Prototype Design Pattern in Golang - Smartscribs

Prototype Design pattern is a creational design pattern that is used to create a copy of objects while keeping the performance in mind. It ... PrototypeDesignPatterninGolangPublishedbyShubhamonMarch18,2020March18,2020 Inthisseries,wearediscussingDesignPatterns.Inthepreviousarticles,wehavealreadydiscussedtheObjectFactoryDesignPattern, SingletonDesignPattern.andBuilderDesignPattern.Afteralongbreakofaboutamonth,wearebackagaintoexploreandimplementthePrototypeDesignPatterninGolang. PrototypeDesignpatternisa creationaldesignpatternthatisusedtocreateacopyofobjectswhilekeepingtheperformanceinmind.Itspecifiesthekindofobjectstocreateusingprototypicalinstanceandcreatesnewobjectsbycopyingthisprototype. Confusedbytheabovestatement?Letusgoeasy.Pleasenotethatsometimesobjectcreationisacostlyjob.Forexample,ifyoufetcharowfromDatabaseandkeepitasaDAO,itisacostlyaffair.Thegeneralideaoftheprototypedesignpatternishavingasetofobjects(orevenanobject)thatarecreatedatcompile-time,butyouarefreetocreateanynumberofcopiesatruntime.Wejustmutatetheoriginalobjectandsaveittoanewobject.Itsavesusfromrepetitiveobjectcreation. Letusgobacktothedatabaseexample.Wefetchacolumn,andkeepitasaDAO.Nowforeveryfield,wewanttoupdate,wejustmutatetheDAO,insteadofcallingthedatabaseeverytime. Letustakeonemoreexample,Supposeyouhaveanobjectwithalargenumberoffieldsandyouhavetocreateaclone.Thesimplesolutionistoinstantiateanemptyobjectofthesametype,andtheniterateoverallthefieldsandcopyeachfieldfromtheoriginalobjecttotheclonedobject. Apartfrombeingatiringprocess,thereisonemorecatch,sometimesyoujustknowtheinterfaceandnottheexactstructthatisgiventoyou.Undersuchscenariosdeterminingtheexactstructthatisimplementingtheinterfaceandinstantiateanobjectofthattypeinruntimecanbeatediousjob. Allthesetinyproblemsareeasilysolvedwiththehelpofaprototypedesignpattern.Butbeforewebegin,letusunderstandtheterminology: Prototype:Itdeclaresaninterfaceforcloningitself. ConcretePrototype: Itimplementsanoperationforcloningitself. Client:Createsanewobjectbyaskingtheprototypetocloneitself. Implementation WeusethisPrototypeDesignPatterninGolangwhenwewanttocustomizehowanobjectiscloned.Letusseetwoexamplesofcateringtodifferentsituations. Forthefirstscenario,letusbuildautilitythatgivesusadifferentkindofuserobjectasperourneeds.Tobeginwithwehaveastructuserthathasemailandmobileasit’stwoproperties.Wewanttomutatetheobject,withoutaffectingitsoriginalinstance.Thegoalofthiswholeutilityistogeneratedifferentuserobjectswithoutlosingtheflexibilityofcustomizingthemwithoutchangingtheinitialobject.Insimplewords,itisautilitythatcreatesnewuserobject,withthedesiredchanges,justbycopyinganinitialobjectandthenchangingthefieldsofthecopiedobjects,leavingtheoriginalobjectunchanged.   packageprototype typeUserstruct{ emailstring mobilestring } funcNewUser(emailstring,mobilestring)User{ returnUser{ email:email, mobile:mobile, } } //WithEmailcreatesacopyofUserwiththeprovidedemail func(uUser)WithEmail(emailstring)User{ u.email=email returnu } //WithPhonecreatesacopyofUserwiththeprovidedphone func(uUser)WithMobile(mobilestring)User{ u.mobile=mobile returnu } Ifyouobserveclosely,youwillfindthewecallthefunctionsWithEmailandWithUser fromUser(andnot*User).Thus,atthetimewhenthefunctionsarecalled,anewcopyoftheuserobjectismadeandpassedtothefunctions,andallthemutationshappentothecopiedobject.Thisallmayseemnotworththeeffortrightnow,butjustimaginehowusefulitbecomeswhentheobjectinstantiationisacostlyaffair.Inthisutilityweneverinstantiateanobject,wejustcopyanalreadyinstantiatedobjectandmutateisasperourneeds. Nowletuslookattheothercase(whichisinspiredfromhere),thecaseinwhichwearegivenaninterfaceandwedon’texactlyknowwhichstructissatisfyingthatinterface.Letustrydevelopinganobjectmimickingfilesystem. Anyfilesystemhasfilesandfoldersandfoldersitselfcontainfilesandfolders.Eachfile and foldercanberepresentedbya nodeinterface. node interfacealsohasthe clone()function. packagemain typenodeinterface{ print(string) clone()node } Nowletusdefinethetwotypeofentities,filesandfolders. packagemain importfmt typefilestruct{ namestring } func(f*file)print(indstring){ fmt.Println(ind+f.name+"_clone") } func(f*file)clone()node{ return&file{name:f.name} }   packagemain import"fmt" typefolderstruct{ children[]node namestring } func(f*folder)print(indentationstring){ fmt.Println(indentation+f.name+"_clone) for_,i:=rangef.childrens{ i.print(indentation+indentation) } } func(f*folder)clone()node{ cloneFolder:=&folder{name:f.name} vartempChildrens[]node for_,i:=rangef.childrens{ copy:=i.clone() tempChildrens=append(tempChildrens,copy) } cloneFolder.childrens=tempChildrens returncloneFolder } Sincebothfileandfolderstructimplementstheprintandclonefunctions,hencetheyareoftypeinode.Also,noticetheclonefunctioninbothfileandfolder.Theclonefunctioninbothofthemreturnsacopyoftherespectivefileorfolder.Whilecloningweappendthekeyword“_clone”forthenamefield.Let’swritethemainfunctiontotestthingsout. packagemain import"fmt" funcmain(){ file1:=&file{name:"File1"} file2:=&file{name:"File2"} file3:=&file{name:"File3"} folder1:=&folder{ childrens:[]inode{file1}, name:"Folder1", } folder2:=&folder{ childrens:[]inode{folder1,file2,file3}, name:"Folder2", } fmt.Println("\nPrintinghierarchyforFolder2") folder2.print("") cloneFolder:=folder2.clone() fmt.Println("\nPrintinghierarchyforcloneFolder") cloneFolder.print("") }   HereweseehowwecouldcloneaninterfacewithoutknowingtheunderlyingtypeusingthePrototypedesignpatterninGolang. Golanghasaninbuiltmechanismofcloningobjects,andthusyouwouldnotfindalotofusesofthisparticulardesignpattern.However,ifyouwishtoknowaboutthedesignpatterns,thisisjustonemoreflavour. Categories: DesignPatternsGolangTech Tags:DesignPatternsDesignPatternsGolangSystemDesign 0Comments LeaveaReplyCancelreplyYouremailaddresswillnotbepublished.Requiredfieldsaremarked*Name* Email* Website What'sonyourmind?Savemyname,email,andwebsiteinthisbrowserforthenexttimeIcomment. Whatareyoulookingfor? 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