oc中的可变数组NSMutableArray里面只能存放object，对于结构体类型，必须进行转换才能放入可变数组

 NSMutableArray *coordinateArray = [NSMutableArray array];

 CLLocationCoordinate2D coor;

 coor.latitude = item.latitude;

 coor.longitude = item.longitude;

 NSValue *value = [NSValue value:&coor withObjCType:@encode(CLLocationCoordinate2D)];

[coordinateArray addObject:value];