# ControlNotificationStream.contains(where:)

- **Module:** ControlNotificationStream
- **Package:** libtmux-swift
- **Language:** Swift
- **Kind:** method
- **Page:** https://libtmux.org/reference/swift/controlnotificationstream-contains(where-)/

```
ControlNotificationStream.contains(where:)(where: (Self.Element) async throws -> Bool) -> Bool
```

Returns a Boolean value that indicates whether the asynchronous sequence contains an element that satisfies the given predicate.

You can use the predicate to check for an element of a type that doesn’t
conform to the `Equatable` protocol, or to find an element that satisfies
a general condition.

In this example, an asynchronous sequence called `Counter` produces `Int`
values from `1` to `10`. The `contains(where:)` method checks to see
whether the sequence produces a value divisible by `3`:

    let containsDivisibleByThree = await Counter(howHigh: 10)
        .contains { $0 % 3 == 0 }
    print(containsDivisibleByThree)
    // Prints "true"

The predicate executes each time the asynchronous sequence produces an
element, until either the predicate finds a match or the sequence ends.

- Parameter predicate: A closure that takes an element of the asynchronous
  sequence as its argument and returns a Boolean value that indicates
  whether the passed element represents a match.
- Returns: `true` if the sequence contains an element that satisfies
  predicate; otherwise, `false`.

## Raises

- `Bool`