我有一個中期任務，我們為我們課程中的一個程式進行 3 組單元測驗和檔案等。我選擇的程式是物理模擬。
在這個程式中，有兩個類，Thing和World。我能夠獨立創建這些物件。我嘗試通過創建一個Thing來將World物件添加到物件std::vector<Thing> things，然后創建一個函式來添加Thing到vector事物中。但是，當我這樣做時，似乎World物件創建了它自己的副本Thing，因為當我更改Things 位置時，Thingthings 向量中的版本保持不變。
請就此事提供一些指導，我覺得我的問題可能在于我在這種情況下如何使用指標。
void testBoundaryBounce()
{
//Create the world
World world{10.0f, 10.0f, 1.0f};
//Thing, 2 units away from boundary
Thing thing{8.0f, 5.0f, 1.0f};
//Add thing to world (adding it the the things vector)
world.addThing(&thing);
//Apply force that should trigger bounce back to x = 7
thing.applyForce(1.0f, 0.0f);
//Updating thing so that movement takes effect
thing.update();
//Running world update to account for collisions, bounces etc
world.update();
std::cout << "thing x : " << thing.getX() << std::endl;
CPPUNIT_ASSERT(thing.getX() == 7);
}
Thing::Thing(float x, float y, float radius)
: x{x}, y{y}, dX{0}, dY{0}, radius{radius}
{
}
World::World(float width, float height, float gravity)
: width{width}, height{height}, gravity{gravity}
{
std::vector<Thing> things;
}
void World::addThing(Thing* thing)
{
float thingX = thing->getX();
float thingY = thing->getY();
float thingRad = thing->getRad();
std::cout << "Radius : " << thingRad << std::endl;
if (thingX thingRad > width || thingX - thingRad <= 0 || thingY thingRad >
height|| thingY - thingRad <= 0)
{
std::cout << "Thing is out of bounds or is too large" << std::endl;
}
else {
std::cout << "Thing is good" << std::endl;
things.push_back(*thing);
}
}
void World::update()
{
for (Thing& thing : things)
{
thing.update();
float thingX = thing.getX();
float thingY = thing.getY();
float thingRad = thing.getRad();
float worldGrav = this->gravity;
std::cout << "thing x: " << thingX << std::endl;
std::cout << "thing rad: " << thingRad << std::endl;
//World Boundary Bounces
if (thingX thingRad >= width)
{
std::cout << "Bounce left" << std::endl;
thing.applyForce(-2.0f, 0.0f);
thing.update();
}
if (thingX thingRad <= 0)
{
thing.applyForce(2.0f, 0.0f);
thing.update();
std::cout << "Bounce right" << std::endl;
}
if (thingY thingRad >= height)
{
thing.applyForce(0.0f, -2.0f);
thing.update();
std::cout << "Bounce up" << std::endl;
}
if (thingY - thingRad <= 0)
{
thing.applyForce(0.0f, 2.0f);
thing.update();
std::cout << "Bounce down" << std::endl;
}
//Thing Collision Bounces
for (Thing& otherthing : things)
{
float thing2X = otherthing.getX();
float thing2Y = otherthing.getY();
float thing2Rad = otherthing.getRad();
if (thingX thingRad == thing2X thing2Rad && thingY thingRad ==
thing2Y thing2Rad)
{
thing.applyForce(-2.0f, -2.0f);
thing.update();
otherthing.applyForce(2.0f, 2.0f);
otherthing.update();
}
}
//Gravitational Pull
thing.applyForce(0.0f, worldGrav);
}
}
uj5u.com熱心網友回復：
它在...的定義中是正確的void push_back (const value_type& val);
在當前最后一個元素之后，在向量的末尾添加一個新元素。val 的內容被復制（或移動）到新元素。
因此，當您呼叫時things.push_back(*thing);，您正在向“事物”向量添加一個新元素，該元素是thing指標指向的值的副本。
你想改變你的向量來保存指向Thing型別的指標：
std::vector<Thing *> things;
并添加指標而不是副本：
things.push_back(thing);
請注意，您稍后必須通過->而不是訪問欄位.，或者您可以創建對它的參考，例如：
for (Thing* pt: things)
{
Thing& thing = *pt;
thing.update();
//etc...
uj5u.com熱心網友回復：
您可以構造它擁有的s，而不是構造 aThing并將其復制到sworldWorldThing
void testBoundaryBounce()
{
//Create the world
World world{10.0f, 10.0f, 1.0f};
//Thing, 2 units away from boundary
Thing * thing = world.addThing(8.0f, 5.0f, 1.0f);
//Apply force that should trigger bounce back to x = 7
thing->applyForce(1.0f, 0.0f);
//Running world update to account for collisions, bounces etc
//Implies updating all the things
world.update();
std::cout << "thing x : " << thing.getX() << std::endl;
CPPUNIT_ASSERT(thing.getX() == 7);
}
Thing::Thing(float x, float y, float radius)
: x{x}, y{y}, dX{0}, dY{0}, radius{radius}
{
}
World::World(float width, float height, float gravity)
: width{width}, height{height}, gravity{gravity}
{
std::vector<Thing> things;
}
Thing * World::addThing(float x, float y, float radius)
{
std::cout << "Radius : " << radius << std::endl;
if ((x radius > width) || (x - radius <= 0) || (y radius >
height) || (y - radius <= 0))
{
std::cout << "Thing is out of bounds or is too large" << std::endl;
return nullptr;
}
else
{
std::cout << "Thing is good" << std::endl;
return &things.emplace_back(x, y, radius);
}
}
void World::update()
{
for (Thing& thing : things)
{
thing.update();
float thingX = thing.getX();
float thingY = thing.getY();
float thingRad = thing.getRad();
float worldGrav = this->gravity;
std::cout << "thing x: " << thingX << std::endl;
std::cout << "thing rad: " << thingRad << std::endl;
//World Boundary Bounces
if (thingX thingRad >= width)
{
std::cout << "Bounce left" << std::endl;
thing.applyForce(-2.0f, 0.0f);
thing.update();
}
if (thingX thingRad <= 0)
{
thing.applyForce(2.0f, 0.0f);
thing.update();
std::cout << "Bounce right" << std::endl;
}
if (thingY thingRad >= height)
{
thing.applyForce(0.0f, -2.0f);
thing.update();
std::cout << "Bounce up" << std::endl;
}
if (thingY - thingRad <= 0)
{
thing.applyForce(0.0f, 2.0f);
thing.update();
std::cout << "Bounce down" << std::endl;
}
//Thing Collision Bounces
for (Thing& otherthing : things)
{
float thing2X = otherthing.getX();
float thing2Y = otherthing.getY();
float thing2Rad = otherthing.getRad();
if (thingX thingRad == thing2X thing2Rad && thingY thingRad ==
thing2Y thing2Rad)
{
thing.applyForce(-2.0f, -2.0f);
thing.update();
otherthing.applyForce(2.0f, 2.0f);
otherthing.update();
}
}
//Gravitational Pull
thing.applyForce(0.0f, worldGrav);
}
}
順便說一句，每次更新都會自動反彈
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