allSatisfy(_:)

Publishes a single Boolean value that indicates whether all received elements pass a given predicate.

Declaration

func allSatisfy(_ predicate: @escaping (Self.Output) -> Bool) -> Publishers.AllSatisfy<Self>

Parameters

predicate:
A closure that evaluates each received element. Return true to continue, or false to cancel the upstream and complete.

Return Value

A publisher that publishes a Boolean value that indicates whether all received elements pass a given predicate.

Discussion

Use the allSatisfy(_:) operator to determine if all elements in a stream satisfy a criteria you provide. When this publisher receives an element, it runs the predicate against the element. If the predicate returns false, the publisher produces a false value and finishes. If the upstream publisher finishes normally, this publisher produces a true value and finishes.

In the example below, the allSatisfy(_:) operator tests if each an integer array publisher’s elements fall into the targetRange:

let targetRange = (-1...100)
let numbers = [-1, 0, 10, 5]
numbers.publisher
    .allSatisfy { targetRange.contains($0) }
    .sink { print("\($0)") }

// Prints: "true"

With operators similar to reduce(_:_:), this publisher produces at most one value.