SubCommand

SubCommand type can be used to enumerate type for subcommands. This is a wrapper of SumType:

struct SubCommand(Commands...)

Public members

Copy constructor

Signature

this(T)(T value)

Parameters

T value
Value that is copied to a new object. Its type T must be one of the Commands.

Assignment operator

Signature

ref SubCommand opAssign(T)(T value)

Parameters

T value
Value to be assigned. Its type T must be one of the Commands.

isSetTo

Checks whether the object is set to a specific command type;

Signature

bool isSetTo(T)() const

Parameters

T
Type T must be one of the Commands.

Return value

true if object contains T type, false otherwise.

isSet

Checks whether the object is set to any command type;

Signature

bool isSet() const

Return value

If one of the Commands is a default command then this function always returns true.

In case if there is no default command, then:

true if object contains any type from Commands, false otherwise.

Default

Default type is a struct that can be used to mark a subcommand as default, i.e. it's chosen if no other subcommand is specified in command line explicitly.

This struct has no members and is erased by SubCommand before passing to internal SumType member.

Signature

struct Default(COMMAND)

matchCmd

matchCmd is a function template that is similar to std.sumtype.match but adapted to work with SubCommand.

Signature

template matchCmd(handlers...)
{
  auto ref matchCmd(Sub : const SubCommand!Args, Args...)(auto ref Sub sc)
  ...
}

Parameters

handlers
Functions that have the same meaning as for matchCmd function in standard library with an exception that they must not use Default type because the latter is erased by SubCommand (i.e. just use T instead of Default!T here).
sc
SubCommand parameter that the matching is applied to.

Return value

If sc is set to any subcommand (or has default one) then function returns the result from std.sumtype.match function.
Otherwise, init value of the type that would be returned from std.sumtype.match function if that type is not void.
Otherwise, this function has no return value (i.e. it's void).

Last modified: 24 October 2025