Function template public_function

boost::contract::public_function — Program contracts for non-void public functions overrides (virtual or not).

Synopsis

// In header: <boost/contract/public_function.hpp>


template<typename Override, typename VirtualResult, typename F, 
         typename Class, typename... Args> 
  specify_precondition_old_postcondition_except< VirtualResult > 
  public_function(virtual_ * v, VirtualResult & r, F f, Class * obj, 
                  Args &... args);

Description

This is used to specify preconditions, postconditions, exception guarantees, old value copies at body, and check class invariants for public function overrides (virtual or not) that do not return void:

class u
    #define BASES private boost::contract::constructor_precondition<u>, \
            public b, private w
    : BASES
{
    friend class boost::contract::access;

    typedef BOOST_CONTRACT_BASE_TYPES(BASES) base_types;
    #undef BASES

    void invariant() const { // Optional (as for static and volatile).
        BOOST_CONTRACT_ASSERT(...);
        ...
    }

    BOOST_CONTRACT_OVERRIDES(f)

public:
    // Override from `b::f`.
    t f(t_1 a_1, ..., t_n a_n, boost::contract::virtual_* v = 0) {
        t result;
        boost::contract::old_ptr<old_type> old_var;
        boost::contract::check c = boost::contract::public_function<
                override_f>(v, result, &u::f, this, a_1, ..., a_n)
            .precondition([&] { // Optional.
                BOOST_CONTRACT_ASSERT(...);
                ...
            })
            .old([&] { // Optional.
                old_var = BOOST_CONTRACT_OLDOF(v, old_expr);
                ...
            })
            .postcondition([&] (t const& result) { // Optional.
                BOOST_CONTRACT_ASSERT(...);
                ...
            })
            .except([&] { // Optional.
                BOOST_CONTRACT_ASSERT(...);
                ...
            })
        ;

        ... // Function body (use `return result = return_expr`).
    }
    
    ...
};

A public function override should always call boost::contract::public_function otherwise this library will not be able to correctly use it for subcontracting.

See Also:

Public Function Overrides

Parameters:

`args`	All arguments passed to the enclosing public function override declaring the contract (by reference and in the order they appear in the enclosing function declaration), but excluding the trailing argument `v`.
`f`	A pointer to the enclosing public function override declaring the contract (but see Function Overloads).
`obj`	The object `this` from the scope of the enclosing public function override declaring the contract. This object might be mutable, `const`, `volatile`, or `const volatile` depending on the cv-qualifier of the enclosing function (volatile public functions will check volatile class invariants, see Volatile Public Functions).
`r`	A reference to the return value of the enclosing public function override declaring the contract. This is usually a local variable declared by the enclosing public function override just before the contract, but programmers must set it to the actual value being returned by the function at each `return` statement.
`v`	The trailing parameter of type `boost::contract::virtual_*` and default value `0` from the enclosing public function override.

Template Parameters:

`Args`	The types of all parameters passed to the enclosing public function override declaring the contract, but excluding the trailing parameter type `boost::contract::virtual_*`. On compilers that do not support variadic templates, this library internally implements this function using preprocessor meta-programming (in this case, the maximum number of supported arguments is defined by `BOOST_CONTRACT_MAX_ARGS`). (Usually these template parameters are automatically deduced by C++ and they do not need to be explicitly specified by programmers.)
`Class`	The type of the class containing the virtual public function declaring the contract. (Usually this template parameter is automatically deduced by C++ and it does not need to be explicitly specified by programmers.)
`F`	The function pointer type of the enclosing public function override declaring the contract. (Usually this template parameter is automatically deduced by C++ and it does not need to be explicitly specified by programmers.)
`Override`	The type trait `override_function-name` declared using the `BOOST_CONTRACT_OVERRIDE` or related macros. This template parameter must be explicitly specified (because there is no function argument from which it can be automatically deduced by C++).
`VirtualResult`	This type must be the same as, or compatible with, the return type of the enclosing public function override declaring the contract (this library might not be able to generate a compile-time error if these types mismatch, but in general that will cause run-time errors or undefined behaviour). Alternatively, `boost::optional<return-type>` can also be used (see Optional Return Values). (Usually this template parameter is automatically deduced by C++ and it does not need to be explicitly specified by programmers.)

Returns:

The result of this function must be assigned to a variable of type boost::contract::check declared explicitly (i.e., without using C++11 auto declarations) and locally just before the code of the public function body (otherwise this library will generate a run-time error, see BOOST_CONTRACT_ON_MISSING_CHECK_DECL).

Boost C++ Libraries