Working with both strings and substrings

Question

Given that:

julia> SubString <: String
false

How would you write a function that accepts both substrings and strings?

julia> function myfunction(ss::String)
           @show ss, typeof(ss)
       end
myfunction (generic function with 1 method)

julia> myfunction("Hello World")
(ss, typeof(ss)) = ("Hello World", String)
("Hello World", String)

julia> s = split("Hello World")
2-element Array{SubString{String},1}:
 "Hello"
 "World"

julia> foreach(x -> myfunction(x), s)
ERROR: MethodError: no method matching myfunction(::SubString{String})
Closest candidates are:
  myfunction(::String) at REPL[11]:2

Answer 1

I think there are two ways you can do this:

1. Use AbstractString rather than String in the function definition;

2. Define the function twice, once for String and once for SubString, which will generate myfunction (generic function with 2 methods).

The point is that SubString is a subtype of AbstractString, not String. You can see this by entering supertype(SubString).