在Objective-C类中混合C函数 [英] Mixing C functions in an Objective-C class

问题描述

我写了一个Objective-C类，但它使用一个用C编写的API。这是很好的，因为混合C调用与Objective-C调用几乎没有问题。

但是，一个API调用需要回调方法（示例）：

  success = CFHostSetClient（host，MyCFHostClientCallBack，& ; context）; 
  

其中 MyCFHostClientCallBack this：

  static void MyCFHostClientCallBack（CFHostRef host，CFHostInfoType typeInfo，const CFStreamError * error，void * info）; 
  

可以/如何调用Objective-C方法

1. 如何将C函数与Objective-C方法混合？
如何将C函数与Objective-C调用混合？

解决方案

混合C和Objective-C方法和函数是可能的，这里是一个简单的例子在iPhone应用中使用SQLite API：（课程网站）

http://stanford.edu/class/cs193p/cgi-bin/drupal/system/files/sample_code/09_MySQLiteTableView.zip

C函数需要在Objective-C（.m）文件中的 @implementation 之外声明。

  int MyCFunction（int num，void * data）
 {
 //代码在这里... 
} 
 
 @实现
 
  - （void）MyObjectiveCMethod：（int）number withData：（NSData *）data 
 {
 // code here 
} 
 
 @end 
  

因为C函数在 @implementation 它不能调用

  [self doSomething] 
  
 
 
 
并且无法访问ivars。
 
 
 
 -back函数接受 userInfo 或上下文类型参数，通常类型为 void * code>。这可以用于将任何Objective-C对象发送到C函数。
 
 
 
如示例代码，这可以使用正常的Objective-C操作来操作。
 
 
 
另外，请阅读这个答案：在Objective-C类中混合C函数 
 
I am writing an Objective-C class but it uses an API written in C. This is mostly fine as mixing C calls with Objective-C calls causes few problems.

However one of the API call requires a call back method (example):
success = CFHostSetClient(host, MyCFHostClientCallBack, &context);
Where MyCFHostClientCallBack is a C function defined like this:
static void MyCFHostClientCallBack(CFHostRef host, CFHostInfoType typeInfo, const CFStreamError *error, void *info);



Can/How do I call an Objective-C method in place of this?
Can/Should I mix C functions with my Objective-C calls?
How do I mix C functions with Objective-C methods?

解决方案
Mixing C and Objective-C methods and function is possible, here is a simple example that uses the SQLite API within an iPhone App: (course site)

http://stanford.edu/class/cs193p/cgi-bin/drupal/system/files/sample_code/09_MySQLiteTableView.zip

C functions need to be declared outside of the @implementation in an Objective-C (.m) file.
int MyCFunction(int num, void *data)
{
     //code here...
}

@implementation

- (void)MyObjectiveCMethod:(int)number withData:(NSData *)data
{
      //code here
}

@end
Because the C function is outside of the @implementation it cannot call methods like 
[self doSomething]
and has no access to ivars.

This can be worked around as long as the call-back function takes a userInfo or context  type parameter, normally of type void*. This can be used to send any Objective-C object to the C function.

As in the sample code, this can be manipulated with normal Objective-C operations.

In addition please read this answer: Mixing C functions in an Objective-C class

                        
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