@在Objective-C2.0中合成C结构数组 我试图在Mac OS X API（音频队列服务）中遵循C++接口的教程，但是在COCOA（实际上，只是基础）应用程序（实际上，只是一个工具）。它的结构如下所示： static const int kNumberBuffers = 3; // 1 struct AQPlayerState { AudioStreamBasicDescription mDataFormat; // 2 AudioQueueRef mQueue; // 3 AudioQueueBufferRef mBuffers[kNumberBuffers]; // 4 AudioFileID mAudioFile; // 5 UInt32 bufferByteSize; // 6 SInt64 mCurrentPacket; // 7 UInt32 mNumPacketsToRead; // 8 AudioStreamPacketDescription *mPacketDescs; // 9 bool mIsRunning; // 10 }; -(void)methodOfOtherClass { PlayerState * playerState = [[PlayerState alloc] init]; AudioQueueBufferRef abc[3] = //something [playerState setMyBuffers:(AudioQueueBufferRef*)abc]; DLog(@"I'm in OtherClass and playerState.myBuffers returns %@, %@, %@", playerState.myBuffers[0],playerState.myBuffers[1],playerState.myBuffers[2]) abc[1] = 6.22; // reassigning one of the values in our local variable playerState.myBuffers = (GLfloat*)abc; //call the setter again, with dot syntax this time if you like DLog(@"I'm in OtherClass and playerState.myBuffers returns %@, %@, %@", playerState.myBuffers[0],playerState.myBuffers[1],playerState.myBuffers[2]) [playerState setMyBuffersA:yourStructA B:yourStructB C:yourStructC]; DLog(@"I'm in OtherClass and playerState.myBuffers returns %@, %@, %@", playerState.myBuffers[0],playerState.myBuffers[1],playerState.myBuffers[2]) }

我在将第4项翻译成Objective-C时遇到了很多麻烦，因为我不知道如何合成C数组。具体地说，这就是我目前的情况：

PlayerState.h

@synthesis buffers

编译失败，如下所示：“错误：合成属性'buffers'的名称必须与兼容的ivar相同，或者必须显式命名ivar”

这显然是因为相应的ivar被命名为

\u buffers

，而不是

buffers

——但这是必要的，因为我不能将属性定义为数组（我可以吗？

@property（assign）*AudioQueueBufferRef buffers

是语法错误）

我如何将ivar定义为一个

AudioQueueBufferRef

结构的数组，或者合成属性，使其引用

\u buffers

数组？

编辑：指出C中的数组与指针不同。（详情请参见）。这可以解释您看到的错误，并且会使我发布的代码出错

在这个问题的背景下，链接到中的建议a，我已经复制了：

// PlayerState.h:
@interface PlayerState : NSObject 
{
    AudioQueueBufferRef           _buffers[3];
}

@property(readonly) AudioQueueBufferRef * buffers;

---

这将允许您访问

缓冲区

，就像它是指向

AuidoQueueBufferRef

对象数组的指针一样。

这里的问题如下：

---

为什么要将结构转换为Objective-C对象？Objective-C是C的一个严格的超集，因此您可以使用Objective-C的给定结构

[EDIT]针对您的评论，编译器正在抱怨

mBuffers

声明，因为有关于静态数组大小的规则。C中的规则比C++中的规则要严格一些。作为一个简单的解决方法，只需更改线路即可

static const int kNumberBuffers = 3;

进入

然后结构应该正确编译（当然，前提是您包含了定义所有正确数据类型的必要头，例如

AudioStreamBasicDescription

，等等）

@synthesis buffers

编译失败，如下所示：“错误：合成属性'buffers'的名称必须与兼容的ivar相同，或者必须显式命名ivar”

尝试：

---

您可以有三个缓冲区IVAR（buffer0、buffer1、buffer2），也可以将其设置为指向AudioQueueBufferRef的指针，并分别分配内存以容纳这三个AudioQueueBufferRef。如果需要可变数量的缓冲区，也可以使用NSArray或NSData

