---
title: "initialize::sourceElementIndex"
framework: Compute Graph
role: symbol
role_heading: Function
platforms: [iOS 27.0+, iPadOS 27.0+, macOS 27.0+, tvOS 27.0+, visionOS 27.0+]
path: computegraph/initialize/sourceelementindex
---

# initialize::sourceElementIndex

When initializing a new particle from an event triggered from another particle, this returns the source particle’s index with its system.

## Declaration

```swift
uint initialize::sourceElementIndex()
```

## Discussion

Discussion note: