How To Implement Nested Loops

 

Overview

Many surveys require the same question, or group of questions, to be repeated for multiple topics. For example, a respondent may first select the brands they are aware of, and then answer the same follow-up questions for each selected brand.

SurveyToGo supports this type of repeated flow through loop chapters, allowing you to reuse the same set of questions without duplicating them throughout the script.

In some cases, a survey may require more than one level of repetition. This is where nested loops are used.

Nested loops are loop chapters placed inside other loop chapters. Each loop runs within the context of the loop above it, allowing multiple levels of repeated logic and combined iteration values.

Basic Nested Loop Concepts

A nested loop, except for the outermost loop, is created as a sub-chapter of another loop chapter.

For example, if Loop 2 is placed inside Loop 1, then:

• Loop 1 is the parent loop.

• Loop 2 is the child loop.

• Loop 2 runs within each relevant iteration of Loop 1.

If another loop, Loop 3, is placed inside Loop 2, then:

• Loop 2 is the parent of Loop 3.

• Loop 1 is the grandparent of Loop 3.

Loop Level Indexes

Each loop in a nested loop structure has a level index. The level is counted from the current loop outward.

From the current loop's point of view:

• Level 0 refers to the current loop.

• Level 1 refers to the parent loop.

• Level 2 refers to the grandparent loop.

For example, if you are inside Loop 3:

• Loop 3 is level 0.

• Loop 2 is level 1.

• Loop 1 is level 2.

If you are inside Loop 2:

• Loop 2 is level 0.

• Loop 1 is level 1.

Iteration Context

Each loop has its own current iteration. During an interview, SurveyToGo may be in a specific combination of loop iterations.

For example, the current position may be:

2-3-1

This could mean:

• Outer loop: iteration 2

• First inner loop: iteration 3

• Second inner loop: iteration 1

When working with nested loops, it is important to reference the correct loop level and iteration.

Common Nested Loop Function

GetParentIterationIndex

Use GetParentIterationIndex(int level) to retrieve the current iteration index of a parent loop.

GetParentIterationIndex(level)

The level parameter indicates which parent loop to reference from the current loop's point of view.

Example

Suppose Loop A is the parent of Loop B, and you are currently inside a question in Loop B.

The current iteration state is:

• Loop A is on iteration 2.

• Loop B is on iteration 5.

You want to pipe the selected answer text from Q3, located in Loop A, into the current question in Loop B.

Because Loop A is level 1 from Loop B's point of view, use the following Start Script:

SetTextFormat(CurrQues, SelectedAnswerTextIter(Q3, GetParentIterationIndex(1)));

This script retrieves the current iteration index of Loop A and uses it to reference the correct iteration of Q3.

GetParentIterationName(int level): 

Gets a loop chapter’s level and returns its current iteration name (used exactly as is in GetParentIterationIndex()).

CreateMultiIterationsString(int[] iterations): 

Gets a list of iteration indexes from all relevant loop chapters, and creates a indexes string to later use to pull values entered in a specific iteration's state.

The list indexes order should be from the outermost loop to the innermost loop.

Example: In my survey I have 3 nested loops, “Loop C” that is nested in “Loop B” that is nested in “Loop A”. “Loop C” has a single choice question, Q10.

After completing the nested loops section, I want to pull the answer that was coded in Q10, while the iterations state was this: “Loop A” was in its fourth iteration, “Loop B” was in its second iteration, and “Loop C” was in its fourth iteration.

So, I’ll pull the value using this code:

AnswerIter(Q10, CreateMultiIterationsString(4, 2, 4));