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ara::core::Optional

It’s a wrapper for other types and a flag that indicates if the value is initialized or not.

struct ConfigurationParameters {
    std::string mandatoryParameter_1;  
    int32_t mandatoryParameter_2;  
    ara::core::Optional<std::string> optionalParameter_1;
    ara::core::Optional<int32_t> optionalParameter_2;
};

...

void processConfig(ConfigurationParameters& cfg) {
   // Process mandatory parameters as usual
   auto param1Value = cfg.mandatoryParameter_1;
   // use param1Value
   
   // for optional parameters first check their existence
   if(cfg.optionalParameter_1.has_value()) {
       // use optional parameter
       auto optionalParam = cfg.optionalParameter_1.value();
   }
}
  • Parameters
    • U the type of element in the container

class ara::core::Optional​

A container with at most one element The class template ara::core::Optional manages optional values, i.e. values that may or may not be present. The existence can be evaluated during both compile-time and runtime.

Members​

public inline constexpr Optional() noexcept​

Default constructor.

public inline constexpr Optional(nullopt_t) noexcept​

Construct empty optional from nullopt.

public constexpr Optional(Optional const & v) = default​

Copy construct from another Optional.

public constexpr Optional(Optional && v) = default​

Move value from another Optional.

public template<>
inline constexpr explicit Optional(in_place_t, Args &&... args) noexcept​

Internal In place constructor.

  • Parameters
    • Args arguments forwarded for inplace construction

public template<>
inline constexpr explicit Optional(in_place_t, std::initializer_list< T > il, Args &&... args) noexcept​

Internal In place constructor.

  • Parameters
    • T In place constructor type
    • Args arguments forwarded for inplace construction

public inline Optional(U const & v) noexcept​

Construct a new Optional object using provided value.

  • Parameters
    • v initial value

public inline Optional(U && v) noexcept​

Construct a new Optional object by moving the value.

  • Parameters
    • v initial value

public ~Optional() = default​

Destroy the Optional object.

public Optional&operator=(const Optional & rhs) = default​

Assignment operator. Please refer to C++17 documentation for more details.

  • Parameters

    • rhs source Optional object from where value is assigned

  • Returns Optional& reference to this object

public Optional&operator=(Optional && rhs) = default​

Assignment operator. Please refer to C++17 documentation for more details.

  • Parameters

    • rhs source Optional object from where value is assigned

  • Returns Optional& reference to this object

public inline Optional&operator=(nullopt_t) noexcept​

Remove any value contained in this Optional object. If no value is contained, then don't have any effect.

  • Returns Optional& reference to this object

public template<>
inline U & emplace(Args &&... args) noexcept​

Create the value in place and set it as the value for this Optional object. Please refer to C++17 documentation for more details.

  • Parameters

    • args arguments which are used to construct the value in place

  • Returns U& reference to the new value

public inline constexpr const U * operator->() const​

Return a pointer to the contained value Please refer to C++17 documentation for more details.

  • Returns constexpr const U* Pointer to the contained value

public inline constexpr U * operator->()​

Return a pointer to the contained value Please refer to C++17 documentation for more details.

  • Returns constexpr const U* Pointer to the contained value

public inline constexpr U & operator*()​

Return a reference to the contained value Please refer to C++17 documentation for more details.

  • Returns constexpr const U* Reference to the contained value

public inline constexpr const U & operator*() const​

Return a reference to the contained value Please refer to C++17 documentation for more details.

  • Returns constexpr const U* Reference to the contained value

public inline constexpr bool has_value() const noexcept​

Check whether the object contain any value.

  • Returns true if the object contain value

  • Returns false if the object doesn't contain value.

public inline constexpr explicit operator bool() const noexcept​

Check whether the object contain any value.

  • Returns true if the object contain value

  • Returns false if the object doesn't contain value.

public inline U & value()​

Return a reference to the value, if this Optional contain a value. Otherwise throw bad_optional_access exception.

  • Returns U&

public inline const U & value() const​

Return a reference to the value, if this Optional contain a value. Otherwise throw bad_optional_access exception.

  • Returns U&

public template<>
inline constexpr U value_or(T && t) const​

Return the value if this Optional contain a value, otherwise return the provided value of 't'.

  • Parameters

    • T type of t

  • Parameters

    • t default value to return if the Optional does not contain any value

  • Returns constexpr U

public template<>
inline constexpr U value_or(T && t)​

Return the value if this Optional contain a value, otherwise return the provided value of 't'.

  • Parameters

    • T type of t

  • Parameters

    • t default value to return if the Optional does not contain any value

  • Returns constexpr U

public inline void reset() noexcept​

Discard any value contained in this Optional object. Please refer to C++17 documentation for more details.

typedef value_type​

the type of element in the container