{"id":140,"date":"2014-06-16T07:55:45","date_gmt":"2014-06-16T07:55:45","guid":{"rendered":"http:\/\/www.sunyuping.cn\/wordpress\/?p=140"},"modified":"2014-06-16T07:55:45","modified_gmt":"2014-06-16T07:55:45","slug":"ios5-arc-unsafe_unretained%e7%ad%89%e8%af%b4%e6%98%8e","status":"publish","type":"post","link":"https:\/\/www.sunyuping.com\/index.php\/2014\/06\/16\/ios5-arc-unsafe_unretained%e7%ad%89%e8%af%b4%e6%98%8e\/","title":{"rendered":"IOS5 ARC unsafe_unretained\u7b49\u8bf4\u660e"},"content":{"rendered":"

\t\t\t\tiOS5\u4e2d\u52a0\u5165\u4e86\u65b0\u77e5\u8bc6\uff0c\u5c31\u662fARC,\u5176\u5b9e\u6211\u5e76\u4e0d\u662f\u5f88\u559c\u6b22\u5b83\uff0c\u56e0\u4e3a\u4e60\u60ef\u4e86\u81ea\u5df1\u7ba1\u7406\u5185\u5b58\u3002\u4f46\u662f\u5b66\u4e60\u8fd8\u662f\u5f88\u6709\u5fc5\u8981\u7684\u3002<\/p>\n

 <\/p>\n

\u5728iOS\u5f00\u53d1\u8fc7\u7a0b\u4e2d\uff0c\u5c5e\u6027\u7684\u5b9a\u4e49\u5f80\u5f80\u4e0eretain, assign, copy\u6709\u5173\uff0c\u6211\u60f3\u5927\u5bb6\u90fd\u5f88\u719f\u6089\u4e86\uff0c\u5728\u6b64\u6211\u4e5f\u4e0d\u4ecb\u7ecd\uff0c\u7f51\u4e0a\u6709\u5f88\u591a\u76f8\u5173\u6587\u7ae0\u3002<\/p>\n

\u73b0\u5728\u6211\u4eec\u770b\u770biOS5\u4e2d\u65b0\u7684\u5173\u952e\u5b57strong, weak, unsafe_unretained. \u53ef\u4ee5\u4e0e\u4ee5\u524d\u7684\u5173\u952e\u5b57\u5bf9\u5e94\u5b66\u4e60strong\u4e0eretain\u7c7b\u4f3c\uff0cweak\u4e0eunsafe_unretained\u529f\u80fd\u5dee\u4e0d\u591a\uff08\u6709\u70b9\u533a\u522b\uff0c\u7b49\u4e0b\u4f1a\u4ecb\u7ecd\uff0c\u8fd9\u4e24\u4e2a\u65b0\u5173\u952e\u5b57\u4e0eassign\u7c7b\u4f3c\uff09\u3002\u5728iOS5\u4e2d\u7528\u8fd9\u4e9b\u65b0\u7684\u5173\u952e\u5b57\uff0c\u5c31\u53ef\u4ee5\u4e0d\u7528\u624b\u52a8\u7ba1\u7406\u5185\u5b58\u4e86\uff0c\u4ecejava\u7b49\u5176\u5b83\u8bed\u8a00\u8f6c\u8fc7\u6765\u7684\u7a0b\u5e8f\u5458\u975e\u5e38\u53d7\u7528\u3002<\/p>\n

 <\/p>\n

strong\u5173\u952e\u5b57\u4e0eretain\u5173\u4f3c\uff0c\u7528\u4e86\u5b83\uff0c\u5f15\u7528\u8ba1\u6570\u81ea\u52a8\uff0b1\uff0c\u7528\u5b9e\u4f8b\u66f4\u80fd\u8bf4\u660e\u4e00\u5207<\/p>\n

\n
    \n
  1. @property\u00a0(nonatomic,\u00a0strong)\u00a0NSString\u00a0*string1;\u00a0\u00a0\u00a0<\/span><\/li>\n
  2. @property\u00a0(nonatomic,\u00a0strong)\u00a0NSString\u00a0*string2;\u00a0\u00a0<\/span><\/li>\n<\/ol>\n<\/div>\n

     <\/p>\n

    \u6709\u8fd9\u6837\u4e24\u4e2a\u5c5e\u6027\uff0c<\/p>\n

    \n
      \n
    1. @synthesize\u00a0string1;\u00a0\u00a0\u00a0<\/span><\/li>\n
    2. @synthesize\u00a0string2;\u00a0\u00a0<\/span><\/li>\n<\/ol>\n<\/div>\n