但回到更大的上下文，您可能不需要跟踪AudioQueueBufferRef。如果将所有三个缓冲区排队，则会在音频队列回调中得到指向它们的指针

我有一些音频代码记录和播放音频，它调用AudioQueueAllocateBuffer（）和audioQueueBuffer（），然后几乎忘记了缓冲区

如果您试图为AudioQueue编写Cocoa包装器，请不要这样做

---

编辑：但要回答您最初的问题：不能将数组作为属性，因为它不是“纯Ol”数据类型。请参阅Xcode中Objective-C2.0文档中的“声明的属性”，这是：

我正在为OpenGL应用程序做类似的事情，因为这是一个有用的问题（而且很久没有答案），所以我想转换我的解决方案。请注意，使用NSArray可能不那么费力……但如果您需要改进性能和/或使用基本C（或GL或类似的非对象）类型，这应该会有所帮助。另外，如果我做了一些在OSX中不起作用的事情，请原谅，因为我的代码实际上是针对iPhone的。。。但我相信至少概念是一样的。以下是步骤概要：

将变量声明为指针

使用@private防止外部直接访问

将属性声明为指针，指针将设置为指向传递给setter的任何数组

编写或合成setter和getter方法。我对@synthesis的使用似乎使事情变得混乱，并导致内存泄漏，因此我将遵循“编写您自己的路径”

（我想这是以前文章中缺少的链接）因为您返回的是C数组，所以使用malloc分配内存。init方法可能是实现这一点的好地方，您可以使用dealloc或其他方法调用free（myBuffers），因为您的变量具有适当广泛的作用域

我不知道@synthesis it会为您处理malloc'd变量，但其他人可能有我所缺乏的经验。因此，我只是在写二传手和传手。但请注意，我们仍然可以在接口中看到点语法和@property的普通外观

以下是代码：

在PlayerState.h中：

@interface PlayerState : NSObject {
    AudioStreamBasicDescription   dataFormat;
    AudioQueueRef                 queue;
@private
    AudioQueueBufferRef           *myBuffers;
    // [...]
    @property(assign) AudioStreamBasicDescription   dataFormat;
    @property(assign) AudioQueueRef                 queue;
    @property(assign) AudioQueueBufferRef           *myBuffers;

这将为您提供一个指针和一个属性，后者相当于指针所指示内存的访问器方法。我们将编写自己的访问器，并为指针分配内存，并为指针提供指向的内容

现在在PlayerState.m中：

-(id)init
{
    if (self = [super init]) {
        myBuffers = (AudioQueueBufferRef*)malloc(sizeof(AudioQueueBufferRef) * 3);
        /* memory is allocated. Free it elsewhere. Note that "Leaks" will
        probably falsely flag this, but you can test it in Object Allocations
        and see that it is clearly released. */
    }
    return self;
}

// return an array of structs
-(AudioQueueBufferRef*)myBuffers
{
    // you can check for values, etc here, but basically it all comes down to:
    return myBuffers;
}

    // the setter; there are several ways to write it, depending on what your objective
    -(void)setMyBuffers:(AudioQueueBufferRef*)abc
    {
    int i = 3;
    while (i > 0) {
        i--;
        myBuffers[i] = abc[i];
    }
    //another possible implementation, not tested
    //free(myBuffers);
    //myBuffers = NULL;
    //myBuffers = xyz;
    }

// if you want to set individual attributes, you can have another method like:
-(void)setMyBuffersA:(AudioQueueBufferRef)a B:(AudioQueueBufferRef)b C:(AudioQueueBufferRef)c
{
    myBuffers[0] = a;
    myBuffers[1] = b;
    myBuffers[2] = c;
}

现在您可以从另一个类调用这些函数，如下所示：

static const int kNumberBuffers = 3;                              // 1
struct AQPlayerState {
    AudioStreamBasicDescription   mDataFormat;                    // 2
    AudioQueueRef                 mQueue;                         // 3
    AudioQueueBufferRef           mBuffers[kNumberBuffers];       // 4
    AudioFileID                   mAudioFile;                     // 5
    UInt32                        bufferByteSize;                 // 6
    SInt64                        mCurrentPacket;                 // 7
    UInt32                        mNumPacketsToRead;              // 8
    AudioStreamPacketDescription  *mPacketDescs;                  // 9
    bool                          mIsRunning;                     // 10
};

