Expand scope of a variable initialized in a if/else sequence

Question

I\'m writing a piece of code in which I\'d like to use a different constructor of a class depending on a condition. So far I\'ve used if and else s

Answer 1

You can use a smart pointer instead of a direct instance:

std::unique_ptr my_object;

if (my_boolean) {
     //calling a first constructor
    my_object.reset(new MyClass(arg1));
}
else {
    //calling another constructor
    my_object.reset(new MyClass(arg1,arg2));
}
//more code using my_object

In contrast to some other solutions proposed here, this will also work for bigger if() {} else if() {} sequences, or switch blocks.

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In case you can't use a compiler capable of the latest standard, you can use the good old std::auto_ptr in the exactly same manner.

"I tried using the static keyword without success so far."

Good so! A static variable is certainly not what you want here.