Advanced Memory Management Programming Guide.pdf

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1、AdvancedMemoryManagementProgrammingGuideContentsAboutMemoryManagement4AtaGlance4GoodPracticesPreventMemory-RelatedProblems5UseAnalysisToolstoDebugMemoryProblems6MemoryManagementPolicy7BasicMemoryManagementRules7ASimpleExample8UseautoreleasetoSendaDefer

2、redrelease8YouDon’tOwnObjectsReturnedbyReference9ImplementdealloctoRelinquishOwnershipofObjects10CoreFoundationUsesSimilarbutDifferentRules11PracticalMemoryManagement12UseAccessorMethodstoMakeMemoryManagementEasier12UseAccessorMethodstoSetPropertyValue

3、s13Don’tUseAccessorMethodsinInitializerMethodsanddealloc14UseWeakReferencestoAvoidRetainCycles15AvoidCausingDeallocationofObjectsYou’reUsing16Don’tUsedealloctoManageScarceResources17CollectionsOwntheObjectsTheyContain18OwnershipPolicyIsImplementedUsing

4、RetainCounts19UsingAutoreleasePoolBlocks20AboutAutoreleasePoolBlocks20UseLocalAutoreleasePoolBlockstoReducePeakMemoryFootprint21AutoreleasePoolBlocksandThreads23DocumentRevisionHistory242012-07-17

5、Copyright©2012AppleInc.AllRightsReserved.2FiguresPracti

6、calMemoryManagement12Figure1Anillustrationofcyclicalreferences152012-07-17

7、Copyright©2012AppleInc.AllRightsReserved.3AboutMemoryManagementApplicationmemorymanagementistheprocessofallocatingmemoryduringyourprogram’sruntime,usingit,andfreeingitwhenyouare

8、donewithit.Awell-writtenprogramusesaslittlememoryaspossible.InObjective-C,itcanalsobeseenasawayofdistributingownershipoflimitedmemoryresourcesamongmanypiecesofdataandcode.Whenyouhavefinishedworkingthroughthisguide,youwillhavetheknowledgeyouneedtomanage

9、yourapplication’smemorybyexplicitlymanagingthelifecycleofobjectsandfreeingthemwhentheyarenolongerneeded.Althoughmemorymanagementistypicallyconsideredatthelevelofanindividualobject,yourgoalisactuallytomanageobjectgraphs.Youwanttomakesurethatyouhavenomor

10、eobjectsinmemorythanyouactuallyneed.AtaGlanceObjective-Cprovidestwomethodsofapplicationmemorymanagement.2012-07-17

11、Copyright©2012AppleInc.AllRightsReserved.4AboutMemoryManagementAtaGlance1.Inthemethoddescribedinthisguide,referredtoas“ma