ControlNotificationStream.reduce(_:_:)

Description#

Use the reduce(_:_:) method to produce a single value from the elements of an entire sequence. For example, you can use this method on an sequence of numbers to find their sum or product.

The nextPartialResult closure executes sequentially with an accumulating value initialized to initialResult and each element of the sequence.

In this example, an asynchronous sequence called Counter produces Int values from 1 to 4. The reduce(_:_:) method sums the values received from the asynchronous sequence.

let sum = await Counter(howHigh: 4) .reduce(0) { $0 + $1 } print(sum) // Prints "10"

• Parameters:
  • initialResult: The value to use as the initial accumulating value. The nextPartialResult closure receives initialResult the first time the closure runs.
  • nextPartialResult: A closure that combines an accumulating value and an element of the asynchronous sequence into a new accumulating value, for use in the next call of the nextPartialResult closure or returned to the caller.
• Returns: The final accumulated value. If the sequence has no elements, the result is initialResult.