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# Publishers.Merge4

A publisher created by applying the merge function to four upstream publishers.

```
struct Merge4<A, B, C, D> where A : Publisher, B : Publisher, C : Publisher, D : Publisher, A.Failure == B.Failure, A.Output == B.Output, B.Failure == C.Failure, B.Output == C.Output, C.Failure == D.Failure, C.Output == D.Output
```

## Topics

### Creating a merge-four publisher

[`init(_:_:_:_:)`](/documentation/Combine/Publishers/Merge4/init(_:_:_:_:))

Creates a publisher created by applying the merge function to four upstream publishers.

### Merging elements

[`merge(with:)`](/documentation/Combine/Publishers/Merge4/merge(with:))

[`merge(with:_:)`](/documentation/Combine/Publishers/Merge4/merge(with:_:))

[`merge(with:_:_:)`](/documentation/Combine/Publishers/Merge4/merge(with:_:_:))

[`merge(with:_:_:_:)`](/documentation/Combine/Publishers/Merge4/merge(with:_:_:_:))

### Declaring supporting types

[`Publishers.Merge4.Output`](/documentation/Combine/Publishers/Merge4/Output)

The kind of values published by this publisher.

[`Publishers.Merge4.Failure`](/documentation/Combine/Publishers/Merge4/Failure)

The kind of errors this publisher might publish.

### Inspecting publisher properties

[`a`](/documentation/Combine/Publishers/Merge4/a)

A publisher to merge.

[`b`](/documentation/Combine/Publishers/Merge4/b)

A second publisher to merge.

[`c`](/documentation/Combine/Publishers/Merge4/c)

A third publisher to merge.

[`d`](/documentation/Combine/Publishers/Merge4/d)

A fourth publisher to merge.

### Comparing publishers

[`==(_:_:)`](/documentation/Combine/Publishers/Merge4/==(_:_:))

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


---

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