UML Class Diagram Tutorial - Lucidchart

Class diagrams are one of the most useful types of diagrams in UML as they clearly map out the structure of a particular system by modeling its classes, ... PINGDOM_CANARY_STRINGSkiptoContentProductProductCreatepowerfulvisualstoimproveyourideas,projects,andprocesses.OverviewLucidchartoverviewAvisualworkspacefordiagramming,datavisualization,andcollaboration.LucidscaleVisualize,optimize,andunderstandyourcloudarchitecture.IntegrationsConnecttotheappsyourteamusesdaily.PaidplansIndividualTeamEnterpriseGetmoredonewithLucidchart+LucidsparkLearnmoreabouthowtheLucidVisualCollaborationSuiteworkstogetherSolutionsSolutionsWorksmartertosavetimeandsolveproblems.ByteamRemoteteamsCollaborateasateamanytime,anywheretoimproveproductivity.EngineeringPlan,understand,andbuildyournetworkarchitecture.ITSpeedupsecurityreviewsandtroubleshootissuesquickly.OperationsDefine,mapout,andoptimizeyourprocesses.ProductPlanprojects,buildroadmaps,andlaunchproductssuccessfully.SalesAlignyourrevenueteamstoclosebiggerdeals,faster.EducationBringcollaboration,learning,andtechnologytogether.ByneedImproveprocessesIdentifygaps,pinpointinefficiencies,andmitigateriskinyourworkflows.OptimizeorganizationsCreatecustomorgchartstofityourbusiness.VisualizetechnicalsystemsGainvisibilityintoyourexistingtechnology.ReplaceVisioDiagram,share,andinnovatefasterwithLucidchart.ResourcesResourcesHelpfulinsightstogetthemostoutofLucidchart.LearningcampusBlogTemplatesWebinarsSupportCasestudiesDiagramsNewsletterCollaboratewithremoteteamsLucidchartisacollaborativeworkspacethatbringsremoteteamstogetherinrealtime.PricingEnterpriseUMLClassDiagramTutorialWhyuseaUMLdiagram?Iwanttolearnmoreaboutusecasediagramsbecausetheyarenewtome.IwanttocreatemyownusecasediagraminLucidchart.IwanttocreateausecasediagramfromaLucidcharttemplate.ContentsWhatisaclassdiagraminUML?BenefitsofclassdiagramsBasiccomponentsofaclassdiagramClassdiagramexamplesHowtomakeaclassdiagramClassdiagramsareoneofthemostusefultypesofdiagramsinUMLastheyclearlymapoutthestructureofaparticularsystembymodelingitsclasses,attributes,operations,andrelationshipsbetweenobjects.WithourUMLdiagrammingsoftware,creatingthesediagramsisnotasoverwhelmingasitmightappear.Thisguidewillshowyouhowtounderstand,plan,andcreateyourownclassdiagrams.8minutereadDoyouwanttocreateyourownUMLdiagram?TryLucidchart.It'sfast,easy,andtotallyfree.CreateaUMLDiagramWhatisaclassdiagraminUML?TheUnifiedModelingLanguage (UML)canhelpyoumodelsystemsinvariousways.OneofthemorepopulartypesinUMListheclassdiagram.Popularamongsoftwareengineerstodocumentsoftwarearchitecture,classdiagramsareatypeofstructurediagrambecausetheydescribewhatmustbepresentinthesystembeingmodeled. NomatteryourleveloffamiliaritywithUMLorclassdiagrams,ourUMLsoftwareisdesignedtobesimpleandeasytouse. UMLwassetupasastandardizedmodeltodescribeanobject-orientedprogrammingapproach.Sinceclassesarethebuildingblockofobjects,classdiagramsarethebuildingblocksofUML.Thevariouscomponentsinaclassdiagramcanrepresenttheclassesthatwillactuallybeprogrammed,themainobjects,ortheinteractionsbetweenclassesandobjects.  Theclassshapeitselfconsistsofarectanglewiththreerows.Thetoprowcontainsthenameoftheclass,themiddlerowcontainstheattributesoftheclass,andthebottomsectionexpressesthemethodsoroperationsthattheclassmayuse.Classesandsubclassesaregroupedtogethertoshowthestaticrelationshipbetweeneachobject. TheUMLshapelibraryinLucidchartcanhelpyoucreatenearlyanycustomclassdiagramusingourUMLdiagramtool. BenefitsofclassdiagramsClassdiagramsoffer anumberofbenefitsforanyorganization.UseUMLclassdiagramsto: