如何在C中纯粹编写iOS应用程序

本文翻译自：How to write iOS app purely in C

I read here Learn C Before Objective-C? 我在这里读到在Objective-C之前学习C？

Usually I then replace some Obj-C code with pure C code (after all you can mix them as much as you like, the content of an Obj-C method can be entirely, pure C code) 通常我会用纯C代码替换一些Obj-C代码（毕竟你可以根据需要混合它们，Obj-C方法的内容可以完全是纯C代码）

Is this true? 这是真的？

Is it possible to build an iPhone app purely in the C programming language? 是否有可能纯粹使用C编程语言构建iPhone应用程序？

#1楼

参考：https://stackoom.com/question/hAry/如何在C中纯粹编写iOS应用程序

#2楼

Objective-C is a superset of the C-language, so it is theoretically possible to write a program entirely in C, however, unless you are thoroughly versed in OpenGL ES , You'll need to do at least some objC ( Even Rich's sample has a const NSString* in it ), else you'll have to write the views yourself. Objective-C是C语言的超集，因此理论上可以用C语言编写程序，但是，除非你精通OpenGL ES ，否则你至少需要做一些 objC（ Even Rich的样本）其中有一个const NSString * ，否则你必须自己编写视图。

OK, the above is completely wrong. 好的，以上是完全错误的。 Let me say, I'm astounded Rich achieved this lofty goal, so I ported it over to the mac (source here ). 让我说，我很震惊Rich实现了这个崇高的目标，所以我把它移植到了mac（来源这里）。 The files below have no headers, do not link to Cocoa, nor does the project have a nib: 下面的文件没有标题，不链接到Cocoa，项目也没有nib：

AppDelegate.m AppDelegate.m

#include <objc/runtime.h>
#include <objc/message.h>extern id NSApp;struct AppDel
{Class isa;//Will be an NSWindow later, for now, it's id, because we cannot use pointers to ObjC classesid window;
};// This is a strong reference to the class of the AppDelegate
// (same as [AppDelegate class])
Class AppDelClass;BOOL AppDel_didFinishLaunching(struct AppDel *self, SEL _cmd, id notification) {//alloc NSWindowself->window = objc_msgSend(objc_getClass("NSWindow"),sel_getUid("alloc"));//init NSWindow//Adjust frame.  Window would be about 50*50 px without this//specify window type.  We want a resizeable window that we can close.//use retained backing because this thing is small anyhow//return no because this is the main window, and should be shown immediatelyself->window = objc_msgSend(self->window,sel_getUid("initWithContentRect:styleMask:backing:defer:"),(NSRect){0,0,1024,460}, (NSTitledWindowMask|NSClosableWindowMask|NSResizableWindowMask|NSMiniaturizableWindowMask),NSBackingStoreRetained,NO);//send alloc and init to our view class.  Love the nested objc_msgSends!id view = objc_msgSend(objc_msgSend(objc_getClass("View"), sel_getUid("alloc")), sel_getUid("initWithFrame:"), (struct CGRect) { 0, 0, 320, 480 });// here we simply add the view to the window.objc_msgSend(self->window, sel_getUid("setContentView:"), view);objc_msgSend(self->window, sel_getUid("becomeFirstResponder"));//makeKeyOrderFront: NSWindow to show in bottom left corner of the screenobjc_msgSend(self->window,sel_getUid("makeKeyAndOrderFront:"),self);return YES;
}static void initAppDel()
{//Our appDelegate should be NSObject, but if you want to go the hard route, make this a class pair of NSApplication and try initing those awful delegate methods!AppDelClass = objc_allocateClassPair((Class)objc_getClass("NSObject"), "AppDelegate", 0);//Change the implementation of applicationDidFinishLaunching: so we don't have to use ObjC when this is called by the system.class_addMethod(AppDelClass,sel_getUid("applicationDidFinishLaunching:"),(IMP) AppDel_didFinishLaunching, "i@:@");objc_registerClassPair(AppDelClass);
}void init_app(void)
{objc_msgSend(objc_getClass("NSApplication"),sel_getUid("sharedApplication"));if (NSApp == NULL){fprintf(stderr,"Failed to initialized NSApplication...  terminating...\n");return;}id appDelObj = objc_msgSend(objc_getClass("AppDelegate"),sel_getUid("alloc"));appDelObj = objc_msgSend(appDelObj, sel_getUid("init"));objc_msgSend(NSApp, sel_getUid("setDelegate:"), appDelObj);objc_msgSend(NSApp, sel_getUid("run"));
}//there doesn't need to be a main.m because of this little beauty here.
int main(int argc, char** argv)
{//Initialize a valid app delegate object just like [NSApplication sharedApplication];initAppDel();//Initialize the run loop, just like [NSApp run];  this function NEVER returns until the app closes successfully.init_app();//We should close acceptably.return EXIT_SUCCESS;
}

