let attrString = NSAttributedString (
            string: "title-title-title",
            attributes: [NSAttributedStringKey.foregroundColor: UIColor.black])

细节

Swift 5.2, Xcode 11.4 (11E146)

解决方案

protocol AttributedStringComponent {
    var text: String { get }
    func getAttributes() -> [NSAttributedString.Key: Any]?
}

// MARK: String extensions

extension String: AttributedStringComponent {
    var text: String { self }
    func getAttributes() -> [NSAttributedString.Key: Any]? { return nil }
}

extension String {
    func toAttributed(with attributes: [NSAttributedString.Key: Any]?) -> NSAttributedString {
        .init(string: self, attributes: attributes)
    }
}

// MARK: NSAttributedString extensions

extension NSAttributedString: AttributedStringComponent {
    var text: String { string }

    func getAttributes() -> [Key: Any]? {
        if string.isEmpty { return nil }
        var range = NSRange(location: 0, length: string.count)
        return attributes(at: 0, effectiveRange: &range)
    }
}

extension NSAttributedString {

    convenience init?(from attributedStringComponents: [AttributedStringComponent],
                      defaultAttributes: [NSAttributedString.Key: Any],
                      joinedSeparator: String = " ") {
        switch attributedStringComponents.count {
        case 0: return nil
        default:
            var joinedString = ""
            typealias SttributedStringComponentDescriptor = ([NSAttributedString.Key: Any], NSRange)
            let sttributedStringComponents = attributedStringComponents.enumerated().flatMap { (index, component) -> [SttributedStringComponentDescriptor] in
                var components = [SttributedStringComponentDescriptor]()
                if index != 0 {
                    components.append((defaultAttributes,
                                       NSRange(location: joinedString.count, length: joinedSeparator.count)))
                    joinedString += joinedSeparator
                }
                components.append((component.getAttributes() ?? defaultAttributes,
                                   NSRange(location: joinedString.count, length: component.text.count)))
                joinedString += component.text
                return components
            }

            let attributedString = NSMutableAttributedString(string: joinedString)
            sttributedStringComponents.forEach { attributedString.addAttributes($0, range: $1) }
            self.init(attributedString: attributedString)
        }
    }
}

使用

let defaultAttributes = [
    .font: UIFont.systemFont(ofSize: 16, weight: .regular),
    .foregroundColor: UIColor.blue
] as [NSAttributedString.Key : Any]

let marketingAttributes = [
    .font: UIFont.systemFont(ofSize: 20.0, weight: .bold),
    .foregroundColor: UIColor.black
] as [NSAttributedString.Key : Any]

let attributedStringComponents = [
    "pay for",
    NSAttributedString(string: "one",
                       attributes: marketingAttributes),
    "and get",
    "three!\n".toAttributed(with: marketingAttributes),
    "Only today!".toAttributed(with: [
        .font: UIFont.systemFont(ofSize: 16.0, weight: .bold),
        .foregroundColor: UIColor.red
    ])
] as [AttributedStringComponent]
let attributedText = NSAttributedString(from: attributedStringComponents, defaultAttributes: defaultAttributes)

完整的示例

不要忘记在这里粘贴解决方案代码

import UIKit

class ViewController: UIViewController {

    private weak var label: UILabel!
    override func viewDidLoad() {
        super.viewDidLoad()
        let label = UILabel(frame: .init(x: 40, y: 40, width: 300, height: 80))
        label.numberOfLines = 2
        view.addSubview(label)
        self.label = label

        let defaultAttributes = [
            .font: UIFont.systemFont(ofSize: 16, weight: .regular),
            .foregroundColor: UIColor.blue
        ] as [NSAttributedString.Key : Any]

        let marketingAttributes = [
            .font: UIFont.systemFont(ofSize: 20.0, weight: .bold),
            .foregroundColor: UIColor.black
        ] as [NSAttributedString.Key : Any]

        let attributedStringComponents = [
            "pay for",
            NSAttributedString(string: "one",
                               attributes: marketingAttributes),
            "and get",
            "three!\n".toAttributed(with: marketingAttributes),
            "Only today!".toAttributed(with: [
                .font: UIFont.systemFont(ofSize: 16.0, weight: .bold),
                .foregroundColor: UIColor.red
            ])
        ] as [AttributedStringComponent]
        label.attributedText = NSAttributedString(from: attributedStringComponents, defaultAttributes: defaultAttributes)
        label.textAlignment = .center
    }
}

结果

Swift: xcode 6.1

    let font:UIFont? = UIFont(name: "Arial", size: 12.0)

    let attrString = NSAttributedString(
        string: titleData,
        attributes: NSDictionary(
            object: font!,
            forKey: NSFontAttributeName))

Xcode 6版本:

let attriString = NSAttributedString(string:"attriString", attributes:
[NSForegroundColorAttributeName: UIColor.lightGrayColor(), 
            NSFontAttributeName: AttriFont])

Xcode 9.3版本:

let attriString = NSAttributedString(string:"attriString", attributes:
[NSAttributedStringKey.foregroundColor: UIColor.lightGray, 
            NSAttributedStringKey.font: AttriFont])

Xcode 10, iOS 12, Swift 4:

let attriString = NSAttributedString(string:"attriString", attributes:
[NSAttributedString.Key.foregroundColor: UIColor.lightGray, 
            NSAttributedString.Key.font: AttriFont])

斯威夫特3、4、5所示

使用下面的代码为文本颜色，字体，背景颜色和下划线/下划线颜色

    let text = "swift is language"
    let attributes = [NSAttributedString.Key.foregroundColor: UIColor.red, NSAttributedString.Key.backgroundColor: UIColor.blue,NSAttributedString.Key.font: UIFont.systemFont(ofSize: 25.0),NSAttributedString.Key.underlineColor: UIColor.white,NSAttributedString.Key.underlineStyle: NSUnderlineStyle.single.rawValue] as [NSAttributedString.Key : Any]
        
    let textAttribute = NSAttributedString(string: text, attributes: attributes)
    swiftLabel1.attributedText = textAttribute

使用这个示例代码。这是满足您需求的非常短的代码。这对我很有用。

let attributes = [NSAttributedStringKey.font : UIFont(name: CustomFont.NAME_REGULAR.rawValue, size: CustomFontSize.SURVEY_FORM_LABEL_SIZE.rawValue)!]

let attributedString : NSAttributedString = NSAttributedString(string: messageString, attributes: attributes)