如何将多个枚举值作为函数参数传递

Question

我将如何执行以下操作 - 在swift中将两个NSStringDrawing选项作为函数参数传递:

CGRect boundingRect = [string boundingRectWithSize:CGSizeMake(280.0, NSIntegerMax)
                                                      options:NSStringDrawingUsesLineFragmentOrigin | NSStringDrawingUsesFontLeading
                                                   attributes:options context:nil];

Answer 1

编辑:在Swift 3.0中:

let options: NSStringDrawingOptions = [.usesLineFragmentOrigin, .usesFontLeading]

编辑:这是你如何使用Swift 2.0中的选项枚举:

let options: NSStringDrawingOptions = [.UsesLineFragmentOrigin, .UsesFontLeading]

编辑:此问题已在iOS 8.3 SDK Beta 1(12F5027d)中得到解决:

修改NSStringDrawingOptions[struct]

• 从: enum NSStringDrawingOptions : Int
• 至: struct NSStringDrawingOptions : RawOptionSetType

你现在可以写:

let options : NSStringDrawingOptions = .UsesLineFragmentOrigin | .UsesFontLeading

经过一些研究和@Anton Tcholakov的"评论":

1. 如果您的目标是OS X 10.10,这是一种简单的方法:

   let size = CGSize(width: 280, height: Int.max)
   let options : NSStringDrawingOptions = .UsesLineFragmentOrigin | .UsesFontLeading
   
   let boundingRect = string.bridgeToObjectiveC().boundingRectWithSize(size, options: options, attributes: attributes, context: nil)
   

2. 但是,在iOS 8 SDK中(在当前种子中),有一个错误,其中NSStringDrawingOptions移植到Swift enum : Int而不是struct : RawOptionSet.你应该向Apple发送一个错误报告来描述这个严重的问题.

Answer 2

更新了Xcode 6.3的答案:

在Xcode 6.3 Beta(Swift 1.2)中,这是最终修复的,你现在可以这样做:

let boundingRect = "string".boundingRectWithSize(size, options: .UsesLineFragmentOrigin | .UsesFontLeading, attributes:nil, context:nil)

对于旧版本:

它看起来像当前测试版中的一个错误,现在我编写Objective-C方法并使用Swift:

+ (NSStringDrawingOptions)combine:(NSStringDrawingOptions)option1 with:(NSStringDrawingOptions)option2
{
    return option1 | option2;
}

和调用形式Swift:

let boundingRect = "string".boundingRectWithSize(size, options: StringDrawingOptions.combine(.UsesLineFragmentOrigin, with: .UsesFontLeading), attributes:nil, context:nil)

Answer 3

另一种解决方案,使用unsafeBitCast.

如下所示:

let options = unsafeBitCast(NSStringDrawingOptions.UsesLineFragmentOrigin.rawValue | 
                            NSStringDrawingOptions.UsesFontLeading.rawValue,
                            NSStringDrawingOptions.self)