Question

我正在构建一系列MKPolygons并将它们存储在NSValues数组中：

for (NSDictionary* country in countries) {
    NSMutableArray* polygons = [[NSMutableArray alloc] init];

    for (NSArray* polygon in [country objectForKey:@"polygons"]) {
        CLLocationCoordinate2D polygonCoords[polygon.count];

        int i;
        for (i = 0; i < polygon.count; i++) {
            NSValue* coords = [polygon objectAtIndex:i];
            CLLocationCoordinate2D stored_coords;
            [coords getValue:&stored_coords];
            polygonCoords[i] = stored_coords;
        }

        MKPolygon* poly = [MKPolygon polygonWithCoordinates:polygonCoords count:polygon.count];
        [polygons addObject:[NSValue valueWithBytes:&poly objCType:@encode(MKPolygon)]];
        [chillPillMap addOverlay:poly];
    }
    [country setValue:polygons forKey:@"polygon_objects"];
}

然而，当我稍后尝试访问它们时，我会得到两个或三个并且发生EXC_BAD_ACCESS：

for (NSDictionary* country in countries) {
   NSArray* polygon_objects = [country objectForKey:@"polygon_objects"];
   int i;
   for (i = 0; i < polygon_objects.count; i++) {
        MKPolygon* saved_poly = [MKPolygon alloc];
        [[polygon_objects objectAtIndex:i] getValue:&saved_poly];
   }
}

不知道为什么会这样。

Answer 1

MKPolygon是一个Objective-C对象。您可以将其放入数组而不将其转换为NSValue。此外，您告诉NSValue获取字节的值，但您传递的是指针的地址。坏消息。

为什么不呢......

[polygons addObject:poly]

...然后

MKPolygon *saved_poly = [polygon_objects objectAtIndex:i];

从NSValue获取值的EXC_BAD_ACCESS

1 个答案: