c++ - 您如何构造一个可能引发异常的对象？

Question

这将超出范围，因此我无法使用它。

try
{
    SomeClass someObject({});
}
catch (std::exception & e)
{

}

someObject(x); // someObject does not exist because it goes out of scope

Answer 1

这是 std::optional 的有用应用程序。

std::optional<SomeClass> maybe_someobject;

try {
     maybe_someobject.emplace( /* Constructor parameters go here */);
} catch (...  /* or something specific */)
{
     /* catch exceptions */
     return; // Do not pass "Go". Do not collect $200.
}

SomeClass &someobject=maybe_someobject.value();

// Use someobject normally, at this point. Existing code will have to look
// very hard to be able to tell the difference.

这增加了一些开销，但它是最小的，但是您保留了完整的类型和RAII安全性。