---
title: upstream
framework: combine
role: symbol
role_heading: Instance Property
path: combine/publishers/buffer/upstream
---

# upstream

The publisher from which this publisher receives elements.

## Declaration

```swift
let upstream: Upstream
```

## See Also

### Inspecting publisher properties

- [size](combine/publishers/buffer/size.md)
- [prefetch](combine/publishers/buffer/prefetch.md)
- [whenFull](combine/publishers/buffer/whenfull.md)