Cocoa 结构体和 NSMutableArray

我有一个 NSMutableArray，我正在尝试存储和访问一些结构。我该怎么做呢？ “addObject”给我一个错误，说“addObject 的参数 1 的类型不兼容”。这是一个示例（“in”是 NSFileHandle，“array”是 NSMutableArray）：

//Write points
for(int i=0; i<5; i++) {
    struct Point p;
    buff = [in readDataOfLength:1];
    [buff getBytes:&(p.x) length:sizeof(p.x)];
    [array addObject:p];
}

//Read points
for(int i=0; i<5; i++) {
    struct Point p = [array objectAtIndex:i];
    NSLog(@"%i", p.x);
}

如上所述，NSValue可以使用包装一个简单的结构+value:withObjCType: http://developer.apple.com/mac/library/documentation/cocoa/Reference/Foundation/Classes/NSValue_Class/Reference/Reference.html#//apple_ref/doc/uid/20000177-value_withObjCType_ or -initWithBytes:objCType: http://developer.apple.com/mac/library/documentation/cocoa/Reference/Foundation/Classes/NSValue_Class/Reference/Reference.html#//apple_ref/doc/uid/20000177-initWithBytes_objCType_:

// add:
[array addObject:[NSValue value:&p withObjCType:@encode(struct Point)]];

// extract:
struct Point p;
[[array objectAtIndex:i] getValue:&p];

See the 数量和价值指南 http://developer.apple.com/mac/library/documentation/cocoa/Conceptual/NumbersandValues/Articles/Values.html#//apple_ref/doc/uid/20000174-BAJJHDEG了解更多示例。