From tnakajima at brain-tokyo.jp  Mon Jun 13 02:53:08 2005
From: tnakajima at brain-tokyo.jp (Taku Nakajima)
Date: Mon Jun 13 02:48:53 2005
Subject: [Amrita2-users] new ERB integration
Message-ID: <878y1epx2j.wl@brain-tokyo.jp>

Hi, amrita2-users!

I've got a new idea of integration ERB with Amrita2 and commited a
test code for it just now.

I think Amrita2 will be fit better with Rails and you can use helper
methods of Rails in Amrita2 template. I will complete the scaffold
generator using ths feature until next release.

This idea consists of some minor ideas. I will explain them step by
step. The samples are taken from test/test_erb.rb in the repository.
This dose not pass all the test codes now, but I will fix it soon.

== Binding as Presentation Object

Amrita2 will accept Binding Object now as well as Hash and Structs.

      t = TemplateText.new "<x id='a' />"
      a = 1
      t.expand(out="", binding) 
      assert_equal("<x>1</x>", out)

"binding" is a standard Ruby method which return a Binding Object.

If it was given for template expansion, Amrita2 will eval data for
it's sub elements like this.

      # b is a Binding Object given
      eval("a", b)

"a" will evaluated as a local variable name or a method name which can
be seen at the place where "binding" was called. In this case, there
is a local variable named as "a", so the value of it will be used.

== <span> with no attribute will be deleted

Now <span> tag with no attribute will be deleted at template expansion.

      t = TemplateText.new "<span><span id='a' /><span id='b' /></span>"
      a = 1
      b = 2
      t.expand(out="", binding) 
      assert_equal("12", out)

This add more compatiblity with Amrita1.0.

== CDATA section is evaluated as an ERB source

I added a new option 'eval_cdata_as_erb'. If this option was set, all
the <![CDATA[....]]> section of the template will be evaluated as ERB.

      t = TemplateText.new "<![CDATA[<%= 1+2 %>]]><span id='a' /><![CDATA[<%= 'xx'.upcase %>]]>"
      t.eval_cdata_as_erb = true
      t.expand(out="", :a=>1) 
      assert_equal("31XX", out)

== You can use one Binding for both old-Amrita2-style element and
   new-ERB-style element

    def em(s)
      %[<em>#{s}</em>]
    end

    def test_erb4
      t = TemplateText.new "<div><![CDATA[<%= em(a) %>]]><span id='b' /></div>"
      t.eval_cdata_as_erb = true
      a = 1
      b = 2
      t.expand(out="", binding) 
      assert_equal("<div><em>1</em>2</div>", out)
    end

In this case, "binding" was called in the test_erb3 where local
variable "a" and "b" and a method named "em" are available.

The variable "b" is used by "<span id='b' />"

The value of "b" is 2 so the result is "2"

The method "em" and te variable "a" is used in "<![CDATA[<%= em(a) %>]]>"

The value of "a" is 1 and the method "em" was called with it, so, the
result is "<em>1</em>".


== context-data

If CData section was in an element with id, you can use a variable
'$_' to which the data of PO will be assigned.

      t = TemplateText.new "<span id='a'><![CDATA[<%= $_ + b %>]]></span>"
      a = 1
      b = 2
      t.eval_cdata_as_erb = true
      t.expand(out="", binding) 
      assert_equal("3", out)


So you can use ERB in a Amrita-style loop.

      t = TemplateText.new "<ul><li id='list'><![CDATA[<%= ($_+1)*10 %>]]></li></ul>"
      list = 0..2
      t.eval_cdata_as_erb = true
      t.expand(out="", binding) 
      assert_equal("<ul><li>10</li><li>20</li><li>30</li></ul>", out)

== a more complex example

    def test_table
      t = TemplateText.new <<-END
      <table>
        <tr id='table_data'>
          <td id='aaa' />
          <td id='bbb'><![CDATA[<%= em($_)%>]]></td>
          <td id='ccc' />
          <td><![CDATA[<%= $_[:xxx] > 20 ? xxx + em($_[:xxx])  + $_[:aaa] : $_[:xxx] %>]]></td>
        </tr>
      <table>
      END
      xxx = 'xxx'
      table_data = [
        { :aaa=>'a1', :bbb=>'b1 ', :ccc=>'c1', :xxx=>10},
        { :aaa=>'a2', :bbb=>'b2 ', :ccc=>'c2', :xxx=>20},
        { :aaa=>'a3', :bbb=>'b3 ', :ccc=>'c3', :xxx=>30},
      ]
      t.eval_cdata_as_erb = true
      t.expand(out="", binding) 
      assert_equal_xml(<<-END, out)
      <table>
        <tr>
          <td>a1</td>
          <td><em>b1 </em></td>
          <td>c1</td>
          <td>10</td>
        </tr><tr>
          <td>a2</td>
          <td><em>b2 </em></td>
          <td>c2</td>
          <td>20</td>
        </tr><tr>
          <td>a3</td>
          <td><em>b3 </em></td>
          <td>c3</td>
          <td>xxx<em>30</em>a3</td>
        </tr>
      <table>
      </table>
      END
    end

The last column dose not have id, so the context-data($_) for it is a Hash

   template:
     <td><![CDATA[<%= $_[:xxx] > 20 ? xxx + em($_[:xxx])  + $_[:aaa] : $_[:xxx] %>]]></td>

   $_ is a Hash like
      { :aaa=>'a1', :bbb=>'b1 ', :ccc=>'c1', :xxx=>10},


   The result of this column is
     first:     <td>10</td>
     socond:    <td>20</td>
     third:     <td>xxx<em>30</em>a3</td>


--
Taku Nakajima