Using New and Delete in inherited classes and stored pointers to the new object

ASnogarD · 2012-08-23T15:08:15

I am using much of the framework I got from http://www.sdltutorials.com/ , and while its entity class is great for creating new player entities I cant get the thing to make bullet entities... least not without generating exception faults. The way to make a player entity is straight forward, declare it in the source file , load its assets when entering the in game state and clear the assets when exiting ... no problem. The bullets however pose a number of issues, I cant declare each bullet beforehand.... they need to be created dynamically so I create one each time the player fires, and store it in the entity vector like the player... and when the bullet collides with a wall it dies, so I delete it and erase the element in the vector it was stored in. Code to create a bullet : Entity_Bullet* pBullet = new Entity_Bullet; pBullet->OnLoad(16,16,1,ENTITY_TYPE_BULLET_PLAYER); if(Facing == ENT_DIR_RIGHT) { pBullet->MoveRight = true; pBullet->MoveLeft = false; pBullet->X = X + Width; pBullet->Y = Y + (Height/2); } if(Facing == ENT_DIR_LEFT) { pBullet->MoveLeft = true; pBullet->MoveRight = false; pBullet->X = X - 20; pBullet->Y = Y + (Height/2); } Entity::EntityList.push_back(pBullet); The entity list is declared like this : std::vector<Entity*> Entity::EntityList; The code to remove the bullet is in the ingame state loop, where it goes through the entity vector and calls up each element. // Move , Animate and calculate actions for ALL entities for(unsigned int i = 0; i < Entity::EntityList.size(); i++) { if(!Entity::EntityList) continue; Entity::EntityList->OnLoop(); // If the entity is not a player if(Entity::EntityList->Type != ENTITY_TYPE_PLAYER) { // If the Entity is suppose to be destroyed if(Entity::EntityList->Dead == true) { Text::AddText("Dead one here", 10, 400); Entity::EntityList->OnCleanup(); if(Entity::EntityList->Type == ENTITY_TYPE_BULLET_PLAYER) { delete Entity::EntityList; } Entity::EntityList.erase(Entity::EntityList.begin() + (i --)); } } } The issue seems to be in the clearing up portion, I think there is a conflict in the vector when a few bullets are made and destroyed... I am thinking it is trying to store a bullet in a vector that was deleted but not cleared ? If I remove the delete and erase portions of the entity loop it runs without crashing, just leaves bullets all over the place. I would prefer the actual bullet class to delete the bullet during the OnCleanup() call, but using delete this crashes the game as soon as a bullet is fired, and I cant think of a way to identify the particular bullet beyond a this call. Hmm, would the bullet object go out of scope if the pointer ( or rather the element the pointer was erased ? ). Tips , ideas , advice welcome ... thanks. FYI - I havent just copied the tutorials code , I have modified a number of things in the code except for portions where I like how it works, ie I havent just copy pasted someone elses code and want you to sort out the bugs.

For Beginners

Started by ASnogarD August 21, 2012 01:06 PM

10 comments, last by ASnogarD 11 years, 8 months ago

DoctorGlow

1,813

August 23, 2012 02:05 PM

That may of been a cause for sure, however I deleted those classes to re-write them so I cant go check now.

Just FYI, it helps to use source control, even if you are the only one on the project, since then you will have all the history for all files and can go to any past version http://en.wikipedia....evision_control.

As far as which one to use, I think FAQ here might have more info.

ASnogarD

212

Author

August 23, 2012 03:08 PM

Well I am happy to report that the problem is sorted... as best as I can tell I am clearing every bullet and the element in the entity store that was holding the pointer to the bullet.
I have a static counter counting bullets as the constructor is called, and taking one off each time the destructor is called... and the numbers are consistant, I also check the number of elements in my vector ( basic int variable counts 1 each time an element is called , reports total count after loop, then resets ) and it show 1 for the player and the number of bullets consistantly.

.... plus the FPS dips when there is a LOT of bullets fired (over 98 in one trial, with keyboard repeat enabled ) but returns to the usual values when the bullets are cleared... I assume if there is a lot of bullets lost in the system it would degrade performance.

I basically got the same code in but the approach was different. I basically wrote the player and bullet as thier own classes without inheriting the entity class , then got both to behave properly as seperate classes... then I created the entity class and got the player and bullet classes to inherit from it and set everything to work via polymorphic inheritance.
In short I got the 2 classes to work properly before I made them into a fancy inherited polymorphic tree to eliminate inheritance issues and polymorphism bugs.

Finally... now I can add enemy entities, finish off the level editor ...and a ton of other shite... why do I do this again for ?

Using New and Delete in inherited classes and stored pointers to the new object

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