为什么我不能在纯 C 中包含 AppKit，即使我可以自己声明函数? [英] Why I cannot include AppKit in pure C, even though I can declare the functions myself?

问题描述

我想使用更多的 C 和更少的 ObjC 和 Swift 编写一个 MacOS 应用程序.我首先使用 main 函数创建了一个 main.c 文件.接下来是从 main 函数调用 NSApplicationMain.这是在 AppKit 中定义的.但是，当我从 main.c 尝试 #include <AppKit/AppKit.h> 时出现 Could not build module 'AppKit' 错误>.我绕过了这个:

I would like to write a MacOS application using more C and less ObjC and Swift. I started by creating a main.c file with the main function. Next is to call NSApplicationMain from the main function. This is defined in AppKit. However, I get a Could not build module 'AppKit' error when I try #include <AppKit/AppKit.h> from main.c. I circumvented this with:

extern int NSApplicationMain(int argc, const char * _Nonnull *argv);

这奏效了.我的问题是，很明显 NSApplicationMain 可以从 C 中调用，那么为什么我 必须 直接将其 extern 而不是直接包含 AppKit.h ?为什么他们不让您以正确的方式包含它而不是自己声明 NSApplicationMain ?我不应该这样做吗?

This worked. My question is, clearly NSApplicationMain can be called from C so why do I have to extern it directly instead of including AppKit.h directly? Why they do not let you include it the proper way instead of declaring NSApplicationMain yourself? Am I not supposed to do that?

为什么不能这样做:

#include <stdio.h>
#include <AppKit/AppKit.h>
int main(int argc, const char *argv[]) {
    return NSApplicationMain(argc, argv);
}

但是你可以这样做:

#include <stdio.h>
extern int NSApplicationMain(int argc, const char * _Nonnull *argv);
int main(int argc, const char *argv[]) {
    return NSApplicationMain(argc, argv);
}

推荐答案

总之，它不是标准的 C 头文件，虽然它有 .h 扩展名.请注意，即使在 Objective-C .m 文件中，AppKit.h 也必须导入不包含

In short, it is not standard C header file though it has .h extension. Note, that even in Objective-C .m files AppKit.h must be imported not included

#import <AppKit/AppKit.h>

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