View.m View.m

#include <objc/runtime.h>
#include <objc/message.h>
#include <ApplicationServices/ApplicationServices.h>// This is a strong reference to the class of our custom view,
// In case we need it in the future.
Class ViewClass;// This is a simple -drawRect implementation for our class. We could have
// used a UILabel  or something of that sort instead, but I felt that this
// stuck with the C-based mentality of the application.
void View_drawRect(id self, SEL _cmd, CGRect rect)
{//make a red NSColor object with its convenience methodid red  = objc_msgSend(objc_getClass("NSColor"), sel_getUid("redColor"));// fill target rect with red, because this is it!NSRect rect1 = NSMakeRect ( 21,21,210,210 );objc_msgSend(red, sel_getUid("set"));NSRectFill ( rect1 );
}// Once again we use the (constructor) attribute. generally speaking,
// having many of these is a very bad idea, but in a small application
// like this, it really shouldn't be that big of an issue.
__attribute__((constructor))
static void initView()
{// Once again, just like the app delegate, we tell the runtime to// create a new class, this time a subclass of 'UIView' and named 'View'.ViewClass = objc_allocateClassPair((Class) objc_getClass("NSView"), "View", 0);// and again, we tell the runtime to add a function called -drawRect:// to our custom view. Note that there is an error in the type-specification// of this method, as I do not know the @encode sequence of 'CGRect' off// of the top of my head. As a result, there is a chance that the rect// parameter of the method may not get passed properly.class_addMethod(ViewClass, sel_getUid("drawRect:"), (IMP) View_drawRect, "v@:");// And again, we tell the runtime that this class is now valid to be used.// At this point, the application should run and display the screenshot shown below.objc_registerClassPair(ViewClass);
}

prefix.pch prefix.pch

//
// Prefix header for all source files of the 'CBasedMacApp' target in the 'CBasedMacApp' project
//#ifdef __OBJC__
#import <Foundation/Foundation.h>
#import <AppKit/AppKit.h>
#endif

#3楼

Damn, it took me a while but I got it: 该死的，我花了一段时间，但我得到了它：

main.c: main.c中：

#include <CoreFoundation/CoreFoundation.h>#include <objc/runtime.h>
#include <objc/message.h>// This is a hack. Because we are writing in C, we cannot out and include
// <UIKit/UIKit.h>, as that uses Objective-C constructs.
// however, neither can we give the full function declaration, like this:
// int UIApplicationMain (int argc, char *argv[], NSString *principalClassName, NSString *delegateClassName);
// So, we rely on the fact that for both the i386 & ARM architectures,
// the registers for parameters passed in remain the same whether or not
// you are using VA_ARGS. This is actually the basis of the objective-c
// runtime (objc_msgSend), so we are probably fine here,  this would be
// the last thing I would expect to break.
extern int UIApplicationMain(int, ...);// Entry point of the application. If you don't know what this is by now,
// then you probably shouldn't be reading the rest of this post.
int main(int argc, char *argv[])
{// Create an @autoreleasepool, using the old-stye API. // Note that while NSAutoreleasePool IS deprecated, it still exists // in the APIs for a reason, and we leverage that here. In a perfect // world we wouldn't have to worry about this, but, remember, this is C.id autoreleasePool = objc_msgSend(objc_msgSend(objc_getClass("NSAutoreleasePool"), sel_registerName("alloc")), sel_registerName("init"));// Notice the use of CFSTR here. We cannot use an objective-c string // literal @"someStr", as that would be using objective-c, obviously.UIApplicationMain(argc, argv, nil, CFSTR("AppDelegate"));objc_msgSend(autoreleasePool, sel_registerName("drain"));
}

