我有一个班级Object2D
,其中包含以下界面:
@class Point2D;
@class Vector2D;
@interface Object2D : NSObject
{
Point2D* position;
Vector2D* vector;
ShapeType figure;
CGSize size;
}
@property (assign) CGSize size;
@property ShapeType figure;
- (Point2D*) position;
- (void)setPosition:(Point2D *)pos;
- (Vector2D*) vector;
- (void)setVector:(Vector2D *)vec;
- (id)initWithPosition:(Point2D*)pos vector:(Vector2D*)vec;
- (void)move:(CGRect)bounds;
- (void)bounce:(CGFloat)boundryNormalAngle;
- (void)draw:(CGContextRef)context;
@end
并实施:
@implementation Object2D
@synthesize size;
@synthesize figure;
- (Point2D*) position
{
return position;
}
- (void)setPosition:(Point2D *)pos
{
if (position != nil) {
[position release];
}
position = pos;
}
- (Vector2D*) vector
{
return vector;
}
- (void)setVector:(Vector2D *)vec
{
if (vector != nil) {
[vec release];
}
vector = vec;
}
...
- (void) dealloc
{
if (position != nil) {
[position release];
}
if (vector != nil) {
[vector release];
}
}
我不会将@synthesize
与position
和vector
一起使用,因为我认为,我必须在更改其值之前释放它们。
我有两个问题:
如果我想获得位置值,这是正确的吗?我会获得对职位或新职位的提及吗?
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* pos2;
pos2 = ball.position; <-- IS THIS CORRECT?
第二个问题:
在将新的值分配给position
和vector
之前,是否需要先释放以前的值?
答案 0 :(得分:3)
如果你使用......
@property (nonatomic, retain) Point2D *position;
和矢量相同,它会为你做保留/释放。 (显然@synthesize他们!)
所以如果你做了以下......
Point2D *newPosition = [[Point2D alloc] init];
[myObject setPosition:newPosition];
[newPosition release];
OR
[myObject setPosition:[[[Point2D alloc] init] autorelease]];
然后将处理保留/释放。您需要在Object2D类中添加dealloc并执行EITHER ....
[position release];
OR
[self setPosition:nil];
两者都会在清理时释放对象。
答案 1 :(得分:0)
我的代码发现错误。正确的setter方法可能是:
- (void)setPosition:(Point2D *)pos
{
[pos retain];
[position release];
position = pos;
}
- (void)setVector:(Vector2D *)vec
{
[vec retain];
[vector release];
vector = vec;
}