?t. visitor.
• Visitor ????e? µ?a ?e?t?????a visit()
• ??a ???e a?t??. ConcreteElement. ??
• ???µa ?a? ? ?p???af? t?? ?e?t?????a?
• d??????? t?? ???s? p?? st???e? t?? p??s???s?.
  ?ts? ? visitor e?e??e?
• st? a?t?st???? a?t??e?µe??.
• ConcreteVisitor ???p??e? ???e ?e?t?????a p??
  ????e? ? visitor ??a
• ???e a?t??e?µe??.
• ObjectStructure (program)
• µp??e? ?a e??a? d?as??des? p??
• ep?t??pe? t?? visitor ?a ?a??se? ta
• a?t??e?µe?a
• - µp??e? ?a e??a? µ?a ??sta ? ??a set

40
Visitor (?p?s??pt??) 4/6
??? ???eta? ? ep?s?e?? - ??s? public µe??d??
(p??sp??as? ap? µ?a ???s? se ????). - St??
visitor ep?s?e?? se ???e ???s? s?µa??e? ???s?
µ?a? µe??d?? t?? accept() p?? ?a ??e? sa?
pa??µet?? t? a?t??. t?? visitor ?a? sa? ep?st??f?
t?? ???s? t?? µe??d?? visit() µe pa??µet?? t??
ea?t? t?? (this). ???ad? ??a ???e a?t??e?µe?? ?a
p??pe? ?a ?a?e?ta? ? µ???d?? public void
accept(Visitor v) v.visit(this) //call
visitor method ??p?? ap?st??? µ???µat??
(dual dispatch) ? µ???d?? accept() µ?s? t??
"d?p??? ap?st????" ?a??d??e? t? ??? t?? e??????
st?? ?at?????? ???s? Visitor ?a? st? s????e?a
st?? e?t??es? t?? ?e?t???????t?ta? st?? ep???µ?t?
a????? ???s?.
41
Visitor (?p?s??pt??) 5/6
?a??de??µa St?? pa?a??t? ???se?? p?? ?a
?e?????µasta? µ?a s?????? ap? p??s?pa (p.?. µ?a
e?t?p?s? t?? ???µ?t??)
42
Visitor (?p?s??pt??) 6/6
?p??tas? s?µpe??f???? (ed? e?t?p?s? t??
d?e????se?? t?? p??s?p??)
43
Observer (?a?at???t??) 1/4
?at?????a Behavioral S??p?? ????e? µ?a s??s?
e???t?s?? ??a-p???-p???? µeta?? a?t??e?µ???? ?ts?
?ste ?ta? µetaß???eta? ? ?at?stas? e???
a?t??e?µ????, ??a ta e?a?t?µe?a a?t??e?µe?a ?a
e??µe?????ta? ?a? ?a t??p?p?????ta? a?t?µata.
S?????µa Dependents, Publish-Subscribe,
Model-View
44
Observer (?a?at???t??) 2/4

• ? s??e??as?a a????ep?d???t?? a?t??e?µ????
  ep?f??e? ?????
• s??e???. ? ?a?at???t?? µe???e? t? s??e???
  µeta?? t??
• a?t??e?µ????.
• ?a s??e??a??µe?a µ??? e??a? d?? t? ?p??e?µe??
  ?a? ?
• pa?at???t?? (s??s? ??a?-p???-p????).
• ?? ?p??e?µe?? d?at??e? ta ded?µ??a, e?? ??
  ?e?t?????e? p??
• af????? t?? pa?at???s? t?? ded?µ????
  ?ata??µeta? se
• a?t??e?µe?a - pa?at???t??.
• ?ta? ??a a?t??e?µe?? a????e? ?at?stas?, t?te
  a?a??????e? p???
• ????? t??? ?ata????µ????? pa?at???t?? t??
  t?????sa a??a??.

45
Observer (?a?at???t??) 3/4
46
Observer (?a?at???t??) 4/4