For Loop

For Loop

Type: for-loop  ·  Package: Core Activities v1.0.8

Repeats a block of activities a counted number of times, keeping a numeric index that increases on each pass. Use it when you know how many times to repeat (go through 10 pages, generate 5 reports) and you are not looping through the elements of a collection.

How it works

Counts from from (included) up to to (excluded), adding step on each pass. On each iteration it stores the current value in the indexVariable variable and runs the activities.

from = 0, to = 3, step = 1   →   index takes 0, 1, 2   (3 passes; 3 does NOT run)
from = 1, to = 11, step = 1  →   index takes 1, 2, …, 10  (10 passes)
from = 0, to = 10, step = 2  →   index takes 0, 2, 4, 6, 8
from = 5, to = 5             →   0 passes (the flow continues without entering)

• from, to and step are rounded to integers before starting; the index is always an integer.
• The loop only counts up: it continues while the index is less than to. A step of 0 or a negative one with from < to never reaches the end and leaves the loop spinning; always use a positive step.
• It supports Break and Continue inside the body. Before each pass the loop checks whether the execution was terminated, so Terminate stops it between one pass and the next.

Required parameters

Parameter	Type	Default	Description
from	int	—	Start index (included). Rounded to an integer.
to	int	—	End index (excluded): the loop runs while the index is < to. Rounded to an integer.

Optional parameters

Parameter	Type	Default	Description
step	number	1	How much the index increases per pass. Must be greater than 0.
indexVariable	string	"i"	Name of the variable that holds the current index.

Sub-flows

activities required

Activities that run on each pass.

Output

This activity does not return a value. What it produces is the indexVariable variable, updated on each pass.

Example

Go through the first 5 pages of a web listing:

For Loop   from = 1   to = 6   indexVariable = page
 └─ activities:
      Page Navigate   url = "https://portal.example.com/list?page=" + page
      Log             level = info   message = "Processing page " + page

to is exclusive

To repeat N times starting at 1, use from = 1, to = N+1. To start at 0, use from = 0, to = N. If you expect 5 passes and only see 4, it is almost always because to (exclusive) is one short.

No need to declare the index

For Loop creates the indexVariable variable and updates it on each pass; you can use it in expressions ("page " + page). If you don’t name it, it is called i.

Common errors

Message	Cause and fix
'activities' is required.	The loop has no activities lane. Add at least one activity inside.
The loop never ends	step is 0 or negative, or the body never reaches an expected Break. Use a positive step.
One pass fewer than expected	to is exclusive. Add 1 to it.
The value of from, to or step cannot be converted to a number	The expression returned a text that is not a number. Convert it with num(...) or check the source variable.

Related activities

• For Each — when you loop through the elements of a list or table, not a count.
• While — when you don’t know how many passes, but depend on a condition.
• Break / Continue — exit the loop or skip to the next pass.