Adding errors to inputs.

lib/simple_form/error.rb

@@ -0,0 +1,12 @@
+module SimpleForm
+  module Error
+
+    private
+
+      def generate_error
+        return '' unless errors = @object.errors[@attribute]
+        errors = errors.is_a?(Array) ? errors.to_sentence : errors
+        @template.content_tag(:span, errors, :class => 'error')
+      end
+  end
+end

lib/simple_form/form_builder.rb

@@ -1,12 +1,14 @@
 require 'simple_form/label'
 require 'simple_form/input'
 require 'simple_form/hint'
+require 'simple_form/error'
 
 module SimpleForm
   class FormBuilder < ActionView::Helpers::FormBuilder
     include SimpleForm::Label
     include SimpleForm::Input
     include SimpleForm::Hint
+    include SimpleForm::Error
 
     def input(attribute, options={})
       @attribute, @options = attribute, options
@@ -17,8 +19,9 @@ module SimpleForm
       label = generate_label
       input = generate_input
       hint  = generate_hint
+      error = generate_error
 
-      label << input << hint
+      label << input << hint << error
     end
 
     private

test/error_test.rb

@@ -0,0 +1,33 @@
+require 'test_helper'
+
+class ErrorTest < ActionView::TestCase
+
+  def setup
+    @super_user = SuperUser.new
+  end
+
+  test 'input should not generate error by default' do
+    simple_form_for @user do |f|
+      concat f.input :name
+    end
+    assert_no_select 'form span.error'
+  end
+
+  test 'input should generate error messages for attributes with a single error' do
+    simple_form_for @super_user do |f|
+      concat f.input :name
+      concat f.input :description
+    end
+    assert_select 'form span.error', "can't be blank"
+    assert_select 'form span.error', "must be longer than 15 characters"
+  end
+
+  test 'input should generate error messages for attributes with several errors' do
+    simple_form_for @super_user do |f|
+      concat f.input :age
+      concat f.input :credit_limit
+    end
+    assert_select 'form span.error', "is not a number and must be greater than 18"
+    assert_select 'form span.error', "must be present and must be greater than 0"
+  end
+end

test/support/models.rb

@@ -27,6 +27,10 @@ class User < OpenStruct
   def human_attribute_name(attribute)
     nil
   end
+
+  def errors
+    {}
+  end
 end
 
 class SuperUser < User
@@ -37,4 +41,13 @@ class SuperUser < User
       else super
     end
   end
+
+  def errors
+    @errors ||= {
+      :name => "can't be blank",
+      :description => "must be longer than 15 characters",
+      :age => ["is not a number", "must be greater than 18"],
+      :credit_limit => ["must be present", "must be greater than 0"]
+    }
+  end
 end