Question

What exactly is an “assert”, or more specifically, how do I get rid of an error. When I create a vector of pointers to a class with data member int x, and then do this:

for(I=antiviral_data.begin();I<antiviral_data.end();I++)
{
    if((*I)->x>maxx)
    {
        antiviral_data.erase(I);
    }
}

And run the program, I get no errors until x is greater than maxx and I use .erase(), at which point I get this error:

Debug Assertion Failed!

Program: …My Documents\O.exe File:
…include\vector Line: 116

Expression:
(“this->_Has_container()”,0)

For information on how your program
can cause an assertion failure, see
the Visual C++ documentation on
asserts.

(Press Retry to debug the application)

[Abort][Retry][Ignore]

Also, if I try to use cout:

cout<<(*antiviral_data.begin())->x<<endl;

I get this error:

Debug Assertion Failed!

Program: …My Documents\O.exe File:
…include\vector Line: 98

Expression: vector iterator not
deferencable

For information on how your program
can cause an assertion failure, see
the Visual C++ documentation on
asserts.

(Press Retry to debug the application)

[Abort][Retry][Ignore]

Could somebody please tell me why I can’t USE any of the data in the vector, and how to fix it?

ALSO: antiviral_data is a vector of pointers, with a single element:

antiviral_data.push_back(new aX1(player.x,player.y,'>'));

If that helps.

Answer 1

The most probable reason why you get the assertion is that you increment I after an erase. Try this instead:

for(I=antiviral_data.begin();I!=antiviral_data.end();)
{
    if((*I)->x>maxx) I=antiviral_data.erase(I); else ++I;
}

See also http://www.cppreference.com/wiki/stl/vector/erase , search for invalid iterators on that page.