NetNews Offline 2/NetNews Offline Volume 2.iso/news/comp/lang/c++-part1/3104

Text File | 1996-08-06 | 1.7 KB | 57 lines

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From: [e-mail] (Gary Edstrom)
Newsgroups: comp.lang.c++
Subject: Re: [Q] new-allocated objects within try block
Date: 20 Jan 1996 15:51:01 -0700
Organization: Sequoia Software
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Here is a way of handling your problem using an intermediate helper
class.  With this approach, you don't need to worry about executing
the new/delete operators.

class ABC { public: virtual void DoSomething() = 0; };
class A : public ABC { public: virtual void DoSomething(); };
class B : public ABC { public: virtual void DoSomething(); };

class Q
    {
    private:
        ABC * ptr;
    public:
        void DoSomething() { ptr->DoSomething(); }

        Q(test) { if (test) ptr = new A; else ptr = new B; }
        ~Q() { delete ptr; }
    };

Now, here is your modified try/catch block:

try {
    Q p(test);
    ...
    throw sthg;
    ...
    p.DoSomething();
    }
catch (...) { ... }

Using this approach, the destructor for Q will be executed
automatically after the program hits the "throw" statement.  Also
notice that the arrow notation has been changed to a dot notation.  To
as great a degree as possible, I try to follow the convention of only
using "new" operators inside constructors and "delete" operators
inside destructors.

Gary Edstrom <[e-mail]>

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