Having a tough time understanding exception handling c++ [closed] - c++

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I am having a very tough time understanding exception handling after watching online tutorials and reading up on it. I am trying to pass test driven development, and I can't. What I have come up with so far is this. I am supposed to use this struct
struct ArrayException
{
ArrayException(string newMessage = "error") :message(newMessage)
{
}
string message;
};
The first try.
int sum(int* theArray, unsigned int arraySize)
{
try
{
if (theArray = NULL)
{
throw ArrayException("NULL ARRAY REFERENCE");
}
}
catch (int* param)
{
cout << "you can't have " << param << " as an array size";
}
int sum = 0;
for (int i = 1; i < arraySize; i++)
{
sum += theArray[i];
}
return sum;
}
I also tried doing it this way.
int sum(int* theArray, unsigned int arraySize)
{
if (theArray = NULL)
{
throw ArrayException("NULL ARRAY REFERENCE");
}
else
{
int sum = 0;
for (int i = 1; i < arraySize; i++)
{
sum += theArray[i];
}
return sum;
}
}

Answer 1

While the post does not specifically mention it, I take it that the question is why exception is not caught? The answer is simple - because exception thrown is of type ArrayException, and catch is done with the type int*.

Answer 2

The best way to get a grip on this stuff is as πάντα ῥεῖ recommended: get a good book. Here's a good place to start selecting books: The Definitive C++ Book Guide and List
The rest is a code block with comments where I figured they were needed.
#include <iostream>
// removed the using namespace std;
struct ArrayException
{
ArrayException(std::string newMessage = "error") :
message(newMessage)
{
}
std::string message;
};
int sum(int* theArray, size_t arraySize) // change made here:
// size_t better suited than unsigned int for indexes
{
//throw std::out_of_range("BOOM!"); //uncomment to trigger a std::exception
//throw 42; // uncomment to trigger the unknown exception
if (theArray == NULL)
{
throw ArrayException("NULL ARRAY REFERENCE"); //perfect!
}
else
{
int sum = 0;
for (size_t i = 0; i < arraySize; i++) // changes made here:
// size_t not int to get rid of signed/unsigned conflict
// starting with array index 0, not 1
{
sum += theArray[i];
}
return sum;
}
}
int main()
{
try
{
sum (NULL, 10); // NULL address to force the exception
}
catch (ArrayException & param) // catch the custom exception
// catch by reference where possible
{
std::cout << "This bad stuff happened: " << param.message << std::endl;
}
// extra stuff to show what can also be done
catch (std::exception & stdexcpt) // catch any standard exceptions and
// print their message
{
std::cout << "Standard exception thrown: " << stdexcpt.what() << std::endl;
}
catch (...) // catch anything else that was thrown and doesn't
// correspond to any expectation
{
std::cout << "No idea what happened." << std::endl;
}
}