       <\/p>\n

      \u731c\u4e00\u4e0b\u4e0b\u9762\u4ee3\u7801\u5c06\u8f93\u51fa\u4ec0\u4e48\u7ed3\u679c\uff1f<\/p>\n

       <\/p>\n

      \n
        \n
      1. self.string1\u00a0=\u00a0@“String\u00a01”<\/span>;\u00a0\u00a0\u00a0<\/span><\/li>\n
      2. self.string2\u00a0=\u00a0self.string1;\u00a0\u00a0\u00a0<\/span><\/li>\n
      3. self.string1\u00a0=\u00a0nil;\u00a0\u00a0<\/span><\/li>\n
      4. NSLog(@“String\u00a02\u00a0=\u00a0%@”<\/span>,\u00a0self.string2);\u00a0\u00a0<\/span><\/li>\n<\/ol>\n<\/div>\n

         <\/p>\n

        \u7ed3\u679c\u662f\uff1aString 2 = String 1<\/p>\n

        \u7531\u4e8estring2\u662fstrong\u5b9a\u4e49\u7684\u5c5e\u6027\uff0c\u6240\u4ee5\u5f15\u7528\u8ba1\u6570\uff0b1\uff0c\u4f7f\u5f97\u5b83\u4eec\u6240\u6307\u5411\u7684\u503c\u90fd\u662f@”String 1″, \u5982\u679c\u4f60\u5bf9retain\u719f\u6089\u7684\u8bdd\uff0c\u8fd9\u7406\u89e3\u5e76\u4e0d\u96be\u3002<\/p>\n

         <\/p>\n

        \u63a5\u7740\u6211\u4eec\u6765\u770bweak\u5173\u952e\u5b57\uff1a<\/p>\n

        \u5982\u679c\u8fd9\u6837\u58f0\u660e\u4e24\u4e2a\u5c5e\u6027\uff1a<\/p>\n

        \n
          \n
        1. @property\u00a0(nonatomic,\u00a0strong)\u00a0NSString\u00a0*string1;\u00a0\u00a0\u00a0<\/span><\/li>\n
        2. @property\u00a0(nonatomic,\u00a0weak)\u00a0NSString\u00a0*string2;\u00a0\u00a0<\/span><\/li>\n<\/ol>\n<\/div>\n

          \u5e76\u5b9a\u4e49<\/p>\n

          \n
            \n
          1. @synthesize\u00a0string1;\u00a0\u00a0\u00a0<\/span><\/li>\n
          2. @synthesize\u00a0string2;\u00a0\u00a0<\/span><\/li>\n<\/ol>\n<\/div>\n

            \u518d\u6765\u731c\u4e00\u4e0b\uff0c\u4e0b\u9762\u8f93\u51fa\u662f\u4ec0\u4e48\uff1f<\/p>\n

            \n
              \n
            1. self.string1\u00a0=\u00a0@“String\u00a01”<\/span>;\u00a0\u00a0\u00a0<\/span><\/li>\n
            2. self.string2\u00a0=\u00a0self.string1;\u00a0\u00a0\u00a0<\/span><\/li>\n
            3. self.string1\u00a0=\u00a0nil;\u00a0\u00a0<\/span><\/li>\n
            4. NSLog(@“String\u00a02\u00a0=\u00a0%@”<\/span>,\u00a0self.string2);\u00a0\u00a0<\/span><\/li>\n<\/ol>\n<\/div>\n

              \u7ed3\u679c\u662f\uff1aString 2 = null<\/p>\n

              \u5206\u6790\u4e00\u4e0b\uff0c\u7531\u4e8eself.string1\u4e0eself.string2\u6307\u5411\u540c\u4e00\u5730\u5740\uff0c\u4e14string2\u6ca1\u6709retain\u5185\u5b58\u5730\u5740\uff0c\u800cself.string1=nil\u91ca\u653e\u4e86\u5185\u5b58\uff0c\u6240\u4ee5string1\u4e3anil\u3002\u58f0\u660e\u4e3aweak\u7684\u6307\u9488\uff0c\u6307\u9488\u6307\u5411\u7684\u5730\u5740\u4e00\u65e6\u88ab\u91ca\u653e\uff0c\u8fd9\u4e9b\u6307\u9488\u90fd\u5c06\u88ab\u8d4b\u503c\u4e3anil\u3002\u8fd9\u6837\u7684\u597d\u5904\u80fd\u6709\u6548\u7684\u9632\u6b62\u91ce\u6307\u9488\u3002\u5728c\/c++\u5f00\u53d1\u8fc7\u7a0b\u4e2d\uff0c\u4e3a\u4f55\u5927\u725b\u90fd\u8bf4\u6307\u9488\u7684\u7a7a\u95f4\u91ca\u653e\u4e86\u540e\uff0c\u90fd\u8981\u5c06\u6307\u9488\u8d4b\u4e3aNULL. \u5728\u8fd9\u513f\u7528weak\u5173\u952e\u5b57\u5e2e\u6211\u4eec\u505a\u4e86\u8fd9\u4e00\u6b65\u3002<\/p>\n

