Xcode umbrella framework

使用场景，

swift framework 调用 ObjC 代码

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So what is an umbrella framework? Why is it used?

Umbrella frameworks are frameworks which contain frameworks within. This can be used in several situations.

When you are developing a custom network class which require a different parsing logic

or need to implement a custom online payment functionality,

you might create an umbrella framework.

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#ifdef __OBJC__
#import 
#else
#ifndef FOUNDATION_EXPORT
#if defined(__cplusplus)
#define FOUNDATION_EXPORT extern "C"
#else
#define FOUNDATION_EXPORT extern
#endif
#endif
#endif



#import "demux.h"
#import "mux.h"
#import "decode.h"
#import "encode.h"
#import "types.h"
#import "mux_types.h"
#import "format_constants.h"

#import "CGImage+WebP.h"

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umbrella 文件，需要设置为公开

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里面所引用的文件，都要设置为公开，

递归涉及到的，都要设置为公开，

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例如：

不能是项目级别