gears::optparse::option Struct Reference

Represents a command line option. More...

Public Member Functions
	option (std::string name, std::string help="", value_type value=constant(true), trait flags=trait::none)
	Constructs an option from a long name, a description, a value, and trait.
	option (std::string name, char alias, std::string help="", value_type value=constant(true), trait flags=trait::none)
	Constructs an option from a long name, short name, a description, a value, and trait.
	option (char alias, std::string help="", value_type value=constant(true), trait flags=trait::none)
	Constructs an option from a short name, description, a value, and traits.
	option (const option &other)
	Copy constructor.
option &	operator= (const option &other)
	Copy assignment.
	option (option &&)=default
	Move constructor.
option &	operator= (option &&)=default
	Move assignment.
	~option ()=default
	Destructor.
bool	takes_value () const noexcept
	Checks if the option accepts a value.
size_t	nargs () const noexcept
	Returns the number of arguments expected by the value. More...
template<typename T >
const T &	get () const
	Retrieves the internal value of the option. More...
template<typename T >
const T &	get_or (const typename std::remove_reference< T >::type &def) const noexcept
	Retrieves the internal value of the option or a reasonable default. More...
bool	is_active () const noexcept
	Checks if the option has gone through parsing.
std::string	metavar () const noexcept
	Retrieves the internal option's metavar member. More...
bool	is (char arg) const noexcept
	Checks if the option is represented by a long or short option. More...
bool	is (const std::string &arg) const noexcept

Public Attributes
std::string	name
	The long name of the option, e.g. "help".
std::string	help
	The description used for the help output.
trait	flags
	The trait flags to modify the option's behaviour.
char	alias = '\0'
	The short name of the option, e.g. 'h'.

Related Functions
(Note that these are not member functions.)
enum	trait : char {   none = 0,   required = 1 << 0,   hidden = 1 << 1 }
	List of traits that modify an option's behaviour. More...

Detailed Description

A class that represents a command line option. A command line option is a command line argument used to specify information to the program.

Definition at line 53 of file option.hpp.

Member Function Documentation

template<typename T >

const T& gears::optparse::option::get ( ) const

inline

Retrieves the internal value of the option. If the option has no value then an exception is thrown.

Exceptions

std::runtime_error	Thrown if the option has not been parsed.
std::invalid_argument	Thrown for invalid casting or if the option has no value.

Returns

The internal value.

Definition at line 172 of file option.hpp.

template<typename T >

const T& gears::optparse::option::get_or ( const typename std::remove_reference< T >::type &  def ) const

inlinenoexcept

Retrieves the internal value of the option or a reasonable default. If the option has no value then the default is returned. If the type is not a valid cast then the default is returned.

Returns

The internal value or a reasonable default.

Definition at line 193 of file option.hpp.

bool gears::optparse::option::is ( char  arg ) const

inlinenoexcept

Checks if the option is represented by a long or short option. This function is typically used to avoid code repetition when handling predicates dealing with checking for a long name or short name. This is a member function rather than an operator== or operator!= to disallow obfuscation and code duplication (e.g. "help" == op vs op == "help").

Example usage:

optparse::option x = { "help", 'h', "show message" };
x.is("help");    // true
x.is('h');       // true
x.is("stuff");   // false

Parameters

arg	Long or short option to check for.

Returns

true if the option can be represented by arg.

Definition at line 153 of file option.hpp.

std::string gears::optparse::option::metavar ( ) const

inlinenoexcept

Retrieves the internal value's metavar member. If takes_value returns false, then an empty string is returned.

Returns

The internal value's metavar member.

Definition at line 215 of file option.hpp.

size_t gears::optparse::option::nargs ( ) const

inlinenoexcept

Returns

Returns the number of arguments expected by the value. If no value is expected, i.e. takes_value is false, then 0 is returned.

Definition at line 128 of file option.hpp.

Friends And Related Function Documentation

enum trait : char

related

List of traits that modify an option's behaviour. This allows you to set whether an option should be required or hidden. These are bit flags so they should be used similar to any other type of bit flag such as, e.g., std::ios_base.

Enumerator
none	Represents no traits being set.
required	The option is required to appear, or an error is thrown.
hidden	The option is suppressed from the default –help output.

Definition at line 40 of file option.hpp.