std :: list :: erase（iter）异常处理C ++

Question

I try to get an iterator from a function and then erase an element from a list.

1. Is there any way to catch that exception?
2. Is there any way to know if the iterator is valid?

When I run the program with invalid iterator it throws the following exception:

 Exception thrown: read access violation.
 _Right.**_Myproxy** was 0xCCCCCCCC. occurred

My func is:

list<AccountStruct>::const_iterator SearchAccount(list<AccountStruct>& Acc,string p)
{

    for (list<AccountStruct>::const_iterator j = Acc.begin(); j !=Acc.end(); ++j)
    {
        if ((*j).phone == p) return j;
    }

}

void RemoveAccount(list<AccountStruct>& Acc)
{
    string Phone;
    cout << "Enter Phone Number ->" << endl;
    cin >> Phone;
    //cout << "Searching..." << endl;
    list<AccountStruct>::const_iterator iter = SearchAccount(Acc,Phone);
    try
    {
        Acc.erase(iter);
    }
    catch()// <- What to put inside??
    {
        cout << "No Phone Number;" << endl;
    }

}

Answer 1

We can fix this with a couple changes. First, SearchAccount doesn't return anything if the function does not find an object. This is undefined behavior, as you must return something when you say you will. We can fix this by returning end() if the item is not found like find does. That gives you

list<AccountStruct>::const_iterator SearchAccount(list<AccountStruct>& Acc,string p)
{
    for (list<AccountStruct>::const_iterator j = Acc.begin(); j !=Acc.end(); ++j)
    {
        if ((*j).phone == p) return j;
    }
    return Acc.end(); // item not found
}

Now that SearchAccount functions properly we can then check to see if end() is returned instead of using the exception mechanism. That look like

void RemoveAccount(list<AccountStruct>& Acc)
{
    string Phone;
    cout << "Enter Phone Number ->" << endl;
    cin >> Phone;
    //cout << "Searching..." << endl;
    list<AccountStruct>::const_iterator iter = SearchAccount(Acc,Phone);
    if (iter != Acc.end())
    {
        Acc.erase(iter);
    }
    else
    {
        cout << "No Phone Number;" << endl;
    }
}

And now you don't have the overhead of the exception mechanism and the "right thing" happens.

Answer 2

You should use ::std::remove_if algorithm

Acc.erase
(
    ::std::remove_if
    (
        Acc.begin()
    ,   Acc.end()
    ,   [&Phone](AccountStruct const & acc)
        {
            return(acc.phone == Phone);
        }
    )
,   Acc.end()
);

Answer 3

std::list::erase does not throw any exception.

The try block is not necessary. However an invalid iterator will cause undefined behavior.

You could return Acc.end() at after the for loop in SearchAccount and check the returned value against Acc.end instead of using try .