2

我正在阅读 Vrope 的 raynderwilch 教程，我几乎将该教程中的所有代码移植到 C++，但我坚持使用这个函数，我被困住了如何将此函数移植到 cocos2d-x c++？我从来没有进入过目标C，所以不能这样做需要你的帮助

-(VRope *)cutRopeInStick:(VStick *)stick newBodyA:(b2Body*)newBodyA newBodyB:(b2Body*)newBodyB {

// 1-First, find out where in your array the rope will be cut
int nPoint = [vSticks indexOfObject:stick];

// Instead of making everything again you'll just use the arrays of
// sticks, points and sprites you already have and split them

// 2-This is the range that defines the new rope
NSRange newRopeRange = (NSRange){nPoint, numPoints-nPoint-1};

// 3-Keep the sticks in a new array
NSArray *newRopeSticks = [vSticks subarrayWithRange:newRopeRange];

// 4-and remove from this object's array
[vSticks removeObjectsInRange:newRopeRange];

// 5-Same for the sprites
NSArray *newRopeSprites = [ropeSprites subarrayWithRange:newRopeRange];
[ropeSprites removeObjectsInRange:newRopeRange];

// 6-Number of points is always the number of sticks + 1
newRopeRange.length += 1;
NSArray *newRopePoints = [vPoints subarrayWithRange:newRopeRange];
[vPoints removeObjectsInRange:newRopeRange];

// 7-The removeObjectsInRange above removed the last point of
// this rope that now belongs to the new rope. You need to clone
// that VPoint and add it to this rope, otherwise you'll have a
// wrong number of points in this rope
VPoint *pointOfBreak = [newRopePoints objectAtIndex:0];
VPoint *newPoint = [[VPoint alloc] init];
[newPoint setPos:pointOfBreak.x y:pointOfBreak.y];
[vPoints addObject:newPoint];

// 7-And last: fix the last VStick of this rope to point to this new point
// instead of the old point that now belongs to the new rope
VStick *lastStick = [vSticks lastObject];
[lastStick setPointB:newPoint];
[newPoint release];

// 8-This will determine how long the rope is now and how long the new rope will be
float32 cutRatio = (float32)nPoint / (numPoints - 1);

// 9-Fix my number of points
numPoints = nPoint + 1;

// Position in Box2d world where the new bodies will initially be
b2Vec2 newBodiesPosition = b2Vec2(pointOfBreak.x / PTM_RATIO, pointOfBreak.y / PTM_RATIO);

// Get a reference to the world to create the new joint
b2World *world = newBodyA->GetWorld();

// 10-Re-create the joint used in this VRope since bRopeJoint does not allow
// to re-define the attached bodies
b2RopeJointDef jd;
jd.bodyA = joint->GetBodyA();
jd.bodyB = newBodyB;
jd.localAnchorA = joint->GetLocalAnchorA();
jd.localAnchorB = b2Vec2(0, 0);
jd.maxLength = joint->GetMaxLength() * cutRatio;
newBodyB->SetTransform(newBodiesPosition, 0.0);

b2RopeJoint *newJoint1 = (b2RopeJoint *)world->CreateJoint(&jd); //create joint

// 11-Create the new rope joint
jd.bodyA = newBodyA;
jd.bodyB = joint->GetBodyB();
jd.localAnchorA = b2Vec2(0, 0);
jd.localAnchorB = joint->GetLocalAnchorB();
jd.maxLength = joint->GetMaxLength() * (1 - cutRatio);
newBodyA->SetTransform(newBodiesPosition, 0.0);

b2RopeJoint *newJoint2 = (b2RopeJoint *)world->CreateJoint(&jd); //create joint

// 12-Destroy the old joint and update to the new one
world->DestroyJoint(joint);
joint = newJoint1;

// 13-Finally, create the new VRope
VRope *newRope = [[VRope alloc] initWithRopeJoint:newJoint2
                                      spriteSheet:spriteSheet
                                           points:newRopePoints
                                           sticks:newRopeSticks
                                          sprites:newRopeSprites];
return [newRope autorelease];

}

Box2d 部分与 NSRange 相同，请帮助我将其转换为在 cocos2d-x 中使用

在这种情况下，NSRange 和 NSArray 的替代方案是什么？

4

3 回答 3

4

由于 NSRange 只是一个普通的 C 结构，您也可以在 C++ 中简单地定义它：

typedef struct {
    unsigned long location;
    unsigned long length;
} NSRange;
于 2012-10-29T12:45:19.127 回答
1

正如 H2CO3 所说，NSRange 是一个 C 结构，可以轻松定义。

对于 NSArray，您可能最好使用 std::vector< VStick > 之类的东西。

您可以创建一个类似于上述 NSArray 的新数组，如下所示：

std::vector< VStick > newRopeSticks;
newRopeSticks.reserve( range.length );
std::copy( vSticks.begin() + range.Location, vSticks.begin() + range.Location + range.length, std::back_inserter( newRopeSticks ) );

（由于内存错误，我可能有点错误，但这个概念基本上应该可以正常工作）

在回答您的评论时，它不是正确的方法，不。索引不是迭代器。可以取消引用迭代器以将您感兴趣的对象作为一个对象。

您最好使用迭代器范围调用擦除，如下所示：

vSticks.erase( vSticks.begin() + range.Location, vSticks.begin() + range.Location + range.Length );

这将更有效率，因为每次从向量中删除一个元素都会导致它上面的元素被向下复制一个（因为它本质上是一个动态创建的数组）。通过擦除范围，如上所述，它将删除范围内的所有元素，然后复制上面的所有对象。这样做的好处是只复制一次而不是每次擦除。

于 2012-10-29T12:53:02.633 回答
0

我不知道 NSRange 的任何解决方案，但绝对可以使用 cocos2d-x 中的 CCArray 替换 NSArray。

于 2012-10-29T22:45:33.470 回答