亲测成功。

随便新建一个swift文件，xcode问是否生成xxx-Bridging-Header.h文件，点YES。再编译，问题解决。

By default, the generated header contains interfaces for Swift declarations marked with the public modifier. It also contains those marked with the internal modifier if your app target has an Objective-C bridging header.

https://developer.apple.com/library/prerelease/ios/documentation/Swift/Conceptual/BuildingCocoaApps/MixandMatch.html#//apple_ref/doc/uid/TP40014216-CH10-XID_84