AppDelegate.c: AppDelegate.c：

#import <objc/runtime.h>
#import <objc/message.h>// This is equivalent to creating a @class with one public variable named 'window'.
struct AppDel
{Class isa;id window;
};// This is a strong reference to the class of the AppDelegate
// (same as [AppDelegate class])
Class AppDelClass;// this is the entry point of the application, same as -application:didFinishLaunchingWithOptions:
// note the fact that we use `void *` for the 'application' and 'options' fields, as we need no reference to them for this to work. A generic id would suffice here as well.
BOOL AppDel_didFinishLaunching(struct AppDel *self, SEL _cmd, void *application, void *options)
{// we +alloc and -initWithFrame: our window here, so that we can have it show on screen (eventually).// this entire method is the objc-runtime based version of the standard View-Based application's launch code, so nothing here really should surprise you.// one thing important to note, though is that we use `sel_getUid()` instead of @selector().// this is because @selector is an objc language construct, and the application would not have been created in C if I used @selector.self->window = objc_msgSend(objc_getClass("UIWindow"), sel_getUid("alloc"));self->window = objc_msgSend(self->window, sel_getUid("initWithFrame:"), (struct CGRect) { 0, 0, 320, 480 });// here, we are creating our view controller, and our view. note the use of objc_getClass, because we cannot reference UIViewController directly in C.id viewController = objc_msgSend(objc_msgSend(objc_getClass("UIViewController"), sel_getUid("alloc")), sel_getUid("init"));// creating our custom view class, there really isn't too much // to say here other than we are hard-coding the screen's bounds, // because returning a struct from a `objc_msgSend()` (via // [[UIScreen mainScreen] bounds]) requires a different function call// and is finicky at best.id view = objc_msgSend(objc_msgSend(objc_getClass("View"), sel_getUid("alloc")), sel_getUid("initWithFrame:"), (struct CGRect) { 0, 0, 320, 480 });// here we simply add the view to the view controller, and add the viewController to the window.objc_msgSend(objc_msgSend(viewController, sel_getUid("view")), sel_getUid("addSubview:"), view);objc_msgSend(self->window, sel_getUid("setRootViewController:"), viewController);// finally, we display the window on-screen.objc_msgSend(self->window, sel_getUid("makeKeyAndVisible"));return YES;
}// note the use of the gcc attribute extension (constructor).
// Basically, this lets us run arbitrary code before program startup,
// for more information read here: http://stackoverflow.com/questions/2053029
__attribute__((constructor))
static void initAppDel()
{// This is objc-runtime gibberish at best. We are creating a class with the // name "AppDelegate" that is a subclass of "UIResponder". Note we do not need// to register for the UIApplicationDelegate protocol, that really is simply for // Xcode's autocomplete, we just need to implement the method and we are golden.AppDelClass = objc_allocateClassPair(objc_getClass("UIResponder"), "AppDelegate", 0);// Here, we tell the objc runtime that we have a variable named "window" of type 'id'class_addIvar(AppDelClass, "window", sizeof(id), 0, "@");// We tell the objc-runtime that we have an implementation for the method// -application:didFinishLaunchingWithOptions:, and link that to our custom // function defined above. Notice the final parameter. This tells the runtime// the types of arguments received by the function.class_addMethod(AppDelClass, sel_getUid("application:didFinishLaunchingWithOptions:"), (IMP) AppDel_didFinishLaunching, "i@:@@");// Finally we tell the runtime that we have finished describing the class and // we can let the rest of the application use it.objc_registerClassPair(AppDelClass);
}

