# Proxy

Proxy object provides access to a specific Primitive, Primitive data member, or nested data member within a Primitive for an element in a container.

## Description

accessor [index] or a Proxy object’s Data Member Interfaces return Proxy objects. That Proxy object represents the Primitive, Primitive data member, or nested data member within a Primitive for an element in a container. The Proxy object has the following features:

- A value_type can be exported or imported from the Proxy.

  - Conversion operator is used to export the value_type

  - Alternatively the Proxy can be passed to the function unproxy to export a value_type

  - Assignment operator = is used to import value_type into the Proxy

- Overloads the following operators if the underlying value_type supports the operator

  - ==, !=, <, >, <=, >=, +, -, *, /, %, &&, ||, &, |, ^, ~, *, +, -, !, +=, -=, *=, /=, %=, >>=, <<=, &=, |=, ^=, ++, --

  - When an operator is called the following occurs:

    - value_type is exported

    - The operator applied to the exported value

    - If the operator was an assignment, the result is imported back into the Member and returns the proxy

    - Otherwise a result is returned.

- Data Member Interface.

  - For each data member of value_type

    - A member access method is defined which returns a Member proxy representing just that member.

Member Type | Description
--- | ---
    typedef implementation-defined value_type
| The type of the data the Proxy is representing

Member | Description
--- | ---
    operator value_type const () const;
| Returns: exports a copy of the Proxy’s value. NOTE: constant return value prevents rvalue assignment for structs offering some protection against code that expected a modifiable reference.
    const value_type &
    operator = (const value_type &a_value);
| Imports a_value into container at the position the Proxy is representing. Returns: the same constant value_type it was passed. NOTE: This behavior is different from traditional assignment operators that return *this. Choice was to enable efficient chaining of assignment operators versus returning a Proxy which would have to export the value it had just imported.
    Proxy & operator = (const Proxy &other);
| Exports value from the other Proxy and imports it. Returns: A reference to this Proxy obect.
    auto name_of_values_data_member_1()const;
| Returns: Proxy instance representing the 1st data member of the value_type NOTE: actual method name is the name of the value_type’s 1st data member
    auto name_of_values_data_member_2()const;
| Returns: Proxy instance representing the 2nd data member of the value_type. NOTE: actual method name is the name of the value_type’s 2nd data member.
    auto name_of_values_data_member_...()const;
| Returns: Proxy instance representing the ...th data member of the value_type. NOTE: actual method name is the name of the value_type’s …th data member.
    auto name_of_values_data_member_N()const;
| Returns: Proxy instance representing the Nth data member of the value_type. NOTE: actual method name is the name of the value_type’s Nth data member

Parent topic: Proxy Objects