out_of_range error

[Joren]

hi everyone,

I'm a beginner in SFML, but have some experience with c++.
when i was writing a simple snake game i get "Unhandled exception at 0x75a5c42d in SNAKE 1.0.exe: Microsoft C++ exception: std::out_of_range at memory location 0x0024ef9c.."...
I never had one of these errors before and i don't know how to fix them.

here is my code so far:


Main.cpp:

#include "Snake.h"

int main()
{
	Snake game;
	game.run();
	return 0;
}

Snake.h:

#pragma once
#include <SFML\Graphics.hpp>
#include <vector>

class Snake
{
public:					//constructor + run function
	Snake();
	void run();

 private:					//Window
	sf::RenderWindow mWindow;
	sf::RectangleShape dHead;
	sf::RectangleShape dBody;
	std::vector<sf::RectangleShape> dSnake;
private:
	void processEvents();
	void update();
	void render();

	void handlePlayerInput(sf::Keyboard::Key,bool pressed);

	void updateMovement();
	void setMovementBooleansFalse();
	bool mIsMovingUp,mIsMovingDown,mIsMovingLeft,mIsMovingRight;
	void switchSides();
	sf::Time waitTime;
	void addTailPiece();
	void moveTail();
};

 Snake::Snake() : mWindow(sf::VideoMode(640, 480), "Snake 1.0")
{
	{//head
		dHead.setFillColor(sf::Color::Black);
		dHead.setSize(sf::Vector2f(20.f,20.f));
		dHead.setPosition((mWindow.getSize().x/2),(mWindow.getSize().y/2));
	}
	{//tail
		dBody = dHead;
		dBody.setFillColor(sf::Color::Blue);
	}
	{//snake
		dSnake.push_back(dHead);
	}
	{//food
		mFood = dHead;
		mFood.setFillColor(sf::Color::Red);
		placeFood();
	}
	{//time
		waitTime = sf::milliseconds(140);
	}
}
void Snake::run()
{
	
	while(mWindow.isOpen())
	{
		processEvents();
		update();
		render();
	}
}

void Snake::processEvents()
 {
	 sf::Event sEvent;
	 while(mWindow.pollEvent(sEvent))
	 {
		 switch (sEvent.type)
		{
			case sf::Event::KeyPressed:
				handlePlayerInput(sEvent.key.code,true);
				break;
			case sf::Event::Closed:
				mWindow.close();
				break;

		}
	 }
	 
 }

 void Snake::update()
 {
	 sf::Clock clock;
	clock.restart();
	while(clock.getElapsedTime() <= waitTime)
	{
		processEvents();
	}
	 updateMovement();
	 addTailPiece();
 }

 void Snake::render()
 {
	mWindow.clear(sf::Color::White);
	for(int i = 0; i < dSnake.size(); i++)
	{
		mWindow.draw(dSnake.at(i));
	}
	//mWindow.draw(mFood);
	mWindow.display();
 }

void Snake::handlePlayerInput(sf::Keyboard::Key key,bool isPressed)
 {
	 
	setMovementBooleansFalse();
	if (key == sf::Keyboard::Up)
		mIsMovingUp = isPressed;
	else if (key == sf::Keyboard::Down)
		mIsMovingDown = isPressed;
	else if (key == sf::Keyboard::Left)
		mIsMovingLeft = isPressed;
	else if (key == sf::Keyboard::Right)
		mIsMovingRight = isPressed;
 }

 void Snake::updateMovement()
{
	moveTail();
	sf::Vector2f movement(0.f,0.f);
	if(mIsMovingUp)
		movement.y -= dHead.getSize().x;
	if(mIsMovingDown)
		movement.y += dHead.getSize().x;
	if(mIsMovingLeft)
		movement.x -= dHead.getSize().x;
	if(mIsMovingRight)
		movement.x += dHead.getSize().x;
	dSnake.at(0).move(movement);
	switchSides();
}

 void Snake::setMovementBooleansFalse()
{
				mIsMovingUp = false;
				mIsMovingDown = false;
				mIsMovingLeft = false;
				mIsMovingRight = false;
}

 void Snake::switchSides()
{
	sf::Vector2u j=mWindow.getSize();
	unsigned int a = j.x;
	unsigned int b = j.y;

	sf::Vector2f i=dSnake.at(0).getPosition();
	float x = i.x;
	float y = i.y;

	if(x <= -20.0)
	{
		dSnake.at(0).setPosition(a,y);
	}
	else if(x >= a)
	{
		dSnake.at(0).setPosition(0,y);
	}

	if(y <= -20.0)
	{
		dSnake.at(0).setPosition(x,b);
	}
	else if(y >= b)
	{
		dSnake.at(0).setPosition(x,0);
	}


}

 void Snake::addTailPiece()
 {
	 dSnake.push_back(dBody);
 }

 void Snake::moveTail()
 {
	 for(int i = dSnake.size(); i > 1; i--)
	 {
		 dSnake.at(i--).setPosition(dSnake.at(i-=2).getPosition());
	 }
 }

Please help!
Thank you

[Chervil]

Probably the program is accessing an element outside of the vector.
Line 184:

    for (int i = dSnake.size(); i > 1; i--)

try changing it to

    for (int i = dSnake.size() -1; i >= 1; i--)

Also, the changing of i more than once in the same statement at line 186 gives undefined behaviour:
dSnake.at(i--).setPosition(dSnake.at(i-=2).getPosition());
That statement also risks further out-of-range access. You should change i only in one place, in the for statement at line 184. And take care to access elements only in the range 0 to size-1

[Joren]

Thank you so much for the fast answer!

I've been struggling with this for days, and now finally I can continue my Project.

So, Thank you again!!!