meliorence/react-native-snap-carousel

Adjust index if data item is removed

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#157 opened on Sep 21, 2017

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 (17 comments) (6 reactions) (0 assignees)JavaScript (10,045 stars) (2,223 forks)batch import
*help wanted

Description

I want to use this component to let a user navigate through a (potentially endless) stream of items and as such I am adding new items to the data array as the user nears the end of the list and this works just perfectly. Obviously though I can't just keep adding items without removing older ones forever as this will exhaust memory at some point.

Removing items from the start of the data array seems to work pretty well except for the fact that it seems to act very strange with the index system. The problem is that the index doesn't change and after navigation there is a huge jump to the position of the old index+1. It would be nice if the component could automatically deal with this or provide me with a way to decrement the index without visually navigating.

Contributor guide

Tech stack
javascriptreact native
Domain
mobilefrontend
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
JavaScriptReact NativeState managementCarousel logic
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
40
Research direction
Examine the component's source code in index.js (or main file) to understand how the current index is managed and how data prop changes are handled. Look for existing logic that updates the index when data changes (e.g., componentDidUpdate or useEffect). The issue suggests that when items are removed from the start, the index should decrement accordingly. Investigate if there is an API to programmatically set the index without animation (e.g., snapToItem with animated false). Check if there are any closed PRs or issues that discuss similar index adjustments. Potential solution: In the data prop change handler, if the number of items decreased, adjust the current index by the difference if the removed items were before the current index. Ensure that the visual position is updated without animation.