why use extern "C"

I see some code like this in iOS project: #ifdef __cplusplus extern "C" { #endif ……….//some function,struct #ifdef __cplusplus } #endif if there is C++ compiler and use C linkage,but if there isn’t C++ compiler then use what? And what is the reason of using this way in code? Thanks!

question about protocol

Hi everyone I get confused in SDWebImage code.The author declare a custom protocol “SDWebImageOperation” and have only a method “- (void)cancel”.Then some class comply with this protocol and implement the method “cancel”.But this protocol does not do anything,why write this way.why not every

button in the class which inherit from UIView

I wirte a class which inherit from UIView to show the view.This view include a button.And how can i implement the respond method of this button.UIView class can’t respond button respond method. ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com)

how can i change the UITabBarItem title's color

Some method deprecated in iOS 7.0, so i want to know a good way to change the UITabBarItem title font color which i want to set. ___ Cocoa-dev mailing list (Cocoa-dev@lists.apple.com) Please do not post admin requests or moderator comments to the