-(void)methodOfOtherClass
{
    PlayerState * playerState = [[PlayerState alloc] init];
    AudioQueueBufferRef abc[3] = //something

    [playerState setMyBuffers:(AudioQueueBufferRef*)abc];
    DLog(@"I'm in OtherClass and playerState.myBuffers returns %@, %@, %@", playerState.myBuffers[0],playerState.myBuffers[1],playerState.myBuffers[2])

    abc[1] = 6.22; // reassigning one of the values in our local variable
    playerState.myBuffers = (GLfloat*)abc; //call the setter again, with dot syntax this time if you like
    DLog(@"I'm in OtherClass and playerState.myBuffers returns %@, %@, %@", playerState.myBuffers[0],playerState.myBuffers[1],playerState.myBuffers[2])

    [playerState setMyBuffersA:yourStructA B:yourStructB C:yourStructC];
    DLog(@"I'm in OtherClass and playerState.myBuffers returns %@, %@, %@", playerState.myBuffers[0],playerState.myBuffers[1],playerState.myBuffers[2])
}

这对我使用iPhone操作系统和我的openGL类型（承认有点不同）测试没问题。然而，我认为它也会对你有用。您可能需要调整某些内容，或者我在复制和粘贴原始代码时引入了一个小的打字错误。另外，如果您喜欢在编写代码时像我一样记录东西，那么记录缓冲区结构的某些成员可能会更有用，这样可以查看所存在的内容和应该存在的内容

另外，如果您习惯于在使用NSLog包装器编写代码时打印对象，即：

DLog（@“array is%@”，myNSarray）

您将获得<

@interface PlayerState : NSObject {
    AudioStreamBasicDescription   dataFormat;
    AudioQueueRef                 queue;
@private
    AudioQueueBufferRef           *myBuffers;
    // [...]
    @property(assign) AudioStreamBasicDescription   dataFormat;
    @property(assign) AudioQueueRef                 queue;
    @property(assign) AudioQueueBufferRef           *myBuffers;

-(id)init
{
    if (self = [super init]) {
        myBuffers = (AudioQueueBufferRef*)malloc(sizeof(AudioQueueBufferRef) * 3);
        /* memory is allocated. Free it elsewhere. Note that "Leaks" will
        probably falsely flag this, but you can test it in Object Allocations
        and see that it is clearly released. */
    }
    return self;
}

// return an array of structs
-(AudioQueueBufferRef*)myBuffers
{
    // you can check for values, etc here, but basically it all comes down to:
    return myBuffers;
}

    // the setter; there are several ways to write it, depending on what your objective
    -(void)setMyBuffers:(AudioQueueBufferRef*)abc
    {
    int i = 3;
    while (i > 0) {
        i--;
        myBuffers[i] = abc[i];
    }
    //another possible implementation, not tested
    //free(myBuffers);
    //myBuffers = NULL;
    //myBuffers = xyz;
    }

// if you want to set individual attributes, you can have another method like:
-(void)setMyBuffersA:(AudioQueueBufferRef)a B:(AudioQueueBufferRef)b C:(AudioQueueBufferRef)c
{
    myBuffers[0] = a;
    myBuffers[1] = b;
    myBuffers[2] = c;
}

-(void)methodOfOtherClass
{
    PlayerState * playerState = [[PlayerState alloc] init];
    AudioQueueBufferRef abc[3] = //something

    [playerState setMyBuffers:(AudioQueueBufferRef*)abc];
    DLog(@"I'm in OtherClass and playerState.myBuffers returns %@, %@, %@", playerState.myBuffers[0],playerState.myBuffers[1],playerState.myBuffers[2])

    abc[1] = 6.22; // reassigning one of the values in our local variable
    playerState.myBuffers = (GLfloat*)abc; //call the setter again, with dot syntax this time if you like
    DLog(@"I'm in OtherClass and playerState.myBuffers returns %@, %@, %@", playerState.myBuffers[0],playerState.myBuffers[1],playerState.myBuffers[2])

    [playerState setMyBuffersA:yourStructA B:yourStructB C:yourStructC];
    DLog(@"I'm in OtherClass and playerState.myBuffers returns %@, %@, %@", playerState.myBuffers[0],playerState.myBuffers[1],playerState.myBuffers[2])
}