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# Publishers.Zip3

A publisher created by applying the zip function to three upstream publishers.

```
struct Zip3<A, B, C> where A : Publisher, B : Publisher, C : Publisher, A.Failure == B.Failure, B.Failure == C.Failure
```

## Overview

Use a `Publishers.Zip3` to combine the latest elements from three publishers and emit a tuple to the downstream. The returned publisher waits until all three publishers have emitted an event, then delivers the oldest unconsumed event from each publisher as a tuple to the subscriber.

If any upstream publisher finishes successfully or fails with an error, so too does the zipped publisher.

## Topics

### Creating a zip-three Publisher

[`init(_:_:_:)`](/documentation/Combine/Publishers/Zip3/init(_:_:_:))

Creates a publisher that applies the zip function to three upstream publishers.

### Declaring supporting types

[`Publishers.Zip3.Output`](/documentation/Combine/Publishers/Zip3/Output)

The kind of values published by this publisher.

[`Publishers.Zip3.Failure`](/documentation/Combine/Publishers/Zip3/Failure)

The kind of errors this publisher might publish.

### Inspecting publisher properties

[`a`](/documentation/Combine/Publishers/Zip3/a)

A publisher to zip.

[`b`](/documentation/Combine/Publishers/Zip3/b)

A second publisher to zip.

[`c`](/documentation/Combine/Publishers/Zip3/c)

A third publisher to zip.

### Comparing publishers

[`==(_:_:)`](/documentation/Combine/Publishers/Zip3/==(_:_:))

Returns a Boolean value that indicates whether two publishers are equivalent.


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