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Amrita quick start guide

1. hello world

Amrita has two level APIs. This sample shows how to use Amrita's high level API: Amrita::TemplateFile and Amrita::TemplateText. They both are derived from Amrita::Template which wraps Amrita's low level API.

The sample codes in this document use only high level API.

HTML template

This is the simplest template for Amrita

<html>
  <body>
    <h1 id=title>title will be inserted here</h1>
    <p id=body>body text will be inserted here</p>
  </body>
</html>

Amrita treats an element with id attribute as a dynamic element and will get the data for it from model data by id attribute's value as key.

code

This is the code that use the template above and produce an output to STDOUT.

require "amrita/template"
include Amrita

tmpl = TemplateFile.new("template.html")
data = {
  :title => "hello world",
  :body => "Amrita is a html template libraly for Ruby"
}
tmpl.expand(STDOUT, data)

Amrita::Template mixes template with model data and produces output html document.

output

The output of this code is:

<html>
  <body>
    <h1>hello world</h1>
    <p>Amrita is a html template library for Ruby</p>
  </body>
</html>

The text "hello world" is picked up from model data by the key title and inserted into <h1> which has id="title" attribute. And <p id="body">...</p> was modified in the same way.

description

You can use Amrita in these steps.

1. Generate a Amrita::TemplateFile object with the path to template file.

tmpl = TemplateFile.new("template.html")

2. Make a model data for template expansion

data = {
  :title => "hello world",
  :body => "Amrita is a html template library for Ruby"
}

Model data can be various form but should be fit template's ID structure. In this case, template has two ids and they has value "title" and "body". So model data must provide data for "title" and "body".

3. call Amrita::Template#expand

tmpl.expand(STDOUT, data)

The first parameter of expand is the _stream_: amrita will put the output to it by << method. _stream_ can be IO including File, or String or Array or any objects that has << method.

2. list

This sample show how to make iteration with amrita. To copy a HTML element, mark it and give an Array to it.

code and output

code:

require "amrita/template"
include Amrita

tmpl = TemplateText.new <<END
<ul>
  <li id=list1>
</ul>
END
data = {
  :list1=>[ 1, 2, 3 ]
}
tmpl.prettyprint = true
tmpl.expand(STDOUT, data)

output:

<ul>
  <li>1</li>
  <li>2</li>
  <li>3</li>
</ul>

description

tmpl = TemplateText.new <<END
<ul>
  <li id=list1>
</ul>
END

This example uses Amrita::TemplateText class. This class accepts template as String instead of File, but can be used in same way to Amrita::TemplateFile.

data = {
  :list1=>[ 1, 2, 3 ]
}

Model data is a Hash who contains an Array as :list1's value. If model data of some HTML element is an Array (or an Enumerable object), amrita copies that element and expand each by each element of the Array.

tmpl.prettyprint = true
tmpl.expand(STDOUT, data)

If prettyprint is set to true, the output is pretty-printed.

3. table

code and output

code:

require "amrita/template"
include Amrita

tmpl = TemplateText.new <<END
<table border="1">
  <tr><th>name</th><th>author</th></tr>
  <tr id=table1>
    <td id="name"><td id="author">
  </tr>
</table>
END

data = {
  :table1=>[ 
    { :name=>"Ruby", :author=>"matz" },
    { :name=>"perl", :author=>"Larry Wall" },
    { :name=>"python", :author=>"Guido van Rossum" },
  ] 
}
tmpl.prettyprint = true
tmpl.expand(STDOUT, data)

output:

<table>
  <tr>
  <th>name</th>
  <th>author</th>
  </tr>
  <tr>
  <td>Ruby</td>
  <td>matz</td>
  </tr>
  <tr>
  <td>perl</td>
  <td>Larry Wall</td>
  </tr>
  <tr>
  <td>python</td>
  <td>Guido van Rossum</td>
  </tr>
</table>

description

<tr id="table1">...</tr> is copied three times because the model data for :table1 is an Array. And for each iteration, the child elements modified by the data {:name=>"...", :author=>"..." }

The model data can be complicated object like Array of Hash of Array of String....

Amrita applys each structure of model data to HTML template's ID structure recursively. So any HTML can be produced by amrita.

4. conditional

If model data of some element is nil or false, it will be deleted. Using this, you can select the part of template to be printed.

code and output

code:

require "amrita/template"
include Amrita

tmpl = TemplateText.new <<END
<html>
<body>
<div id="groups">
  <h1 id="title"></h1>
  <div id=no_data>
    <em>This group has no data.</em>
  </div>
  <div id=one_data>
    This group has only one data: "<span id=data></span>".
  </div>
  <div id=many_data>
    Here's the list of this group's data.
    <ul>
      <li id=list>
    </ul>
  </div>
</div>
</body>
</html>
END

data = [
  ["Group A", %w(only_one)],
  ["Group B", %w(one two three)],
  ["Group C", %w()]
]

model_data = data.collect do |name, d|
  hash = {:title => name }
  case d.size
  when 0
    hash[:no_data] = true
  when 1
    hash[:one_data] = { :data=>d[0] }
  else
    hash[:many_data] = { :list=>d }
  end
  hash
end

tmpl.prettyprint = true
tmpl.expand(STDOUT, { :groups=>model_data })

output:

<html>
  <body>
    <div>
      <h1>Group A</h1>
      <div> This group has only one data: "only_one".
      </div>
    </div>
    <div>
      <h1>Group B</h1>
      <div> Here's the list of this group's data.
        <ul>
          <li>one</li>
          <li>two</li>
          <li>three</li>
        </ul>
      </div>
    </div>
    <div>
      <h1>Group C</h1>
      <div>
        <em>This group has no data.</em>
      </div>
    </div>
  </body>
</html>

description

There are three <div id=...>...</div> parts in this template. Only one of those will be used. This sample sets only one key of no_data, one_data, many_data. Hash will be return nil for the key not set.So the part for nil is deleted.

If true was given as model data for some element, it will be printed unmodified.