IOS成长之路-Xcode cannot run using the selected device. 解决办法

   PROJECT --> Info --> Deployment Target --> IOS Deployment Target  里面的值 要设置为  <=真机系统版本

   TARGETS --> Summary --> IOS Application Target --> Deployment Target  里面的值 要设置为 <=真机系统版本

  也要查看一下这两个是否正确

  PROJECT --> Build Settings --> Deployment --> IOS Deployment Target  

  TARGETS --> Build Settings --> Deployment --> IOS Deployment Target 

原因：手机的sdk是4.2.1.编译项目的SDK选的是4.3.

IOS Deployment Target改成4.0就好了。