The default type is
None, which means the activity will not iterate.
Iterate
This type allows you to enter a number that represents the number of time you would like the activity to iterate without taking into account any condition for iterating.
Click
iterator to open the mapper to its right. You can either enter a number (integer) to specify the number of times the activity must iterate or you can set an expression for the loop by either entering the expression manually or mapping the output from the preceding activities or trigger. You can also use available functions along with the output from previous activities and/or manually entered values to form the loop expression. The loop expression determines the number of times the activity iterates.
Important: The loop expression must either return a number or an array. The array can be of any data type. If your loop expression returns a number, for example 3, your activity will iterate three times. If your loop expression returns an array, the activity will iterate as many times as the length of the array. You can hover over the expression after entering the expression to make sure that the expression is valid. If the expression is not valid, you will see a validation error pop up.
If you select this type, the
Input tab of the activity displays the
$iteration scope in the output area of the mapper.
$iteration contains three properties,
key,
index, and
value.
index is used to hold the index of the current iteration and
value holds the value that exists at the index location of the current iteration if the loop expression evaluates to an array. If the loop expression evaluates to an array of objects,
value also displays the schema of the object. If the loop expression evaluates to a number, the
value will contain the same integer as the
index for each iteration. To examine the result of each iteration of the activity, you can map
index and
value to the
message input property in the
LogMessage activity and print them.
key is used to hold the element name when configuring a condition if the value evaluates to an object. However, you can map only to the output of the last iteration if you did not set the
Accumulate Output checkbox to
Yes. See
Accumulating the Activity Output for All Iterations section for more details on this.
Repeat while true
Refer to
https://github.com/TIBCOSoftware/tci-flogo/tree/master/samples/app-dev/loops.sample for an example of how to use this feature.
Select this type if you want to set up a condition for the iteration. This acts like the
do-while loop where the first iteration is done without checking the condition and the subsequent iterations exit the loop or continue after checking the condition. You set the condition under which you want the activity to iterate by setting the
condition element. The condition gets evaluated before the next iteration of the activity. The activity iterates only if the condition evaluates to true. It stops iterating once the condition evaluates to false. Click
condition, and manually enter an expression for the condition. For example,
$iteration[index] > 5.
Keep in mind that even though the index for the
Repeat while true iteration begins at zero, it does not iterate n+1 times. If you enter 4 as the iterator value then it will execute as the following iterations: 0,1,2,3.
By default, the results of only the final iteration are saved and available. All previous iteration results are ignored. If you would like the results of all iterations to be stored and available, set
Accumulate to
Yes.
You have the option to set a time interval (in ms) between each iteration, which can help you manage the throughput for your machine. To spread the iterations out, set the
Delay element. Default delay time is 0 ms, which stands for no delay.
