---
title: Future.Promise
framework: combine
role: symbol
role_heading: Type Alias
path: combine/future/promise
---

# Future.Promise

A type that represents a closure to invoke in the future, when an element or error is available.

## Declaration

```swift
typealias Promise = (Result<Output, Failure>) -> Void
```

## Mentioned in

Using Combine for Your App’s Asynchronous Code

## Discussion

Discussion The promise closure receives one parameter: a Result that contains either a single element published by a Future, or an error.

## See Also

### Creating a future

- [init(_:)](combine/future/init(_:).md)