Extension - Model Tags

Simple examples

Query all records of a given model

<r:model name="Product">
  <r:find:each>
    <r:value name="id" />, 
    <r:value name="price" />, 
    <r:value name="name" /> <br>
  </r:find:each>
</r:model>

Simple search with conditions

<r:model name="Product">
  <r:find conditions="price>1">
    <r:each>
      <r:value name="id" />, 
      <r:value name="price" />, 
      <r:value name="name" /> <br>
    </r:each>
    Number of records returned: <r:count />
  </r:find>
</r:model>

Summary of the tags shown

model tag

Attribute:

• name: (required) specify model name here

model:find tag

There are two main operation modes for model:find:

• if id attribute was given that it returns the record with the given id
• if no id was specified than a group of records will be returned

Either modes support the same tags.

• limit, order, conditions attributes will be passed to Model.find(...)

If distinct attribute was given than the following query will run: SELECT DISTINCT(distinct) FROM model WHERE conditions etc…

Furthermore, there is a special page type called Filter that may give further filtering conditions. More on that later.

Functions that may be called on the returned data (or on the Model itself)

What described above is very basic, but real life may require more complex calculations. To support that model_tags gives you several possibilities:

• You may create class funcions (methods) that may be called using a special tag function
• You may create entity functions (methods) that may be called on the result records

This leads to potential secutity issues, that will be addressed in a very basic fashion. Now lets see this in action.

Class functions

First you need to prepare your model like this:

class Product < ActiveRecord::Base

  def self.myfunction(params=nil,conditions=nil)
    "returned value" 
  end

  def self.otherfunction(params=nil,conditions=nil)
    ["value1","value2"]
  end

  def self.thirdfunction(params=nil,conditions=nil)
    { 'key' => 'value', 'key2' => 'value2' } 
  end

  def self.fourthfunction(params=nil,conditions=nil)
    Product.find(...whatever...)
  end

  def self.function_is_allowed_to?(fun,user)
    ['myfunction','otherfunction','thirdfunction', 'fourthfunction'].include?(fun)
  end

end

• myfunction returns a string that maybe displayed this way

<r:model name="Product">
  <r:function name="myfunction">
    <r:each:value />
    <r:if_returned>Great! Returned a real value...</r:if_returned>
  </r:function>
</r:model>

• otherfunction returns an aray that may be displayed this way

<r:model name="Product">
  <r:function name="otherfunction">
    <r:each><r:value />, </r:each>
    Number of returned items: <r:count />
  </r:function>
</r:model>

please note the difference bw each:value and each,value

• thirdfunction returns a hash, that may be displayed this way:

<r:model name="Product">
  <r:function name="thirdfunction">
    <r:each:value name="key" />
    <r:each:value name="key2" />
  </r:function>
</r:model>

• fourthfunction returns an array of Products:

<r:model name="Product">
  <r:function name="fourthfunction">
    <r:each>
       <r:value name="id"/> <r:value name="price"/>, <br /> 
    </r:each>
    Number of returned products: <r:count />
  </r:function>
</r:model>

Instance functions

Instance functions may be created like class functions. They may return a single string, an array of values, a hash, an array of hashes or model instances. Same game. Prepare your model almost like above:

class Product < ActiveRecord::Base

  def myfunction(params=nil,conditions=nil)
    ["value1","value2"]
  end

  def function_is_allowed_to?(fun,user)
    ['myfunction'].include?(fun)
  end

end

• myfunction returns an aray that may be displayed this way

<r:model name="Product">
  <r:find>
    <r:each>
      <r:function name="otherfunction">
        <r:each><r:value />, </r:each>
        Number of returned items: <r:count />
      </r:function>
    </r:each>
  </r:find>
</r:model>

The important point here is that function tag is placed inside model:find:each instead of model. In the latter case the function is called on the Model class, in the former case on the returned Model instance. params=nil,conditions=nil parameters may be used to pass parameters and conditions to the function.

• params is an array that is the value of the attribute params split on commas like this: params=”1,2,3” => [“1”,”2”,”3”]
• conditions is the combined conditions given to the find tag and represented by the Filter url.