---
title: "zip(_:_:_:_:)"
framework: combine
role: symbol
role_heading: Instance Method
path: "combine/publisher/zip(_:_:_:_:)"
---

# zip(_:_:_:_:)

Combines elements from three other publishers and delivers a transformed output.

## Declaration

```swift
func zip<P, Q, R, T>(_ publisher1: P, _ publisher2: Q, _ publisher3: R, _ transform: @escaping (Self.Output, P.Output, Q.Output, R.Output) -> T) -> Publishers.Map<Publishers.Zip4<Self, P, Q, R>, T> where P : Publisher, Q : Publisher, R : Publisher, Self.Failure == P.Failure, P.Failure == Q.Failure, Q.Failure == R.Failure
```

## Parameters

- `publisher1`: A second publisher.
- `publisher2`: A third publisher.
- `publisher3`: A fourth publisher.
- `transform`: A closure that receives the most-recent value from each publisher and returns a new value to publish.

## Return Value

Return Value A publisher that uses the transform closure to emit new elements, produced by combining the most recent value from four upstream publishers.

## Discussion

Discussion Use zip(_:_:_:_:) to return a new publisher that combines the elements from three other publishers using a transformation you specify to publish a new value to the downstream subscriber. The returned publisher waits until all four publishers have emitted an event, then delivers the oldest unconsumed event from each publisher together that the operator uses in the transformation. In this example, the PassthroughSubject publishers, numbersPub, fractionsPub, lettersPub, and emojiPub emit values. The zip(_:_:_:_:) operator receives the oldest value from each publisher and uses the Int from numbersPub and publishes a string that repeats the String from lettersPub and emojiPub that many times and prints out the value in fractionsPub. let numbersPub = PassthroughSubject<Int, Never>()      // first publisher let lettersPub = PassthroughSubject<String, Never>()   // second let emojiPub = PassthroughSubject<String, Never>()     // third let fractionsPub  = PassthroughSubject<Double, Never>()// fourth

cancellable = numbersPub     .zip(lettersPub, emojiPub, fractionsPub) { anInt, aLetter, anEmoji, aFraction  in         ("\(String(repeating: anEmoji, count: anInt)) \(String(repeating: aLetter, count: anInt)) \(aFraction)")     }     .sink { print("\($0)") }

numbersPub.send(1)         // numbersPub: 1       lettersPub:          emojiPub:          zip output: <none> numbersPub.send(2)         // numbersPub: 1,2     lettersPub:          emojiPub:          zip output: <none> numbersPub.send(3)         // numbersPub: 1,2,3   lettersPub:          emojiPub:          zip output: <none> fractionsPub.send(0.1)     // numbersPub: 1,2,3   lettersPub: "A"      emojiPub:          zip output: <none> lettersPub.send("A")       // numbersPub: 1,2,3   lettersPub: "A"      emojiPub:          zip output: <none> emojiPub.send("😀")        // numbersPub: 1,2,3   lettersPub: "A"      emojiPub:"😀"      zip output: "😀 A" lettersPub.send("B")       // numbersPub: 2,3     lettersPub: "B"      emojiPub:          zip output: <none> fractionsPub.send(0.8)     // numbersPub: 2,3     lettersPub: "A"      emojiPub:          zip output: <none> emojiPub.send("🥰")        // numbersPub: 3       lettersPub: "B"      emojiPub:          zip output: "🥰🥰 BB" // Prints: //1 😀 A 0.1 //2 🥰🥰 BB 0.8 If any upstream publisher finishes successfully or fails with an error, so too does the zipped publisher.

## See Also

### Collecting and republishing the oldest unconsumed elements from multiple publishers

- [zip(_:)](combine/publisher/zip(_:).md)
- [zip(_:_:)](combine/publisher/zip(_:_:)-4xn21.md)
- [zip(_:_:)](combine/publisher/zip(_:_:)-8d7k7.md)
- [zip(_:_:_:)](combine/publisher/zip(_:_:_:)-9yqi1.md)
- [zip(_:_:_:)](combine/publisher/zip(_:_:_:)-16rcy.md)