问题描述
我不知道如何使用AutoreleasingUnsafePointer.我有以下代码:
I don't know how to use the AutoreleasingUnsafePointer. I have the following code:
var myString: AutoreleasingUnsafePointer<NSString?>
myScanner.scanUpToCharactersFromSet(NSCharacterSet.newlineCharacterSet(), intoString: myString)
现在，我应该怎么做才能从"myString"中获取字符串?我知道它可以为nil，但是我想不出一种方法来获取字符串值，以防它不是nil.而且，Swift解包技术仅适用于Optional类型.
Now, what should I do to get the string from 'myString'? I know it can be nil, but I couldn't figure out a way to get the string value in case it wasn't nil. And the Swift unwrapping technique just only works with the Optional type.
谢谢！
推荐答案
如果将 scanUpToCharactersFromSet 的第二个参数声明为自动释放不安全指针，即 AutoreleasingUnsafePointer< NSString?> 您应该能够在不显式创建指针的情况下调用函数.Swift可让您在 NSString?变量上使用& 运算符来生成自动释放的不安全指针，如下所示:
If the second parameter of scanUpToCharactersFromSet is declared as autoreleasing unsafe pointer, i.e. AutoreleasingUnsafePointer<NSString?> you should be able to invoke your function without making a pointer explicitly. Swift lets you use & operator on an NSString? variable to produce an autoreleasing unsafe pointer, like this:
var str : NSString? = nil
myScanner.scanUpToCharactersFromSet(NSCharacterSet.newlineCharacterSet(), intoString:&str)
这将为您提供 str 作为正常"可选的 NSString ，您可以使用常规的解包运算符对其进行解包.
This would give you str as a "normal" optional NSString, which you can unwrap using the regular unwrapping operators.
这篇关于Swift:如何从AutoreleasingUnsafePointer< NSString"中获取值?从NSScanner?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！