               <\/p>\n

              \u63a5\u7740\u6211\u4eec\u6765\u770bunsafe_unretained<\/p>\n

              \u4ece\u540d\u5b57\u53ef\u4ee5\u770b\u51fa\uff0cunretained\u4e14unsafe\uff0c\u7531\u4e8e\u662funretained\u6240\u4ee5\u4e0eweak\u6709\u70b9\u7c7b\u4f3c\uff0c\u4f46\u662f\u5b83\u662funsafe\u7684\uff0c\u4ec0\u4e48\u662funsafe\u7684\u5462\uff0c\u4e0b\u9762\u770b\u5b9e\u4f8b\u3002<\/p>\n

              \u5982\u679c\u8fd9\u6837\u58f0\u660e\u4e24\u4e2a\u5c5e\u6027\uff1a<\/p>\n

              \u5e76\u5b9a\u4e49<\/p>\n

              \n
                \n
              1. @property\u00a0(nonatomic,\u00a0strong)\u00a0NSString\u00a0*string1;\u00a0\u00a0\u00a0<\/span><\/li>\n
              2. @property\u00a0(nonatomic,\u00a0unsafe_unretained)\u00a0NSString\u00a0*string2;\u00a0\u00a0<\/span><\/li>\n<\/ol>\n<\/div>\n

                \u518d\u6765\u731c\u4e00\u4e0b\uff0c\u4e0b\u9762\u7684\u4ee3\u7801\u4f1a\u6709\u4ec0\u4e48\u7ed3\u679c\uff1f<\/p>\n

                \n
                  \n
                1. self.string1\u00a0=\u00a0@“String\u00a01”<\/span>;\u00a0\u00a0\u00a0<\/span><\/li>\n
                2. self.string2\u00a0=\u00a0self.string1;\u00a0\u00a0\u00a0<\/span><\/li>\n
                3. self.string1\u00a0=\u00a0nil;\u00a0\u00a0<\/span><\/li>\n
                4. NSLog(@“String\u00a02\u00a0=\u00a0%@”<\/span>,\u00a0self.string2);\u00a0\u00a0<\/span><\/li>\n<\/ol>\n<\/div>\n

                  \u8bf7\u6ce8\u610f\uff0c\u5728\u6b64\u6211\u5e76\u6ca1\u6709\u53eb\u4f60\u731c\u4f1a\u6709\u4ec0\u4e48\u8f93\u51fa\uff0c\u56e0\u4e3a\u6839\u672c\u4e0d\u4f1a\u6709\u8f93\u51fa\uff0c\u4f60\u7684\u7a0b\u5e8f\u4f1acrash\u6389\u3002<\/p>\n

                  \u539f\u56e0\u662f\u4ec0\u4e48\uff0c\u5176\u5b9e\u5c31\u662f\u91ce\u6307\u9488\u9020\u6210\u7684\uff0c\u6240\u4ee5\u91ce\u6307\u9488\u662f\u53ef\u6015\u7684\u3002\u4e3a\u4f55\u4f1a\u9020\u6210\u91ce\u6307\u9488\u5462\uff1f\u540c\u4e8e\u7528unsafe_unretained\u58f0\u660e\u7684\u6307\u9488\uff0c\u7531\u4e8eself.string1=nil\u5df2\u5c06\u5185\u5b58\u91ca\u653e\u6389\u4e86\uff0c\u4f46\u662fstring2\u5e76\u4e0d\u77e5\u9053\u5df2\u88ab\u91ca\u653e\u4e86\uff0c\u6240\u4ee5\u662f\u91ce\u6307\u9488\u3002\u7136\u540e\u8bbf\u95ee\u91ce\u6307\u9488\u7684\u5185\u5b58\u5c31\u9020\u6210crash. \u00a0\u6240\u4ee5\u5c3d\u91cf\u5c11\u7528unsafe_unretained\u5173\u952e\u5b57\u3002<\/p>\n

