Swift-使用drawInRect：withAttributes绘制文本：

Question

我对Xcode 6.1 GM有一个奇怪的问题。

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)

错误处在让texFontAttributes …

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

直到Xcode 6.1 GM，此代码才能正常工作。

当我尝试将textFontAttributes声明为NSDictionary时，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

问题在于这font是可选的，因为便利构造函数现在返回可选值，因此font需要将其解包为字典中的值：

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

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