ProtocolSwift

    CustomDebugStringConvertible

    A type with a customized textual representation suitable for debugging purposes.

    protocol CustomDebugStringConvertible

    Overview

    Swift provides a default debugging textual representation for any type. That default representation is used by the String(reflecting:) initializer and the debugPrint(_:) function for types that don’t provide their own. To customize that representation, make your type conform to the CustomDebugStringConvertible protocol.

    Because the String(reflecting:) initializer works for instances of any type, returning an instance’s debugDescription if the value passed conforms to CustomDebugStringConvertible, accessing a type’s debugDescription property directly or using CustomDebugStringConvertible as a generic constraint is discouraged.

    Conforming to the CustomDebugStringConvertible Protocol

    Add CustomDebugStringConvertible conformance to your custom types by defining a debugDescription property.

    For example, this custom Point struct uses the default representation supplied by the standard library:

    struct Point {
        let x: Int, y: Int
    }
    
    let p = Point(x: 21, y: 30)
    print(String(reflecting: p))
    // Prints "Point(x: 21, y: 30)"

    After adding CustomDebugStringConvertible conformance by implementing the debugDescription property, Point provides its own custom debugging representation.

    extension Point: CustomDebugStringConvertible {
        var debugDescription: String {
            return "(\(x), \(y))"
        }
    }
    
    print(String(reflecting: p))
    // Prints "(21, 30)"

    Requirements

    Instance Properties