Object Factory Design Pattern in Golang - Smartscribs

Please note the manager is opaque to all the details of how a science student is called. This in some ways is the use-case of the object factory ... ObjectFactoryDesignPatterninGolangPublishedbyShubhamonDecember11,2019 Inthepreviousarticle,wediscussedabouttheSingletondesignpatternanditssampleusage.Inthisarticle,wewilldiscussonemore,ObjectFactoryDesignPatterninGolang.ObjectFactoryisthemostprobablymostuseddesignpatternintheOOPworld.Itdealswithinstantiationandcreationofobjectsandhenceisapartofthecreationaldesignpattern.ThisdesignpatternwasintroducedtousinthefamousbookDesignPatterns:ElementsofReusableObject-OrientedSoftwarebyErichGamma,RichardHelm,RalphJohnson,andJohnVlissides. InFactoryPattern,wecancreatetheobjectwithoutexposingthelogicoftheclientthatiscreatingtheobject.Itisliketheend-userasksforacertainkindofobjectanditisgiventohim,abstractingalltheexplanationastohowtheobjectwasobtained,etc.Letustakeanexampletohelpusunderstanditbetter.Letussupposethereisaschoolwhichhasthreestreams:Science,Arts,andCommerce.OnefinedaythemanageroftheschoolcomesandwishestotalktoastudenteachofaSciencestream.HeisunawareoftheexactlocationoftheclassesoftheSciencestreams.Hejustorderstheheadmaster“Bringme,sciencestudent”. Itisnowtheheadmasterwhogoestotheactualclassandcallsastudenttomeetthemanager.Pleasenotethemanagerisopaquetoallthedetailsofhowasciencestudentiscalled. Thisinsomewaysistheuse-caseoftheobjectfactorypattern.Thestudentistheobjectandtheheadmasteristheobjectfactory.Theuser(manager)justtellstheobjectfactory(headmaster)whichkindofobject(student)itneeds,andtheobjectfactory(headmaster)returnsthesamekindofobject(student). Letusnowlookathowwillitlooklikeincodingterms. funcmain(){ student,err:=factory.GetStudent("Science") student.Talk() } Thefactoryistheheadmaster.ThemanagerasksthemanagertogetastudentandjustgivestheinformationthatthestreamisScience.Factory(headmaster)hidingalltheimplementationdetailsfromthemanager,instantiatestheobjectofagiventype(callsthestudentofSciencestream)andreturns.   Golangdoesnothavetheconceptofclassesandobject,butithasstruct{}andinterfaceswhichmorethanmakeupforit. Letusnowlookstepbystep,howtousethisexampleandimplementtheobjectFactoryDesignPatterninGolang. Thisistheparententity(theparentobjectwhichwillbeinstantiatedthroughout).Thisentitywillhavesomebehaviorsrelatingtoit.ThiscanbeachievedinGolangusinginterfaces.Createaninterfacestudentanddefinesomefunctions(behaviors)toit. typeStudentinterface{ Call() } CreateaScienceStudent,whichisanentitythatimplementsthetypeStudent.WewilljustmakeastructandimplementallthefunctionsoftheStudentinterface. packagefactory typeScienceStudentstruct{} func(s*ScienceStudent)Call(){ fmt.Println("Thisisasciencestudent") } OnsimilargroundsmakeArtStudentandCommerceStudent. packagefactory typeArtStudentstruct{} func(s*ArtStudent)Call(){ fmt.Println("Thisisanartsstudent") } typeCommerceStudentstruct{} func(s*CommerceStudent)Call(){ fmt.Println("Thisisacommercestudent") } Nowwehavedefinedthemainentity(student)andit’sdifferentimplementations.Itistimetodefineafactorythattakesintherequirementfromtheuserandreturnstherightimplementationoftheentity. funcGetStudent(subjectstring)Student{ switchsubject{ case"Science": return&ScienceStudent{} case"Commerce": return&CommerceStudent{} case"Arts": return&ArtStudent{} default: fmt.Println("InvalidSubjectgiven") returnnil } } Letusmakeaclienttodrivethecode. packagemain funcmain(){ student:=factory.GetStudent("Science") student.Call() } Andwewiththesesteps.theclientisnotconcernedwiththeimplementationoftheinternalfunctioningoffetchinganinstanceofacertaintype.Hejustcallsamethodtellingthetypeofentityheneeds.Thisisthebeautyoftheobjectfactorypattern. Wewillcontinueexploringmorepatternsinthelaterpostsofthisseries.Inthemeanwhile,refractoryourprojectsandlookwhereyoucanapplythispattern. 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