সোমবার, ১৮ নভেম্বর, ২০১৩

Inversion of Control



·         IoC GKwU abstract principle hvnv KwZcq software architecture design describe K‡i hvnv‡Z GKwU systemGi flow of control  procedural programming Gi flow of control ‡_‡K Dëv  nq|

An example

·         g‡bKwi Avgv‡`i `ywU class Av‡Q X I Y.


·         KwZcq KvR m¤úbœKivi Rb¨ Y class ‡K X class Gi cÖ‡qvRb|
·         G‡ÿ‡Î mvavibZ Avgiv X class G Avgiv Y class Gi instance  create Kwi Z‡eB  X class  Y class  ‡K use Ki‡Z cvi‡e|
·         wKš‘ cÖkœ n‡jv X class Gi wK really Rvbv `iKvi †h †m Y class use Ki‡Q?
·         Gi e`‡j hw` X class ïaygvÎ Rv‡b †h †m Ggb wKQz use Ki‡Q hvi behavior, methods, properties etc Av‡Q Z‡e Zv wK h‡_ô bq?
·         Bnv Ki‡j DcKvixZv wK?
·         DcKvixZv n‡jv X class Y class Gi Dci dependent _v‡K bv|
·         wKfv‡e Avgiv Zv Ki‡Z cvwi?
·         Y class Gi behavior mg~n‡K GKwU abstract class / Interface G define Kwi Ges Yclass G D³ abstract class / Interface implement Kwi Then X class G D³ abstract class / Interface Gi instance use Kwi Z‡eB Zv m¤¢e|


·         Dc‡iv³ diagram G Avgiv †`L‡Z cvB Y class interface I ‡K implement K‡i Ges X class I Gi GKwU instance use K‡i|
·         G‡ÿ‡Î interesting e¨vcvi n‡jv †h hw`I X class Yclass ‡K use K‡i wKš‘X class Zv m¤ú‡K© AeMZ _v‡K bv| Bnv ïaygvÎ Rv‡b †h Bnv hv use Ki‡Q Zv I interface ‡K implement K‡i‡Q|
·         I interface ‡K implement Kvix classwU †h Y B n‡e Ggb ‡Kvb K_v †bB A, B wKsev C ‡h‡Kvb class n‡Z cv‡i| G‡ÿ‡Î kZ© ïaygvÎ GKwUB Avi Zv n‡jv- class hvnvB nDK bv †Kb Zv Aek¨B interface I ‡K implement Ki‡e|
·         myZivs Avgiv †`L‡Z cvB †h X class Y class Gi Dci dependent bq|

Benefits of Inversion of Control

  • IoC use Gi d‡j X class Y class Gi Dci †Kvb dependency bvB| myZivs Y class G †Kvb change Avm‡j Dnvi †Kvb cÖfve X class G co‡e bv|
  • Unit  test Gi mgq codemg~n‡K mn‡RB isolateKiv hvq|
  • SystemGi component I layermg~n Decouple K‡i d‡j modular system development easier nq|
  • DifferentenvironmentG dependency implementationSwapK‡i|
  • Recompile bv K‡i componentmg~n‡K replaceKiv hvq|
  • ApplicationGi gva¨‡g resource mg~n sharingmechanismprovide K‡i|
  • Alleviates a component from being responsible for managing it's dependencies

Applying Inversion of Control – A sample scenario

·         GLb Avgiv IoC Gi real scenario ‡`L‡ev-
·         Avgv‡`i GKwU class Av‡Q hvi name OrderService . Bnv order mg~n processing Ki‡Z use nq|
·         GB OrderService class G GKwU method Av‡Q hvi name AcceptOrder. GB method wU Order object receive K‡i,validate K‡i (check K‡i Bnv business rule Gi mv‡_ valid wK bv) then hw` valid nq Z‡e OrderDatabase class use K‡i database G save K‡i|


·         OrderService class Gi code wb¤œiƒc-
 
 
publicclassOrderService
{
publicvoidAcceptOrder(Order order)
{
//Domain logic such as validation
 
newOrderDatabase().SaveOrder(order);
}
}
·         Dc‡iv³ code Abyhvqx SaveOrder method call Kivi Rb¨ OrderService class GiAcceptOrder method Gi g‡a¨ OrderDatabase class Gi GKwU new instance create Kiv n‡q‡Q|
·         Gfv‡e OrderDatabase Gi SaveOrder() method call Ki‡j OrderService class OrderDatabase class Gi Dci depend n‡q co‡e| d‡j OrderDatabase class G †Kvb change Avm‡j Dnvi cÖfve OrderService class G co‡e Ges Unit Testing complex n‡q hv‡e|
·         Inversion of Control (IoC) use K‡i Avgiv GB RwUjZv mg~n `~i Ki‡Z cvi‡ev|
·         GB scenario ‡Z Inversion of Control (IoC) use Ki‡Z n‡j Avgv‡`i‡K GKwU interface define Ki‡Z n‡e hvnv‡Z OrderDatabase class G used method mg~‡ni Signature _vK‡e Ges OrderDatabase class ‡K GB interface Øviv inherit Ki‡ev|
·         g‡bKwi D³ interface Gi name IOrderSaver. GB interface Øviv OrderDatabase class ‡K inherit Ki‡ev |
·         Then OrderService class G D³ IOrderSaver interface Gi GKwU instance create Ki‡ev| d‡j OrderService class Gi AcceptOrder()  method OrderDatabase class Gi  instance  Gi e`‡j IOrderSaver interface Gi instance use Ki‡e|



·         d‡j OrderService class OrderDatabaseclass m¤ú‡K© wKQzB Rvb‡e bv|
·         Bnv ïaygvÎ IOrderSaver interface Gi GKwU instance use Ki‡e (nq‡Zv OrderDatabase classwU IOrderSaver interface Gi A‡bK¸‡jv implementation Gi g‡a¨ GKwU implementation)
·         GLb Lye mn‡RB OrderService class order mg~n‡K OrderDatabase class use K‡i Database G Save bv K‡i XmlOrderSaver class use K‡i XML G Save Ki‡Z cvi‡ev| G‡ÿ‡Î OrderService classGi code G †Kvb change Ki‡Z n‡e bv|
·         wKsev database I XML G GK‡Î save Ki‡Z cvi‡e|
·         GQvov Av‡iv variation Avbv hv‡e... ...



·         wKš‘ cÖkœ n‡jv OrderService class wKfv‡e IOrderSaver interface Gi instance cv‡e?
·         GRb¨ KwZcq way Av‡Q| Zvi GKwU way n‡”Q Dependency Injection.

Avgv‡`i cieZ©x Post G Avgiv Dependency Injection wb‡q Av‡jvPbv Ki‡ev|




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