ProtocolSwift5.9.0

CustomStringConvertible

A type with a customized textual representation.

protocol CustomStringConvertible

Types that conform to the CustomStringConvertible protocol can provide their own representation to be used when converting an instance to a string. The String(describing:) initializer is the preferred way to convert an instance of any type to a string. If the passed instance conforms to CustomStringConvertible, the String(describing:) initializer and the print(_:) function use the instance’s custom description property.

Accessing a type’s description property directly or using CustomStringConvertible as a generic constraint is discouraged.

Conforming to the CustomStringConvertible Protocol

Add CustomStringConvertible conformance to your custom types by defining a description 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(p)
// Prints "Point(x: 21, y: 30)"

After implementing the description property and declaring CustomStringConvertible conformance, the Point type provides its own custom representation.

extension Point: CustomStringConvertible {
    var description: String {
        return "(\(x), \(y))"
    }
}

print(p)
// Prints "(21, 30)"

Requirements

var description: String
A textual representation of this instance.

Citizens in Swift

Subtypes

protocol BinaryInteger
An integer type with a binary representation.
protocol CodingKey
A type that can be used as a key for encoding and decoding.
protocol FixedWidthInteger
An integer type that uses a fixed size for every instance.
protocol LosslessStringConvertible
A type that can be represented as a string in a lossless, unambiguous way.
protocol SIMD
A SIMD vector of a fixed number of elements.
protocol SignedInteger
An integer type that can represent both positive and negative values.
protocol StringProtocol
A type that can represent a string as a collection of characters.
protocol UnsignedInteger
An integer type that can represent only nonnegative values.

Available in _RegexParser

Members

var halfWidthCornerQuoted: String

Available in Foundation

Subtypes

protocol AttributedStringProtocol
protocol ReferenceConvertible
Decorates types which are backed by a Foundation reference type.

Extension in GRPC

Subtypes

protocol GRPCErrorProtocol
Requirements for GRPCError types.

Extension in Atomics

Subtypes

protocol AtomicInteger
A type that supports atomic integer operations through a separate atomic storage representation.

Extension in Crypto

Subtypes

protocol Digest
A type that represents the output of a hash.
protocol MessageAuthenticationCode
A type that represents a message authentication code.