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# init(upstream:maxPublishers:transform:)

Creates a publisher that transforms elements from an upstream publisher into a new publisher.

```
init(upstream: Upstream, maxPublishers: Subscribers.Demand, transform: @escaping (Upstream.Output) -> NewPublisher)
```

## Parameters

`upstream`

The publisher from which this publisher receives elements.

`maxPublishers`

The maximum number of concurrent publisher subscriptions.

`transform`

A closure that takes an element as a parameter and returns a publisher that produces elements of that type.

---

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