xcode运行react-native报错"_OBJC_CLAS

Undefined symbols for architecture x86_64:

  "_OBJC_CLASS_$_RCTBundleURLProvider", referenced from:

      objc-class-ref in AppDelegate.o

  "_OBJC_CLASS_$_RCTRootView", referenced from:

      objc-class-ref in AppDelegate.o

步骤：1，在终端输入：react-native start

2，回到xcode开发工具后，快捷键shift+command+K 完成项目clean

3，最后重新运行即可。