QScopeGuard Class

Provides a scope guard for calling a function at the end of a scope. More...

This class was introduced in Qt 5.12.

• List of all members, including inherited members

Public Functions

Related Non-Members

Detailed Description

QScopeGuard<F> is a class of which the sole purpose is to run the function f in its destructor. This is useful for guaranteeing your cleanup code is executed, whether the function is exited normally, exited early by a return statement, or exited by an exception.

Note: Exceptions are not supported. The callable shouldn't throw when executed, copied or moved.

See also QScopedValueRollback.

Member Function Documentation

Create a scope guard that will execute f at the end of the scope.

If F is a lambda, its type cannot be written. In that case you need to either rely on class template argument deduction (C++17 feature) and leave the template parameter out completely or use the helper function qScopeGuard() instead of this constructor.

This function was introduced in Qt 5.15.

void QScopeGuard::dismiss()

Disarms the scope guard, so that the function F will not be called at the end of the scope.

void myComplexCodeWithMultipleReturnPoints(int v)
{
    // The lambda will be executed right before your function returns
    auto cleanup = qScopeGuard([] { code you want executed goes HERE; });

    if (v == -1)
        return;

    int v2 = code_that_might_throw_exceptions();

    if (v2 == -1)
        return;

    (...)
}