NSString+Extension warning when creating a NSMutableString from self

NSString+Extension warning when creating a NSMutableString from self

References

Reference NO 1

http://stackoverflow.com/questions/15202116/nsstringextension-warning-when-creating-a-nsmutablestring-from-self

Reference NO 2

http://stackoverflow.com/questions/1749571/what-is-the-purpose-of-having-both-nsmutablestring-and-nsstring

Reference NO 3

http://developer.apple.com/library/ios/documentation/cocoa/conceptual/ProgrammingWithObjectiveC/CustomizingExistingClasses/CustomizingExistingClasses.html

Reference NO 4

http://developer.apple.com/library/ios/documentation/cocoa/conceptual/ProgrammingWithObjectiveC/DefiningClasses/DefiningClasses.html

Reference NO 5

http://www.rubymotion.com/developer-center/guides/runtime/

Reference NO 6

http://www.gnustep.org/resources/documentation/Developer/Base/ProgrammingManual/manual_2.html

Reference NO 7

http://www.otakunozoku.com/objective-c-categories/

Reference NO 8

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