对于Swift 3和3.1，这工作得非常好:

passField.attributedPlaceholder = NSAttributedString(string: "password", attributes: [NSForegroundColorAttributeName: UIColor.white])

在我的例子中，我使用Swift 4

我为UITextField创建扩展

extension UITextField {
    func placeholderColor(color: UIColor) {
        let attributeString = [
            NSAttributedStringKey.foregroundColor: color.withAlphaComponent(0.6),
            NSAttributedStringKey.font: self.font!
            ] as [NSAttributedStringKey : Any]
        self.attributedPlaceholder = NSAttributedString(string: self.placeholder!, attributes: attributeString)
    }
}

yourField。placeholderColor(颜色:UIColor.white)

它更多的是个性化你的textField，但无论如何，我将分享这段代码从另一个页面，使它更好一点:

import UIKit
extension UITextField {
func setBottomLine(borderColor: UIColor, fontColor: UIColor, placeHolderColor:UIColor, placeHolder: String) {
    self.borderStyle = UITextBorderStyle.none
    self.backgroundColor = UIColor.clear
    let borderLine = UIView()
    let height = 1.0
    borderLine.frame = CGRect(x: 0, y: Double(self.frame.height) - height, width: Double(self.frame.width), height: height)
    self.textColor = fontColor
    borderLine.backgroundColor = borderColor
    self.addSubview(borderLine)
    self.attributedPlaceholder = NSAttributedString(
        string: placeHolder,
        attributes: [NSAttributedStringKey.foregroundColor: placeHolderColor]
    )
  }
}

你可以这样使用它:

self.textField.setBottomLine(borderColor: lineColor, fontColor: fontColor, placeHolderColor: placeHolderColor, placeHolder: placeHolder)

知道你有一个UITextField连接到一个ViewController。

来源:http://codepany.com/blog/swift-3-custom-uitextfield-with-single-line-input/

Swift 3(可能是2)，你可以覆盖didSet占位符在UITextField子类上应用属性，这样:

override var placeholder: String? {

    didSet {
        guard let tmpText = placeholder else {
            self.attributedPlaceholder = NSAttributedString(string: "")
            return
        }

        let textRange = NSMakeRange(0, tmpText.characters.count)
        let attributedText = NSMutableAttributedString(string: tmpText)
        attributedText.addAttribute(NSForegroundColorAttributeName , value:UIColor(white:147.0/255.0, alpha:1.0), range: textRange)

        self.attributedPlaceholder = attributedText
    }
}

添加带属性的占位符:

let attributes : [String : Any]  = [ NSForegroundColorAttributeName: UIColor.lightGray,
                                     NSFontAttributeName : UIFont(name: "Helvetica Neue Light Italic", size: 12.0)!
                                   ]
x_textfield.attributedPlaceholder = NSAttributedString(string: "Placeholder Text", attributes:attributes)

Swift 4

txtField1.attributedPlaceholder = NSAttributedString(string: "-", attributes: [NSAttributedStringKey.foregroundColor: UIColor.white])