"IOS" This class is not a key value coding-compliant for the key ...

In general, this problem is caused by the connection of the interface build to the Iboutlet in the code.

It is possible that the name of the Iboutlet has been modified in the code, resulting in a connection effect in the interface build.

When you hold down Control on the File's Owner and click the mouse, the following screen appears:

Can clearly see the connection situation, the change after the invalid variable will display the cross, need to delete.

Reference: http://www.cnblogs.com/zhulin/archive/2011/05/26/2058014.html

"IOS" This class is not a key value coding-compliant for the key ...