Returns an array containing the concatenated results of calling the given transformation with each element of this sequence.

SDK

- Xcode 10.2+

Framework

- Swift Standard Library

## Declaration

## Parameters

`transform`

A closure that accepts an element of this sequence as its argument and returns a sequence or collection.

## Return Value

The resulting flattened array.

## Discussion

Use this method to receive a single-level collection when your transformation produces a sequence or collection for each element.

In this example, note the difference in the result of using `map`

and `flat`

with a transformation that returns an array.

In fact, `s`

is equivalent to `Array(s`

.

Complexity: O(*m* + *n*), where *n* is the length of this sequence and *m* is the length of the result.