sizeWithAttributes 结果是"NSString is not identical to NSObject"

Question

我的代码在iOS 8.0上运行良好，由于我更新到了Xcode 6.1/SDK 8.1，我无法获得编译的swift代码

我正试图从类似的NSString中获取CGSize

let part1="my text"
let font = UIFont(name: "Arial", size: 30)
var dict = [NSFontAttributeName:font]
let size: CGSize = part1.sizeWithAttributes(dict)

在最后一行，我得到了错误"NSString与NSObject不相同"

有人能帮忙吗？

事实上，我找到了解决方案，下面是要添加的行，以使其发挥作用。

let part1="my text"
let font = UIFont(name: "Arial", size: 30)
if let fontNotNil=font {
    var dict = [NSFontAttributeName:fontNotNil]
    let size: CGSize = part1.sizeWithAttributes(dict)
}

Answer 1

尝试以下操作：

let part1: NSString = "my text"

Answer 2

选项都需要正确的展开"

let part1: NSString! = "my text"  // For the test since we do not know the type of part1
if let font = UIFont(name: "Arial", size: 30) {
    let dict = [NSFontAttributeName:font] as NSDictionary
    let size: CGSize = part1.sizeWithAttributes(dict)
    println("size: (size)")
}

输出：

尺寸：（96.6796875,33.515625）