                   <\/p>\n

                  strong,weak,\u00a0unsafe_unretained\u5f80\u5f80\u90fd\u662f\u7528\u6765\u58f0\u660e\u5c5e\u6027\u7684\uff0c\u5982\u679c\u60f3\u58f0\u660e\u4e34\u65f6\u53d8\u91cf\u5c31\u5f97\u7528__strong, \u00a0__weak, __unsafe_unretained, \u00a0__autoreleasing, \u5176\u7528\u6cd5\u4e0e\u4e0a\u9762\u4ecb\u7ecd\u7684\u7c7b\u4f3c\u3002<\/p>\n

                  \u8fd8\u662f\u770b\u770b\u5b9e\u4f8b\u5427\u3002<\/p>\n

                  \n
                    \n
                  1. __strong\u00a0NSString\u00a0*yourString\u00a0=\u00a0@“Your\u00a0String”<\/span>;\u00a0\u00a0\u00a0<\/span><\/li>\n
                  2. __weak\u00a0\u00a0NSString\u00a0*myString\u00a0=\u00a0yourString;\u00a0\u00a0\u00a0<\/span><\/li>\n
                  3. yourString\u00a0=\u00a0nil;\u00a0\u00a0\u00a0<\/span><\/li>\n
                  4. __unsafe_unretained\u00a0NSString\u00a0*theirString\u00a0=\u00a0myString;\u00a0\u00a0<\/span><\/li>\n
                  5. \/\/\u73b0\u5728\u6240\u6709\u7684\u6307\u9488\u90fd\u4e3anil<\/span>\u00a0\u00a0<\/span><\/li>\n<\/ol>\n<\/div>\n

                     <\/p>\n

                    \u518d\u770b\u4e00\u4e2a\uff1a<\/p>\n

                    \n
                      \n
                    1. __strong\u00a0NSString\u00a0*yourString\u00a0=\u00a0@“Your\u00a0String”<\/span>;\u00a0\u00a0\u00a0<\/span><\/li>\n
                    2. __weak\u00a0\u00a0NSString\u00a0*myString\u00a0=\u00a0yourString;\u00a0\u00a0\u00a0<\/span><\/li>\n
                    3. __unsafe_unretained\u00a0NSString\u00a0*theirString\u00a0=\u00a0myString;\u00a0\u00a0<\/span><\/li>\n
                    4. yourString\u00a0=\u00a0nil;\u00a0\u00a0\u00a0<\/span><\/li>\n
                    5. \/\/\u73b0\u5728yourString\u4e0emyString\u7684\u6307\u9488\u90fd\u4e3anil,\u800ctheirString\u4e0d\u4e3anil,\u4f46\u662f\u662f\u91ce\u6307\u9488\u3002<\/span>\u00a0\u00a0<\/span><\/li>\n<\/ol>\n<\/div>\n

                      __autoreleasing\u7684\u7528\u6cd5\u4ecb\u7ecd\uff1a<\/p>\n

                      \u5728c\/c++\uff0cobjective-c\u5185\u5b58\u7ba1\u7406\u4e2d\u6709\u4e00\u6761\u662f\uff1a\u8c01\u5206\u914d\u8c01\u91ca\u653e\u3002\u00a0__autoreleasing\u5219\u53ef\u4ee5\u4f7f\u5bf9\u50cf\u5ef6\u8fdf\u91ca\u653e\u3002\u6bd4\u5982\u4f60\u60f3\u4f20\u4e00\u4e2a\u672a\u521d\u59cb\u5316\u5730\u5bf9\u50cf\u5f15\u7528\u5230\u4e00\u4e2a\u65b9\u6cd5\u5f53\u4e2d\uff0c\u5728\u6b64\u65b9\u6cd5\u4e2d\u5b9e\u59cb\u5316\u6b64\u5bf9\u50cf\uff0c\u90a3\u4e48\u8fd9\u79cd\u60c5\u51b5\u5c06\u662f__autoreleasing\u8868\u6f14\u7684\u65f6\u5019\u3002\u770b\u4e2a\u793a\u4f8b\uff1a<\/p>\n

