take strings for body

This makes the assignment for bodies easier when using plain Strings.
They get wrapped in an array as per rack definition.
For every other type, they have to implement each and get directly set
as body or have to be rendered to Strings first.

lib/zero/response.rb

@@ -4,7 +4,8 @@ module Zero
   #
   class Response
     attr_reader :status
-    attr_accessor :header, :body
+    attr_reader :body
+    attr_accessor :header
 
     # Constructor
     # Sets default status code to 200.
@@ -24,6 +25,23 @@ module Zero
       @status = status.to_i
     end
 
+    # set the body to a new value
+    #
+    # Use this function to set the body to a new value. It can either be an
+    # Object responding to `#each` per rack convention or a kind of string.
+    #
+    # @param content [#each, String] the content of the body
+    def body=(content)
+      content = [content] if content.kind_of?(String)
+
+      unless content.respond_to?(:each) then
+        raise ArgumentError.new(
+          "invalid body! Should be kind of String or respond to #each!")
+      end
+
+      @body = content
+    end
+
     # Returns the data of the response as an array:
     # [status, header, body]
     # to be usable by any webserver.

spec/unit/zero/response/body_spec.rb

@@ -9,4 +9,31 @@ describe Zero::Response do
       subject.body.should eq([])
     end
   end
+
+  describe '#body=' do
+    let(:string) { "new body" }
+    let(:array)  { ["new body"] }
+    let(:object_with_each) { {:a => "b" } }
+    let(:invalid_object)   { 12345 }
+
+    it "creates an array body for strings" do
+      subject.body = string
+      expect(subject.body).to eq(array)
+    end
+
+    it "sets the body to the array" do
+      subject.body = array
+      expect(subject.body).to be(array)
+    end
+
+    it "sets an object as string when responding to #each" do
+      subject.body = object_with_each
+      expect(subject.body).to be(object_with_each)
+    end
+
+    it "raises an argument error for invalid input" do
+      expect{subject.body = invalid_object}.to raise_error(
+                                                  ArgumentError, /invalid body/)
+    end
+  end
 end