View.c View.c

#include <objc/runtime.h>// This is a strong reference to the class of our custom view,
// In case we need it in the future.
Class ViewClass;// This is a simple -drawRect implementation for our class. We could have
// used a UILabel  or something of that sort instead, but I felt that this
// stuck with the C-based mentality of the application.
void View_drawRect(id self, SEL _cmd, struct CGRect rect)
{// We are simply getting the graphics context of the current view, // so we can draw to itCGContextRef context = UIGraphicsGetCurrentContext();// Then we set it's fill color to white so that we clear the background.// Note the cast to (CGFloat []). Otherwise, this would give a warning//  saying "invalid cast from type 'int' to 'CGFloat *', or // 'extra elements in initializer'. Also note the assumption of RGBA.// If this wasn't a demo application, I would strongly recommend against this,// but for the most part you can be pretty sure that this is a safe move // in an iOS application.CGContextSetFillColor(context, (CGFloat []){ 1, 1, 1, 1 });// here, we simply add and draw the rect to the screenCGContextAddRect(context, (struct CGRect) { 0, 0, 320, 480 });CGContextFillPath(context);// and we now set the drawing color to red, then add another rectangle// and draw to the screenCGContextSetFillColor(context, (CGFloat []) { 1, 0, 0, 1 });CGContextAddRect(context, (struct CGRect) { 10, 10, 20, 20 });CGContextFillPath(context);
}// Once again we use the (constructor) attribute. generally speaking,
// having many of these is a very bad idea, but in a small application
// like this, it really shouldn't be that big of an issue.
__attribute__((constructor))
static void initView()
{// Once again, just like the app delegate, we tell the runtime to // create a new class, this time a subclass of 'UIView' and named 'View'.ViewClass = objc_allocateClassPair(objc_getClass("UIView"), "View", 0);// and again, we tell the runtime to add a function called -drawRect: // to our custom view. Note that there is an error in the type-specification// of this method, as I do not know the @encode sequence of 'CGRect' off // of the top of my head. As a result, there is a chance that the rect // parameter of the method may not get passed properly.class_addMethod(ViewClass, sel_getUid("drawRect:"), (IMP) View_drawRect, "v@:");// And again, we tell the runtime that this class is now valid to be used. // At this point, the application should run and display the screenshot shown below.objc_registerClassPair(ViewClass);
}

It's ugly, but it works. 这很难看，但它确实有效。

If you would like to download this, you can get it from my dropbox here 如果您想下载此内容，可以在此处从我的保管箱中获取

You can get it from my GitHub repository here : 你可以从我的GitHub库得到它在这里：

#4楼

I read here Learn C Before Objective-C? 我在这里读到在Objective-C之前学习C？

Usually I then replace some Obj-C code with pure C code (after all you can mix them as much as you like, the content of an Obj-C method can be entirely, pure C code) 通常我会用纯C代码替换一些Obj-C代码（毕竟你可以根据需要混合它们，Obj-C方法的内容可以完全是纯C代码）

Is this true? 这是真的？

Could I build an iPhone app purely in the C programming language? 我可以纯粹用C编程语言构建一个iPhone应用程序吗？

The quoted passage is true, but the answer to your question is no. 引用的段落是正确的，但你的问题的答案是否定的。

To illustrate what answerer Mecki on that other question was talking about: 为了说明Mecki对另一个问题的回答：

- (void) drawRect:(CGRect)dirtyRect { //Objective-CCGContextRef context = UIGraphicsGetCurrentContext();  //CCGContextSetRGBFillColor(context, 1.0, 0.0, 0.0, 1.0); //CCGContextFillRect(context, dirtyRect);                 //C} //Objective-C (balances above “- (void) drawRect:…” line)

There is nothing but pure C code within this method, but the method itself is Objective-C code, as is the class that contains this method. 没有什么，但纯C代码，在此方法中，但该方法本身是Objective-C代码，如包含此方法的类。

So it is possible to do what Mecki said, but you can't (practically—as Richard J. Ross III showed, it's technically possible but quite a lot of typing) write a whole Cocoa Touch program in pure C. 所以有可能做到Mecki所说的，但你不能（实际上 - 正如理查德J.罗斯三世所展示的那样，技术上可行，但很多打字）在纯C中编写了一个完整的Cocoa Touch程序。

#5楼

Actually, some of the code posted here, while written in C, is still calling objective-C code :). 实际上，这里发布的一些代码，用C语言编写，仍然是调用Objective-C代码:)。 I don't know if that actually fits the scenario from the original poster when he asked 当他问道时，我不知道这是否真的符合原始海报的情景

Is it possible to build an iPhone app purely in the C programming language? 是否有可能纯粹使用C编程语言构建iPhone应用程序？

but I would agree with the people saying that, generally speaking and for an app with a GUI, you would need to write your GUI in OpenGL (which is C). 但我同意人们的说法，一般而言，对于带有GUI的应用程序，您需要在OpenGL中编写GUI（即C）。

I think that is what most games do, right? 我认为大多数游戏都是这样，对吧？ Although I'm not sure if there's access to the iPhone's I/O (the touchscreen for example) in C. 虽然我不确定是否可以在C中访问iPhone的I / O（例如触摸屏）。

Last but not least, the guys that wrote the code above rock! 最后但并非最不重要的是，编写上面代码的人摇滚！ :) :)

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如何在C中纯粹编写iOS应用程序

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