_ Weak, _ strong, and autorelease usage

When the block version of the container is used as the enumerator, an autoreleasepool is automatically added:

The autorelease object is released at the end of the current runloop iteration, because the system adds the Auto Release pool push and pop in each runloop iteration.

Of course, there is no common for loop or for in loop, so it is more convenient to use the block version enumerator of the new version. When traversing in a for loop produces a large number of autorelease variables, You need to manually add a local autoreleasepool.

[Array enumerateobjectsusingblock: ^ (id obj, nsuinteger idx, bool * Stop) {// surrounded by a local @ autoreleasepool}];

 

 

Weak and strong are a mechanism for iOS to release objects. The objects declared by weak will be released to nil after the original pointer is released;

The following code and output of _ weak and _ strong are provided.

@ Implementation autoreleaseviewcontroller _ weak ID reference;-(void) viewdidload {[Super viewdidload]; @ autoreleasepool {nsstring * STR = [nsstring stringwithformat: @ "XXXXX"]; reference = STR; nslog (@ "str ADDR is % P", STR); nslog (@ "reference ADDR is % P", reference) ;}}-(void) viewwillappear :( bool) animated {[Super viewwillappear: animated]; nslog (@ "reference ADDR is % P", reference); nslog (@ "view will appear reference: % @", reference);}-(void) viewdidappear :( bool) animated {[Super viewdidappear: animated]; nslog (@ "viewdidappear reference: % @", reference );} @ end // output 19:40:34. 480 autorelease [4506: 60b] str addr is 0x8f328902014-11-01 19:40:34. 480 autorelease [4506: 60b] reference ADDR is 0x8f328902014-11-01 19:40:34. 480 autorelease [4506: 60b] reference ADDR is 0x02014-11-01 19:40:34. 481 autorelease [4506: 60b] view will appear reference :( null) 19:40:34. 486 autorelease [4506: 60b] viewdidappear reference: (null)

@ Implementation autoreleaseviewcontroller _ strong ID reference;-(void) viewdidload {[Super viewdidload]; @ autoreleasepool {nsstring * STR = [nsstring stringwithformat: @ "XXXXX"]; reference = STR; nslog (@ "str ADDR is % P", STR); nslog (@ "reference ADDR is % P", reference) ;}}-(void) viewwillappear :( bool) animated {[Super viewwillappear: animated]; nslog (@ "reference ADDR is % P", reference); nslog (@ "view will appear reference: % @", reference);}-(void) viewdidappear :( bool) animated {[Super viewdidappear: animated]; nslog (@ "viewdidappear reference: % @", reference );} @ end // output 19:41:20. 872 autorelease [4669: 60b] str addr is 0x8d42dd02014-11-01 19:41:20. 872 autorelease [4669: 60b] reference ADDR is 0x8d42dd02014-11-01 19:41:20. 873 autorelease [4669: 60b] reference ADDR is 0x8d42dd02014-11-01 19:41:20. 873 autorelease [4669: 60b] view will appear reference: xxxxx2014-11-01 19:41:20. 877 autorelease [4669: 60b] viewdidappear reference: XXXXX

 

_ Weak, _ strong, and autorelease usage