我要初始化两次吗？

@interface Object2D : NSObject
{
    Point2D* position;
    Vector2D* vector;
    FigureType figure;
    CGSize size;
}

@property (assign) Point2D* position;
@property (assign) Vector2D* vector;
@property (assign) CGSize size;

...

@end

@implementation Object2D

@synthesize position;
@synthesize vector;
@synthesize size;

- (id)init
{
    if (self = [super init])
    {
        position = [[Point2D alloc] init];
        vector = [[Vector2D alloc] init];
        size.width = kDefaultSize;
        size.height = kDefaultSize;
    }

    return self;
}

- (void) init
{
    // Create a ball 2D object in the upper left corner of the screen
    // heading down and right
    ball = [[Object2D alloc] init];
    ball.position = [[Point2D alloc] initWithX:0.0 Y:0.0];
    ball.vector = [[Vector2D alloc] initWithX:5.0 Y:4.0];

}

Point2D

Vector2D

@class Vector2D;

@interface Point2D : NSObject
{
    CGFloat X;
    CGFloat Y;
}


@interface Vector2D : NSObject
{
    CGFloat angle;
    CGFloat length;
    Point2D* endPoint;
}