== Why is this an issue?

A ``++std::optional<T>++`` can contain a value of type ``++T++``, or can be empty. So in order to avoid crashes or misbehaviors of code, it is better to check the presence of a value in an optional before accessing it. This can be done:

* By using the ``++has_value++`` member function
* By converting the optional to a boolean

Alternatively, the member function ``++value_or++`` can be used to return the contained value or a specific value if the optional is empty.


=== Noncompliant code example

[source,cpp]
----
using namespace std;

auto create(bool b) {
    return b ? optional<string>{"myString"} : nullopt;
}

void f(bool b) {
    auto str = create(b);
    cout << *str << endl; // Noncompliant, optional could be empty
}
----


=== Compliant solution

[source,cpp]
----
using namespace std;

auto create(bool b) {
    return b ? optional<string>{"myString"} : nullopt;
}

void f1(bool b) {
    auto str = create(b);
    if (str.hasValue()) {
        cout << *str << endl;
    }
}
void f2(bool b) {
    if (auto str = create(b)) {
        cout << *str << endl;
    }
}
void f3(bool b) {
    auto str = create(b);
    cout << str.value_or("<empty>") << endl;
}
----

ifdef::env-github,rspecator-view[]

'''
== Implementation Specification
(visible only on this page)

=== Message

Check this optional contains a value before accessing it.


endif::env-github,rspecator-view[]