this nullptr exception

[Andy90]

Hello, i have 2 components wich work together. So within 1 component i check some cases if they are true i call a function within a second component. When i call the function everything is fine but when i try to use this i get an nullptr exception. Here are my 2 codes

Component 1

else if (!pick.entity->tags.empty()) {
  for (auto tag : pick.entity->tags) {
    if (tag == "gather_water_task") {
      auto task = entity->GetComponent<GatherWaterTask>();
      task->OnTaskStart(entity, pick.entity, task);
      break;
    }
  } 
}

Component 2

void GatherWaterTask::OnTaskStart(shared_ptr<Entity> source, shared_ptr<Entity> dest, shared_ptr<GatherWaterTask> task) {
    Print("Task Started!");
    auto controler = source->GetComponent<MouseMovementController>();
    controler->destination = dest->GetPosition();
    this->taskStarted = true;
}

and the error

does anyone has an idee why this happens?

[Dreikblack]

11 minutes ago, Andy90 said:

this->taskStarted = true;

I'm not sure if there is a any difference but try GatherWaterTask::taskStarted = true;

 

[Andy90]

Same error. Well im kinda confused. Normaly it should work or ?

[Andy90]

Here is my class.

Header

#pragma once
#include "UltraEngine.h"
#include "MouseMovementController.h"

using namespace UltraEngine;

class GatherWaterTask : public Component
{
private:
    shared_ptr<Entity> entity;
    
public:
    string description;
    string title;
    long duration;
    long cooldown;
    bool taskStarted;

    GatherWaterTask();

    void OnTaskStart(shared_ptr<Entity> source, shared_ptr<Entity> dest, shared_ptr<GatherWaterTask> task);
    void OnTaskEnd();
    virtual void Start();
    virtual void Update();
    virtual bool Load(table& properties, shared_ptr<Stream> binstream, shared_ptr<Map> scene, const LoadFlags flags);
    virtual bool Save(table& properties, shared_ptr<Stream> binstream, shared_ptr<Map> scene, const SaveFlags flags);
    virtual shared_ptr<Component> Copy();
};

Source

#include "UltraEngine.h"
#include "GatherWaterTask.h"


using namespace UltraEngine;

GatherWaterTask::GatherWaterTask() {
	this->name = "GatherWaterTask"; // here this works
}

void GatherWaterTask::Start() {
    this->entity = GetEntity();
}

void GatherWaterTask::Update() {

}


void GatherWaterTask::OnTaskStart(shared_ptr<Entity> source, shared_ptr<Entity> dest, shared_ptr<GatherWaterTask> task) {
    Print("Task Started!");
    auto controler = source->GetComponent<MouseMovementController>();
    controler->destination = dest->GetPosition();
    this->taskStarted = true; // here this is null
}

void GatherWaterTask::OnTaskEnd() {

}

bool GatherWaterTask::Load(table& properties, shared_ptr<Stream> binstream, shared_ptr<Map> scene, const LoadFlags flags)
{
    this->title = properties["title"];
    this->description = properties["description"];
    return true;
}

bool GatherWaterTask::Save(table& properties, shared_ptr<Stream> binstream, shared_ptr<Map> scene, const SaveFlags flags)
{
    properties["title"] = this->title;
    properties["description"] = this->description;
    return true;
}

shared_ptr<Component> GatherWaterTask::Copy()
{
    return std::make_shared<GatherWaterTask>(*this);
}

 

[Dreikblack]

18 minutes ago, Andy90 said:

Same error. Well im kinda confused. Normaly it should work or ?

I'm just use class name instead of this to assign a value like this:

    void setTileMap(map<iVec3, shared_ptr<Tile>> tileMap)
    {
        Unit::tileMap = tileMap;
    }

But in your case you don''t need neither. I don't see a reason why you have a null pointer issue here but when you have no overlapping vars with same name you can just do:

 

taskStarted = true; 

 

btw all my components atm are hpp. I will rework them into .h and .cpp later but maybe that a reason? In beta with precompiler for a components .hpp was the only option.

 

 

[Andy90]

8 minutes ago, Dreikblack said:

taskStarted = true; 

 

i allready tryed this as well. Same problemm

[Andy90]

More wired things happend. I changed the header to an hpp and removed the c++ source file. After this its not possible anymore to access the other component. The compiler says that "MouseMovementController" is not declarated but i includet the header file for this....

 

#pragma once
#pragma once
#include "UltraEngine.h"
#include "MouseMovementController.hpp"

using namespace UltraEngine;

class CollectWaterTask : public Component
{
public:
    shared_ptr<Entity> entity;
    shared_ptr<Entity> player;
    shared_ptr<Map> scene;

    string description;
    string title;
    long duration;
    long cooldown;
    bool taskStarted;

    CollectWaterTask() {
        this->name = "CollectWaterTask";
    }

    virtual void Start() {
        this->entity = GetEntity();

        for (auto e : this->scene->entities) {
            auto controller = e->GetComponent<MouseMovementController>();
            if (controller != NULL)
            {
                this->player = e;
                break;
            }
        }
    }

    virtual void Update() {

    }

    virtual void OnTaskStart(shared_ptr<Entity> source, shared_ptr<Entity> dest, shared_ptr<CollectWaterTask> task) {
        auto controler = source->GetComponent<MouseMovementController>();
        controler->destination = dest->GetPosition();
        this->taskStarted = true; // here this is null
    }

    virtual void OnTaskEnd() {

    }

    virtual bool Load(table& properties, shared_ptr<Stream> binstream, shared_ptr<Map> scene, const LoadFlags flags)
    {
        this->scene = scene;
        this->title = properties["title"];
        this->description = properties["description"];
        return true;
    }

    virtual bool Save(table& properties, shared_ptr<Stream> binstream, shared_ptr<Map> scene, const SaveFlags flags)
    {
        properties["title"] = this->title;
        properties["description"] = this->description;
        return true;
    }

    virtual shared_ptr<Component> Copy()
    {
        return std::make_shared<CollectWaterTask>(*this);
    }
};

 

[Dreikblack]

Try to remove this include and add:

class MouseMovementController;

above class CollectWaterTask : public Component

 

 

[Andy90]

Ok the last error i managed to fix with geting back to header and source files. Back to the problem with the nullptr

[Josh]

Please upload your project so other people can run it. If "this" is NULL inside a method it means a method is being called on an object that does not exist. I'm not sure how that would be possible, but there is definitely something weird going on in the code.

[Andy90]

Ok its uploaded. You can find it here: https://1drv.ms/u/s!Aum5gwXzTrOyvzFp9Q_eF9_0AiZl?e=77digt

-----

You need to run the solution and then when the game is loaded left klick on the water well.

[Josh]

In MouseMovementController.cpp, GetComponent is returning null:

                else if (!pick.entity->tags.empty()) {
                    for (auto tag : pick.entity->tags) {
                        if (tag == "gather_water_task") {
                            auto task = entity->GetComponent<GatherWaterTask>();
                            task->OnTaskStart(entity, pick.entity);// set a breakpoint here and look at the task variable
                            break;
                        }
                    }
                }

 

[Andy90]

Omg you are right...it has to be the entity from the pick not the entity from the Mouse Controller  thanks alot. 

----

but if you have the project all ready you could have a look to the navmesh. The offset from the player character and the building from a bigger navmesh.