Contents

==(_:_:)

Returns a Boolean value indicating whether the left-hand-side argument is nil.

Declaration

static func == (lhs: borrowing Wrapped?, rhs: _OptionalNilComparisonType) -> Bool

Parameters

  • lhs:

    A value to compare to nil.

  • rhs:

    A nil literal.

Discussion

You can use this equal-to operator (==) to test whether an optional instance is nil even when the wrapped value’s type does not conform to the Equatable protocol.

The following example declares the stream variable as an optional instance of a hypothetical DataStream type. Although DataStream is not an Equatable type, this operator allows checking whether stream is nil.

var stream: DataStream? = nil
if stream == nil {
    print("No data stream is configured.")
}
// Prints "No data stream is configured."