Parsing to custom types

If you specify an arg_type setting (see the Argument entry settings section) for an option or an argument, parse_args will try to parse it, i.e. to convert the string to the specified type. This only works for a limited number of types, which can either be directly constructed from strings or be parsed via the Julia's built-in parse function. In order to extend this functionality to other types, including user-defined custom types, you need to overload the ArgParse.parse_item function. Example:

type CustomType
    val::Int
end

function ArgParse.parse_item(::Type{CustomType}, x::AbstractString)
    return CustomType(parse(Int, x))
end

Note that the second argument needs to be of type AbstractString to avoid ambiguity warnings. Also note that if your type is parametric (e.g. CustomType{T}), you need to overload the function like this: function ArgParse.parse_item{T}(::Type{CustomType{T}, x::AbstractString).