Illustratedatamodelsforinformationsystems,nomatterhowsimpleorcomplex. Betterunderstandthegeneraloverviewoftheschematicsofanapplication. Visuallyexpressanyspecificneedsofasystemanddisseminatethatinformationthroughoutthebusiness. Createdetailedchartsthathighlightanyspecificcodeneededtobeprogrammedandimplementedtothedescribedstructure. Provideanimplementation-independentdescriptionoftypesusedinasystemthatarelaterpassedbetweenitscomponents. DiagrammingisquickandeasywithLucidchart.Startafreetrialtodaytostartcreatingandcollaborating.CreateaUMLDiagramBasiccomponentsofaclassdiagramThestandardclassdiagramiscomposedofthreesections: Uppersection: Containsthenameoftheclass.Thissectionisalwaysrequired,whetheryouaretalkingabouttheclassifieroranobject. Middlesection:Containstheattributesoftheclass.Usethissectiontodescribethequalitiesoftheclass.Thisisonlyrequiredwhendescribingaspecificinstanceofaclass. Bottomsection:Includesclassoperations(methods).Displayedinlistformat,eachoperationtakesupitsownline.Theoperationsdescribehowaclass interactswithdata. Memberaccessmodifiers Allclasseshavedifferentaccesslevelsdependingontheaccessmodifier(visibility).Herearetheaccesslevelswiththeircorrespondingsymbols: Public(+) Private(-) Protected(#) Package(~) Derived(/) Static(underlined) Memberscopes Therearetwoscopesformembers:classifiersandinstances. Classifiersarestaticmemberswhileinstancesarethespecificinstancesoftheclass.IfyouarefamiliarwithbasicOOtheory,thisisn'tanythinggroundbreaking. Additionalclassdiagramcomponents Dependingonthecontext,classesinaclassdiagramcanrepresentthemainobjects,interactionsintheapplication,orclassestobeprogrammed.Toanswerthequestion "WhatisaclassdiagraminUML?" youshouldfirstunderstanditsbasicmakeup. Classes: Atemplateforcreatingobjectsandimplementingbehaviorinasystem.InUML,aclassrepresentsanobjectorasetofobjectsthatshareacommonstructureandbehavior.They'rerepresentedbyarectanglethatincludesrowsoftheclassname,itsattributes,anditsoperations.Whenyoudraw aclassinaclassdiagram,you'reonlyrequiredtofilloutthetoprow—theothersareoptionalifyou'dliketoprovidemoredetail. Name: Thefirstrowinaclassshape. Attributes: Thesecondrowinaclassshape.Eachattributeoftheclassisdisplayedonaseparateline. Methods: Thethirdrowinaclassshape.Alsoknownasoperations,methodsaredisplayedinlistformatwitheachoperationonitsownline. Signals:Symbolsthatrepresentone-way,asynchronouscommunicationsbetweenactiveobjects. Datatypes: Classifiersthatdefinedatavalues.Datatypescanmodelbothprimitivetypesandenumerations. Packages:Shapesdesignedtoorganizerelatedclassifiersinadiagram.Theyaresymbolizedwithalargetabbedrectangleshape. Interfaces: Acollectionofoperationsignaturesand/orattributedefinitionsthat define acohesivesetofbehaviors.Interfacesaresimilartoclasses,exceptthataclasscanhaveaninstanceofitstype,andaninterfacemusthaveatleastoneclasstoimplementit. Enumerations: Representationsofuser-defineddatatypes.Anenumerationincludesgroupsofidentifiersthatrepresentvaluesoftheenumeration. Objects: Instancesofaclassorclasses.Objectscanbeaddedtoaclassdiagramtorepresenteitherconcreteorprototypicalinstances. Artifacts: Modelelementsthatrepresenttheconcreteentitiesinasoftwaresystem,suchasdocuments,databases,executablefiles,softwarecomponents,etc. Interactions Theterm"interactions"referstothevariousrelationshipsandlinksthatcanexistinclassandobjectdiagrams.Someofthemostcommoninteractionsinclude: Inheritance: Theprocessofachildorsub-classtakingonthefunctionalityofaparentorsuperclass,alsoknownasgeneralization.It'ssymbolizedwithastraightconnectedlinewithaclosedarrowheadpointingtowardsthesuperclass. Inthisexample,theobject"Car"wouldinheritalloftheattributes (speed,numbersofpassengers,fuel)andmethods(go(),stop(),changeDirection())oftheparentclass("Vehicle")inadditiontothespecificattributes(modeltype,numberofdoors,automaker)andmethodsofitsownclass(Radio(),windshieldWiper(),ac/heat()).Inheritanceisshowninaclassdiagrambyusingasolidlinewithaclosed,hollowarrow. Bidirectionalassociation: Thedefaultrelationshipbetweentwoclasses.Bothclassesareawareofeachotherandtheirrelationshipwiththeother.Thisassociationisrepresentedbyastraightlinebetweentwoclasses. Intheexampleabove,theCarclassandRoadTripclassareinterrelated.Atoneendoftheline,theCartakesontheassociationof"assignedCar"withthemultiplicityvalueof0..1,sowhentheinstanceofRoadTripexists,itcaneitherhaveoneinstanceofCarassociatedwithitornoCarsassociatedwithit.Inthiscase,aseparateCaravanclasswithamultiplicityvalueof0..*isneededtodemonstratethataRoadTripcouldhavemultipleinstancesofCarsassociatedwithit.SinceoneCarinstancecouldhavemultiple"getRoadTrip"associations—inotherwords,onecarcouldgoonmultipleroadtrips—themultiplicityvalueissetto0..* Unidirectionalassociation: Aslightlylesscommonrelationshipbetweentwoclasses. Oneclassisawareoftheotherandinteractswithit.Unidirectionalassociationismodeledwithastraightconnectinglinethatpointsanopenarrowheadfromtheknowingclasstotheknownclass. Asanexample,onyourroadtripthroughArizona,youmightrunacrossaspeedtrapwhereaspeedcamrecordsyourdrivingactivity,butyouwon'tknowaboutituntilyougetanotificationinthemail.Itisn'tdrawnintheimage,butinthiscase,themultiplicityvaluewouldbe0..*dependingonhowmanytimesyoudrivebythespeedcam. ClassdiagramexamplesCreatingaclassdiagramtomapoutprocessflowsiseasy.ConsiderthetwoexamplesbelowasyoubuildyourownclassdiagramsinUML. Classdiagramforahotelmanagementsystem Aclassdiagramcanshowthe relationshipsbetweeneachobjectinahotelmanagementsystem,includingguestinformation,staffresponsibilities,androomoccupancy.Theexamplebelow providesausefuloverviewofthehotelmanagementsystem.Getstartedonaclassdiagrambyclickingthetemplatebelow. Clickhere tousethistemplate ClassdiagramforanATMsystem ATMsaredeceptivelysimple:althoughcustomersonlyneedtopressafewbuttonstoreceivecash,therearemanylayersofsecuritythatasafeandeffectiveATMmustpassthroughtopreventfraudandprovidevalueforbankingcustomers.ThevarioushumanandinanimatepartsofanATMsystemareillustratedbythiseasy-to-readdiagram—everyclasshasitstitle,andtheattributesarelistedbeneath.Youcanedit,save,andsharethischartbyopeningthedocumentandsigningupforafreeLucidchartaccount. Clickhere tousethistemplate HowtomakeaclassdiagramInLucidchart,creatingaclassdiagramfromscratchissurprisinglysimple.Justfollowthesesteps: Openablankdocumentorstartwithatemplate. EnabletheUMLshapelibrary.OntheleftsideoftheLucidcharteditor,click"Shapes."Onceyou'reintheShapeLibraryManager,check"UML"andclick"Save." Fromthelibrariesyoujustadded,selecttheshapeyouwantanddragitfromthetoolboxtothecanvas. Modeltheprocessflowbydrawinglinesbetweenshapeswhileaddingtext. DiveintothisguideonhowtodrawaclassdiagraminUMLforadditionalinsight.InLucidchart,it'seasytoresizeandstyleanyelement.YoucanevenimportSVGshapesandVisiofilesforacustomsolution.Ifyou'dliketolearnmoreaboutUML,checkoutourtutorial,"WhatIsUML?" AdditionalResourcesHowtoDrawaClassDiagraminUMLTimingDiagramTutorialHowtoDrawaStateMachineDiagraminUMLHowtoDrawaCommunicationDiagraminUMLHowtoDrawanObjectDiagraminUMLHowtoDrawaDeploymentDiagraminUMLHowtoDrawanActivityDiagramHowtoDrawaTimingDiagraminUMLCommunicationDiagramTutorialHowtoDrawaSequenceDiagraminUMLClassdiagramsareoneofthemostcommontypesofdiagramsinUML,andLucidcharthasmadeiteasytounderstandandcreatethem.Jumprightintooneofourtemplates,importanexistingclassdiagramandcontinueworkingonitwithinLucidchart,orstartfromscratch.Wehaveallthefeaturesandtoolsyouneedtogetstarted. DoyouwanttocreateyourownUMLdiagram?TryLucidchart.It'sfast,easy,andtotallyfree.CreateaUMLDiagram