------------------The Computed Field Drupal Module---------------------------- Computed Field is a cck module which lets you add a computed field to custom content types. You can choose whether to store your computed field in the database. You can also choose whether to display the field, and how to format it. The value of the field is set using php code, so it can draw on anything available to drupal, including other fields, the current user, database tables, etc. The drawback of this is of course that you need to know some php to use it. Computed Field requires the content module (cck). -------------------------Update------------------------------- As of 2006-8-11 the 'display format' setting has changed. You'll need to update any existing computed fields: If your display format was 'This is the value: %value', then change it to '$display = "This is the value: " . $node_field_item['value'];' -------------------------Usage-------------------------------- ----------Getting Started----------------------------------- Before you can use Computed Field, you'll need to get CCK and enable (at the very least) the 'content' module. You will probably also want to enable the other cck modules, such as 'text', 'number', 'date', etc. To add a computed field to a content type, go to administer > content > content types, select the content type you want to add to, and click on the 'add field' tab. One of the field types available should be 'Computed', and it should have one bullet point under it, also labelled 'Computed'. If you select this, give your field a name, and submit the form, you will get to the configuration page for your new computed field. --------Configuration--------------------------------------- A Computed Field can be configured with the usual cck field options, as well as the following extra options: Computed Code -- This is the code that will assign a value to your computed field. It should be valid php without the tags. Display Format -- This is also php code which should assign a string to the $display variable. It has '$node_field_item['value']' available, which is the value of the computed field. It also has '$field' available, and you can call any drupal functions you want to display your field. Store using the database settings below -- If this is checked then the field is computed on node save and stored. If it isn't stored then it will be recomputed every time you view a node containing this field. Database Storage Settings Data Type -- This is the sql data type to use to store the field. Let us know if you need any other storage types, or if you would like an 'other' option :). Data Length (varchar/text) -- The length of the field in the database. For storing usernames or other short text with a varchar field, 32 may be appropriate. Only valid for varchar or text fields. Data Size (int/float) -- The size of the field stored in the database. Only valid for int or float fields. Data Precision (decimal) -- The total number of digits to store in the database, including those to the right of the decimal. Only valid for decimal fields. Data Scale (decimal) -- The number of digits to the right of the decimal. Only valid for decimal fields. Default Value -- Leave this blank if you don't want the database to store a default value if your computed field's value isn't set. Not NULL -- Leave unchecked if you want to allow NULL values in the database field. Sortable -- Used in Views to allow sorting a column of this field. --------Examples------------------------------------------ Here are some usage examples to get you started with Computed Field. -----Make a node link to itself----------------- This example isn't very useful, but it demonstrates how to get hold of the nid. In your computed field's configuration: - Computed Code: // store the nid in our computed field $node_field[0]['value'] = $node->nid; - Check 'Display this field' - Display Format: $display = l('A link to this node', 'node/'.$node_field_item['value']); - Uncheck 'Store using the database settings below'. You could store this if you wanted to, but it's not costly to compute this field and is already stored in the node table. One reason why you may want to store it is if you want the value available to Views. When you display a node of the content type containing this field it should now have a link to itself. -----Adding two other fields---------------------- Imagine you have two existing number fields, called field_product_price and field_postage_price. You want to create a computed field field_total_cost which adds these two fields. Create a new computed field with the name 'Total Cost', and in your computed field's configuration set the following: - Computed Code: $node_field[0]['value'] = $node->field_product_price[0]['value'] + $node->field_postage_price[0]['value']; - Check 'Display this field' - Display Format: $display = '$' . $node_field_item['value']; - Check 'Store using the database settings below' - Data Type: decimal - Decimal Precision: 10 - Decimal Scale: 2 - Default Value: 0.00 - Check 'Not NULL' - Check 'Sortable' -----Calculating a Duration given a start and end time----- This example uses KarenS' date module (http://drupal.org/project/date) to create two date fields field_start_time and field_end_time which record hours and minutes. We then create a new computed field to work out the duration as a decimal number of hours (so 1.5 is 1hour, 30minutes). Computed field settings: - Computed Code: $start = $node->field_start_time[0]['value']; $end = $node->field_end_time[0]['value']; $start_decimal = $start['hours'] + ($start['minutes'] / 60); $end_decimal = $end['hours'] + ($end['minutes'] / 60); $node_field[0]['value'] = $end_decimal - $start_decimal; - Check 'Display this field' - Display Format: $display = $node_field_item['value'] . " hours"; - Check 'Store using the database settings below - Data Type: float - Data Size: normal - Check 'Sortable' Now if you set the start time field to 9am and the end time to 11:30am, your computed field will store the value '2.5' and display '2.5 hours'. -----Send more examples!--------------------------------- If you have another useful (or instructive) example send it to me (http://drupal.org/user/59132/contact) and I'll add it here for the benefit of humankind. -----------------------About Computed Field----------------------------------- Computed Field was created by Agileware (http://www.agileware.net).