AttributedString with String Interpolation

AttributedString.swift

//
//  AttributedString.swift
//
//  Created by fm.tonakai on 2019/04/08.
//

import UIKit

public struct AttributedString: ExpressibleByStringLiteral, ExpressibleByStringInterpolation, CustomStringConvertible {
    public struct StringInterpolation: StringInterpolationProtocol {
        public var attributedString: NSMutableAttributedString
        public init(literalCapacity: Int, interpolationCount: Int) {
            attributedString = NSMutableAttributedString()
        }

        public func appendLiteral(_ literal: String) {
            attributedString.append(NSAttributedString(string: literal))
        }

        public func appendInterpolation(_ linkText: String? = nil, URL url: URL) {
            let text = linkText ?? url.absoluteString
            attributedString.append(NSAttributedString(string: text, attributes: [.link: url]))
        }

        public func appendInterpolation(_ image: UIImage, bounds: CGRect? = nil) {
            let textAttachment = NSTextAttachment()
            textAttachment.image = image
            if let bounds = bounds {
                textAttachment.bounds = bounds
            }
            attributedString.append(NSAttributedString(attachment: textAttachment))
        }

        func appendInterpolation(_ text: String, attributes: [NSAttributedString.Key: Any]) {
            attributedString.append(NSAttributedString(string: text, attributes: attributes))
        }
    }
    public var attributedString: NSAttributedString
    public init(stringLiteral value: String) {
        attributedString = NSAttributedString(string: value)
    }

    public init(stringInterpolation: StringInterpolation) {
        attributedString = NSAttributedString(attributedString: stringInterpolation.attributedString)
    }

    public init(attributedString: NSAttributedString) {
        self.attributedString = attributedString
    }

    public var description: String {
        return attributedString.description
    }

}

public func + (lhs: AttributedString, rhs: AttributedString) -> AttributedString {
    let result = NSMutableAttributedString()
    result.append(lhs.attributedString)
    result.append(rhs.attributedString)
    return AttributedString(attributedString: NSAttributedString(attributedString: result))
}

public func += (lhs: inout AttributedString, rhs: AttributedString) {
    let result = NSMutableAttributedString()
    result.append(lhs.attributedString)
    result.append(rhs.attributedString)
    lhs.attributedString = NSAttributedString(attributedString: result)
}

AttributedStringPlayground.swift

import UIKit
import PlaygroundSupport

// add image named "image" in playground
var attrStr: AttributedString = "新規登録は\("こちら", URL: URL(string: "http://example.com/signin")!)\(UIImage(named: "image")!)\n"
attrStr = attrStr + "ログインは\("あちら", URL: URL(string: "http://example.com/login")!)"
print(attrStr)

let label = UILabel()
label.backgroundColor = .white
label.attributedText = attrStr.attributedString
label.numberOfLines = 0
label.sizeToFit()

PlaygroundPage.current.liveView = label