This class implements the following expressions : back, break, cancel, continue, jump, rewind, skip.

They are generally used inside of a ‘cursor’ (CursorExpression) or a ‘loop’ (LoopExpression), they can be used outside, but their result (the value of the field ‘__cursor_command__’ will be used as soon as the flow enters a cursor or a loop).

In fact, this expression is only a nice wrapper that sets the value of the field "__cursor_command__" to its name (‘back’ for example) plus to the ‘step’ attribute value.

For example <skip step="3"/> simply sets the value of the field ‘__cursor_command__’ to ‘skip 3’.

(The field __cursor_command__ is, by default, read and obeyed by the ‘cursor’ expression).

With Ruby process definitions, you can directly write :

    skip 2
    jump "0"

instead of

    skip :step => "2"
    jump :step => "0"

Likewise, in an XML process definition, you can write

    <skip>2</skip>

although that might still look lighter (it‘s longer though) :

    <skip step="2"/>

About the command themselves :

• back : will go back from the number of given steps, 1 by default
• break : will exit the cursor (or the loop)
• cancel : an alias for ‘break‘
• continue : will exit the cursor, if in a loop, will get back at step 0
• jump : will move the cursor (or loop) to an absolute given position (count starts at 0)
• rewind : an alias for continue
• skip : skips the given number of steps

All those command support an ‘if’ attribute to restrict their execution :

    cursor do
        go_to_shop
        check_prices
        _break :if => "${price} > ${f:current_cash}"
        buy_stuff
    end

The ‘rif’ attribute may be used instead of the ‘if’ attribute. Its value is some ruby code that, when evaluating to true will let the command be executed.

    _skip 2, :rif => "workitem.customers.size % 2 == 0"
        #
        # skips if the nb of customers is pair

Note that the ‘rif’ attribute will work only if the :ruby_eval_allowed parameter is set to true in the engine‘s application context.

    engine.application_context[:ruby_eval_allowed] = true