solve Undefined symbols for architecture i386:"_OBJC_CLASS_$_SKPSMTPMessage", referenced from

1.You can get this type of error if your class' .m file is not listed under the "Compile Sources" step of the "Build Phases" tab of your target. Normally Xcode does this for you, but sometimes it loses the plot and you need to add the .m file manually.

To do this:

TargetSettings -> Build Phases -> Compile Sources -> add your .m class ->Build and Run

2.Sometimes those errors appear because some framework is not linked properly. Just check all frameworks in "Link Binary With Libraries" in project's build-phase tab.

3.framework is same as project.release/debug

4.有些库链接的时候要改成.mm文件

“双语播放器”已在app store上架，欢迎大家前去下载（主要用于看电影，学英语，程序员一定要学好英语！）

这里是链接：
https://itunes.apple.com/cn/app/shuang-yu-bo-fang-qi-kan-dian/id950279764?mt=8