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Vector iterator not derefranceable

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Hello, I am working on an animation class that has one std::vectors of textures for both a left and right direction of textures. The point of this class it to hold the different frames and then after a specific amount of time has passed, update the frame and then return a texture for rendering. When I compile the code I get this window(attacked file). Here is the animation class:




#include <SFML/Graphics.hpp>
#include <vector>

enum DIRECTION{LEFT = 1, RIGHT = 0};

class Animation{

	void setAnimation(sf::Image sheet, sf::Vector2f frameSize);
	void setDirection(DIRECTION dir);
	void update(sf::Time deltaT);

	sf::Texture& getCurrentFrame(){return *m_Iter;}

	sf::Image m_sfSpriteSheet;
	sf::Vector2f m_sfFrameSize;
	std::vector<sf::Texture> m_LeftFrames;
	std::vector<sf::Texture> m_RightFrames;
	std::vector<sf::Texture>::iterator m_Iter;
	int m_iXFrames , m_iYFrames, m_iCurrentFrame;
	DIRECTION m_CurrentDirection;
	sf::Time m_sfFrameTime;




#include "Animation.hpp"

Animation::Animation() : m_CurrentDirection(LEFT), m_sfFrameTime(sf::seconds(0)){}


void Animation::setAnimation(sf::Image sheet, sf::Vector2f frameSize){

	m_sfSpriteSheet = sheet;
	m_sfFrameSize = frameSize;

	//get the size of the sheet so I can set the vector of texures
	m_iYFrames = (int)(m_sfSpriteSheet.getSize().y / m_sfFrameSize.y);
	m_iXFrames = (int)(m_sfSpriteSheet.getSize().x / m_sfFrameSize.x);

	sf::Texture tempTex;

	//split up sheet
	for(int y = 0; y < m_iYFrames; ++y){

		for(int x = 0; x < m_iXFrames; ++x){

			tempTex.loadFromImage(m_sfSpriteSheet, sf::IntRect((int)(x * m_sfFrameSize.x), (int)(y * m_sfFrameSize.y), 
				                  (int)(m_sfFrameSize.x), (int)(m_sfFrameSize.y)));

			if(y == 0) m_LeftFrames.push_back(tempTex);
			if(y == 1) m_RightFrames.push_back(tempTex);

	*m_Iter = m_LeftFrames[0];

void Animation::setDirection(DIRECTION dir){

	m_CurrentDirection = dir;
	m_iCurrentFrame = 0;

	if(m_CurrentDirection == LEFT) *m_Iter = m_LeftFrames[m_iCurrentFrame];
	if(m_CurrentDirection == RIGHT) *m_Iter = m_RightFrames[m_iCurrentFrame];


void Animation::update(sf::Time deltaT){

	m_sfFrameTime += deltaT;

	//If one second as passed then change frame
	if(m_sfFrameTime >= sf::seconds(1)){

		m_sfFrameTime = sf::seconds(0);
		if(m_iCurrentFrame == m_iXFrames) m_iCurrentFrame = 0;

		if(m_CurrentDirection == LEFT) *m_Iter = m_LeftFrames[m_iCurrentFrame];
		if(m_CurrentDirection == RIGHT) *m_Iter = m_RightFrames[m_iCurrentFrame];


Edited by Crusable

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I don't see anywhere in your code where you initialize m_Iter.

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You have an iterator. The iterator never is assigned anything (as SiCrane noticed). However, the iterator is dereferenced so what it is (not) pointing at can be assigned to.



int *myInt = NULL; //Doesn't point to anything.
*myInt = 5; //Crash!


For example, you have:


*m_Iter = m_LeftFrames[0];


This says, "take what m_Iter" is already pointing to, and assign the value of m_LeftFrames[0] to it". It's not saying, "make it point to m_LeftFrames[0]", which I think is what you are wanting. Since m_Iter isn't yet pointing to anything, it's similar (in concept) to dereferencing a null pointer.


A normal pointer will work just as fine, but if you want a iterator, you have to do it like this:


m_Iter = m_LeftFrames.begin(); //Gets an iterator to the first element.
m_Iter = (m_LeftFrames.begin() + index); //Gets an iterator to the nth element.


Note that we assigned to the iterator without dereferencing it. Dereferencing gets the object it is pointing to.

Warning: Your iterators will become invalid if the container is resized or elements inserted or erased.

Edited by Servant of the Lord

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