Data returned from another class is garbage

[leinad]

Hi,

I guess this a combination of a C++ and Qt question. More C++, but I'm using Qt as my framework.
I have an external class which has a bunch of methods. In one method it returns a pointer to a structure i.e. myStrcture *results.

In another class I'm calling the method from the other class to get results, but after I leave the method the results is garbage.

Example
myStructure * results = SecondClass::someMethod(arguments)
//if I look at results it's garbage

Second class:
mystructure *
SecondClass::someMethod(Arguments)
{
//do stuff here
return &results; //So far here is good (when I leave this method I get garbage)
}

I also tried this and doesn't help
SecondClass *test = new SecondClass;
myStructure * results = SecondClass->someMethod(arguments)
But still the same results. Any idea how I can get the correct results back. The SecondClass is not a QObject. Not sure if I need that but this I guess is basic C++ issue.

Thanks

[jsulm]

@leinad said in Data returned from another class is garbage:

return &results;

Where is "results" declared? Is it a local variable inside someMethod or is it class member?

[leinad]

The results is declared in the method of the second class.

[leinad]

As a local variable in that method. Should it be private so it doesn't go out of scope?

[jsulm]

@leinad said in Data returned from another class is garbage:

The results is declared in the method of the second class.

No wonder it is garbage then.

SecondClass::someMethod(Arguments)
{
    SomeStruct results; // results only exists as long as someMethod is being executed
                        // as soon as someMethod finishes results is destroyed
                        // so, you return a pointer to destroyed object
    return &results; //So far here is good (when I leave this method I get garbage)
}

You have two possibilities:

1. Allocate results on the heap (using new)
2. Make results class member

[leinad]

Great thanks.