Add RDF.IRI.to_string/1

CHANGELOG.md

@@ -9,6 +9,8 @@ This project adheres to [Semantic Versioning](http://semver.org/) and
 
 ### Added
 
+- `RDF.IRI.to_string/1` returns the string representation of an `RDF.IRI`  
+  (implicitly resolving vocabulary namespace terms)
 - `RDF.Literal.matches?/3` for XQuery regex pattern matching
 - `RDF.Decimal.digit_count/1` and `RDF.Decimal.fraction_digit_count/1` for  
   determining the number of digits of decimal literals

lib/rdf/iri.ex

@@ -226,10 +226,30 @@ defmodule RDF.IRI do
     do: nil
 
 
-  defimpl String.Chars do
-    def to_string(%RDF.IRI{value: value}) do
-      value
-    end
-  end
+  @doc """
+  Returns the given IRI as a string.
 
+  Note that this function can also handle `RDF.Vocabulary.Namespace` terms.
+
+  ## Examples
+
+      iex> RDF.IRI.to_string RDF.IRI.new("http://example.com/#foo")
+      "http://example.com/#foo"
+      iex> RDF.IRI.to_string EX.foo
+      "http://example.com/#foo"
+      iex> RDF.IRI.to_string EX.Foo
+      "http://example.com/#Foo"
+
+  """
+  def to_string(iri)
+
+  def to_string(%RDF.IRI{value: value}),
+    do: value
+
+  def to_string(qname) when is_atom(qname),
+    do: qname |> new() |> __MODULE__.to_string()
+
+  defimpl String.Chars do
+    def to_string(iri), do: RDF.IRI.to_string(iri)
+  end
 end

test/unit/iri_test.exs

@@ -313,13 +313,26 @@ defmodule RDF.IRITest do
     end
   end
 
+  describe "to_string/1" do
+    test "with IRIs" do
+      assert IRI.to_string(IRI.new("http://example.com/")) == "http://example.com/"
+    end
 
-  test "to_string/1" do
+    test "with IRI resolvable namespace terms" do
+      assert IRI.to_string(EX.Foo) == "http://example.com/#Foo"
+      assert IRI.to_string(EX.foo) == "http://example.com/#foo"
+    end
+
+    test "with non-resolvable atoms" do
+      assert_raise RDF.Namespace.UndefinedTermError, fn -> IRI.to_string(Foo.Bar) end
+    end
+  end
+
+  test "String.Chars protocol implementation" do
     assert to_string(IRI.new("http://example.com/")) == "http://example.com/"
   end
 
-
-  test "inspect/1" do
+  test "Inspect protocol implementation" do
     assert inspect(IRI.new("http://example.com/")) == "~I<http://example.com/>"
   end