Class: Any
Any can contain any object by value. When an Any is constructed, the input value is copied or moved into the Any instance's private storage as well as a piece of unique type information.
The underlying type of an Any instance can be queried with the method is_a<T>(), which returns a boolean. The held value can be accessed with get<T>(), which returns a Maybe<T>. If the held value is not of type T, Nothing is returned.
The held value can also be accessed by reference by passing a closure to when<T>(...), where the closure will only be run if the type matches. The argument to the closure will be a reference to the held value.
The two related classes AnyRef and AnyConstRef behave identical to Any, except they don't own the value they refer to. Instead, they hold a reference and a const reference, respectively. Care must be taken to ensure that the lifetime of the AnyRef or AnyConstRef does not exceed the lifetime of the object they refer to (as a rule of thumb: use AnyRef/AnyConstRef in method signatures only, and never store the reference).
Constructors
Any(T&& value)
Construct an Any by moving value.
Any(const T& value)
Construct an Any by copying value.
Any(NothingType)
Construct an empty Any.
Any()
Identical to Any(NothingType).
Any(Any&&) and Any(const Any&)
Move or copy an Any, if the underlying type supports the respective operation.
If the underlying type does not support moving, the value will be copied instead. If the underlying type does not support copying, and a copy is requested, an exception is thrown.
Methods
is_a
Invoke: is_a<T>()
Returns: bool
Takes a template parameter T. Returns true if the held value has type T.
get
Invoke: get<T>()
Returns: Maybe<T>
Takes a template parameter T. Returns a Maybe<T> containing the value if the value has type T. Otherwise, returns Nothing.
when(closure)
Invoke: when<T>(closure)
Returns: Maybe<U>, where U is the return type of closure.
Takes a template parameter T and a generic closure/callback. If the held value is of type T, the closure is called with a reference to the held value.
Example:
Any any { (int)123 };
any.when<int>([](const int& number) {
std::cout << "Any was an int: " << number << std::endl;
});
type_info
Invoke: type_info()
Returns: A pointer to a TypeInfo.