Course 16 Loop Expression скачать в хорошем качестве

Course 16 Loop Expression

A loop expression processes a set of rules on a given context for a number of times. The number of repetitions for executing the rules is defined by a numeric constant, a condition, or by iterating over the rows of a table. The expression can also contain exit conditions as well as continue conditions for the rules. The loop expression can either return a result that can be used for further processing or trigger actions. Features Processing Mode A loop expression can be executed in either of the following processing modes: Perform Action In this processing mode, the system automatically assigns the predefined Actions table object as result data object. After loop processing has finished, this table returns the list of all actions that have been triggered by the loop expression. Return Value In this processing mode, you can assign any kind of data objects as the expression's result data object. If you use this setting, it is up to you to make sure that the rules processed at runtime make changes to the value of the selected data object. Loop Mode You can choose between the following loop modes to further specify how exactly the loop expression shall operate: Repeat ... Times For this mode, you must specify a number indicating the number of iterations that the loop shall run through. You choose this loop mode for use cases where you know in advance the exact number of iterations needed. The only way for a so-defined loop expression to run through less iterations than defined is that an optional exit condition is fulfilled. Do ... Until ... For this mode, you have to define a cancellation criterion that must be fulfilled to make the loop expression stop processing. The cancellation criterion is tested after each iteration. This means that in a Do ... Until ... loop, the rules that have been defined for the expression are processed at least once. While ... Do ... For this mode, you have to define a continue criterion that must be fulfilled for the loop expression to continue processing. The continue criterion is tested before each iteration. This means that in a While ... Do ... loop, the rules that have been defined for the expression may not be processed at all. For Each Entry In ... In this mode, the number of iterations depends on the number of entries in a table that shall be used as the loop iteration controller. The object that you select as a controller must be either a table data object or an expression that has a table data object assigned as its result data object. This is the case, for example, for several of the table operation subtypes, or for a decision table or search tree expression in multiple match mode. The number of iterations can be further restricted by additional selection criteria that you may define for the table. The iteration controller object can be freely selected from all suitable objects in the system. It is not necessary to include that object in the expression context.