                      \n
                        \n
                      1. –\u00a0(void<\/span>)\u00a0generateErrorInVariable:(__autoreleasing\u00a0NSError\u00a0**)paramError{\u00a0\u00a0\u00a0<\/span><\/li>\n
                      2. \u00a0\u00a0\u00a0\u00a0NSArray\u00a0*objects\u00a0=\u00a0[[NSArray\u00a0alloc]\u00a0initWithObjects:@“A\u00a0simple\u00a0error”<\/span>,\u00a0nil];\u00a0\u00a0<\/span><\/li>\n
                      3. \u00a0\u00a0\u00a0\u00a0NSArray\u00a0*keys\u00a0=\u00a0[[NSArray\u00a0alloc]\u00a0initWithObjects:NSLocalizedDescriptionKey,\u00a0nil];\u00a0\u00a0<\/span><\/li>\n
                      4. \u00a0\u00a0\u00a0\u00a0NSDictionary\u00a0*errorDictionary\u00a0=\u00a0[[NSDictionary\u00a0alloc]\u00a0initWithObjects:objects\u00a0forKeys:keys];\u00a0\u00a0<\/span><\/li>\n
                      5. \u00a0\u00a0\u00a0\u00a0*paramError\u00a0=\u00a0[[NSError\u00a0alloc]\u00a0initWithDomain:@“MyApp”<\/span>\u00a0code:1\u00a0userInfo:errorDictionary];\u00a0\u00a0<\/span><\/li>\n
                      6. }\u00a0\u00a0<\/span><\/li>\n
                      7. -(void<\/span>)test\u00a0\u00a0<\/span><\/li>\n
                      8. {\u00a0\u00a0<\/span><\/li>\n
                      9. \u00a0\u00a0\u00a0\u00a0NSError\u00a0*error\u00a0=\u00a0nil;\u00a0\u00a0\u00a0<\/span><\/li>\n
                      10. \u00a0\u00a0\u00a0\u00a0[self\u00a0generateErrorInVariable:&error];\u00a0\u00a0<\/span><\/li>\n
                      11. \u00a0\u00a0\u00a0\u00a0NSLog(@“Error\u00a0=\u00a0%@”<\/span>,\u00a0error);\u00a0\u00a0<\/span><\/li>\n
                      12. }\u00a0\u00a0<\/span><\/li>\n<\/ol>\n<\/div>\n

                         <\/p>\n

                        \u8fd9\u6837\u5373\u4fbf\u5728\u51fd\u6570\u5185\u90e8\u7533\u8bf7\u7684\u7a7a\u95f4\uff0c\u5728\u51fd\u6570\u5916\u90e8\u4e5f\u53ef\u4ee5\u4f7f\u7528\uff0c\u540c\u6837\u4e5f\u9002\u5408\u8c01\u5206\u914d\u8c01\u91ca\u653e\u7684\u539f\u5219\u3002<\/p>\n

                        \u540c\u6837\u4e0b\u9762\u7684\u4ee3\u7801\u4e5f\u662f\u7c7b\u4f3c\u539f\u56e0, \u53ea\u4e0d\u8fc7\u5728\u6ca1\u6709\u5f00\u542fARC\u7684\u60c5\u51b5\u4e0b\u9002\u7528\uff1a<\/p>\n

                        \n
                          \n
                        1. -(NSString\u00a0*)stringTest\u00a0\u00a0<\/span><\/li>\n
                        2. {\u00a0\u00a0<\/span><\/li>\n
                        3. \u00a0\u00a0\u00a0\u00a0NSString\u00a0*retStr\u00a0=\u00a0[NSString\u00a0stringWithString:@“test”<\/span>];\u00a0\u00a0<\/span><\/li>\n
                        4. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span><\/li>\n
                        5. \u00a0\u00a0\u00a0\u00a0return<\/span>\u00a0[[retStr\u00a0retain]\u00a0autorelease];\u00a0\u00a0<\/span><\/li>\n
                        6. }\u00a0\u00a0<\/span><\/li>\n<\/ol>\n<\/div>\n

                          \u5f00\u542fARC\u540e\uff0c\u5e94\u6539\u4e3a\uff1a<\/p>\n

                          \n
                            \n
                          1. -(NSString\u00a0*)stringTest\u00a0\u00a0<\/span><\/li>\n
                          2. {\u00a0\u00a0<\/span><\/li>\n
                          3. \u00a0\u00a0\u00a0\u00a0__autoreleasing\u00a0NSString\u00a0*retStr\u00a0=\u00a0[NSString\u00a0alloc]\u00a0initWithString:@“test”<\/span>];\u00a0\u00a0<\/span><\/li>\n
                          4. \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/span><\/li>\n
                          5. \u00a0\u00a0\u00a0\u00a0return<\/span>\u00a0retStr;\u00a0\u00a0<\/span><\/li>\n
                          6. }\u00a0<\/span><\/li>\n<\/ol>\n<\/div>\n","protected":false},"excerpt":{"rendered":"

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