Swift - 使用 drawInRect 绘制文本 :withAttributes:

Question

我在使用 Xcode 6.1 GM 时遇到了奇怪的问题。

let text: NSString = "A"
let font = NSFont(name: "Helvetica Bold", size: 14.0)

let textRect: NSRect = NSMakeRect(5, 3, 125, 18)
let textStyle = NSMutableParagraphStyle.defaultParagraphStyle().mutableCopy() as NSMutableParagraphStyle
textStyle.alignment = NSTextAlignment.LeftTextAlignment
let textColor = NSColor(calibratedRed: 0.147, green: 0.222, blue: 0.162, alpha: 1.0)

let textFontAttributes = [
    NSFontAttributeName: font,
    NSForegroundColorAttributeName: textColor,
    NSParagraphStyleAttributeName: textStyle
]

text.drawInRect(NSOffsetRect(textRect, 0, 1), withAttributes: textFontAttributes)

错误在行 let texFontAttributes...

Cannot convert the expression's type 'Dictionary' to type 'DictionaryLiteralConvertible'

此代码在 Xcode 6.1 GM 之前一直有效。

当我尝试将 textFontAttributes 声明为 NSDictionary 错误消息更改为:

Cannot convert the expression's type 'NSDictionary' to type 'NSString!'

我不知道如何解决这个问题:(

Answer 1

问题是 font 是可选的，因为方便的构造函数现在返回可选值，所以 font 需要解包才能成为字典中的值:

if let actualFont = font {
    let textFontAttributes = [
        NSFontAttributeName: actualFont,
        NSForegroundColorAttributeName: textColor,
        NSParagraphStyleAttributeName: textStyle
    ]

    text.drawInRect(NSOffsetRect(textRect, 0, 1), withAttributes: textFontAttributes)
}