In order to take advantage of the changes in Drupal 7, Views has gone through several API changes. Here's what you should know.

### Handler registry

Views now uses Drupal's dynamic-loading code registry. You can safely remove your implementations of hook_views_handlers(), since they are no longer used. Please remember to specify the handlers in your module's .info file. For example:

    name = Example module
    description = "Gives an example of a module."
    core = 7.x
    files[] = example.module
    files[] = example.install

    ; Views handlers
    files[] = includes/views/handlers/example_handler_argument_string.inc

### Removed handlers

Note that views_handler_filter_float has been removed. This functionality is now handled by views_handler_filter_numeric. There's no need for having a special handler any more, thanks to the new DB layer in Drupal 7. views_handler_sort_formula has been removed. Everyone who used it can extend from views_handler_sort, too.

### Ctools dependency

Views requires ctools now, so it can use the dependency system of ctools. The only thing you have to do is to replace

    '#process' => array('views_process_dependeny')

with

    '#process' => array('ctools_dependent_process'),

### Changed add_where api

If your field is a plain sql field: `$this->query->add_where($this->options['group'], "$this->table_alias.$this->real_field " . $this->operator . " '%s'", $this->value);` has to be converted to `$this->query->add_where($this->options['group'], "$this->table_alias.$this->real_field", $this->value, $this->operator);` If your field is a complex where condition: `$this->query->add_where($this->options['group'], "$upper($field) NOT LIKE $upper('%%%s')", $this->value);` has to be converted to `$placeholder = $this->placeholder(); $this->query->add_where_expression($this->options['group'], "$field LIKE $placeholder", array($placeholder => '%' . db_like($this->value)));` placeholder() generates a automatic unique placeholder for you. add_where with operator 'formula' can be converted to add_where_expression. add_having with operator 'formula' can be converted to add_having_expression.