Swift中的base64EncodedStringWithOptions失败，出现编译错误 [英] base64EncodedStringWithOptions in Swift fails with compile error

问题描述

let dataStr = data.base64EncodedStringWithOptions(options: Encoding64CharacterLineLength)

不与使用未解析的标识符'Encoding64CharacterLineLength'一起编译" 当我只是使用

Doesn't compile with "Use of unresolved identifier 'Encoding64CharacterLineLength'" When I just change the param to zero with

let dataStr = data.base64EncodedStringWithOptions(options: 0)

它甚至给出了一个陌生的错误:无法转换类型为'String！的表达式！键入"String！".我找到了一种使用NSData初始化NSString的方法(但是，我仍然无法得到String和NSString之间的区别)，但我真的很好奇为什么这两行代码不起作用.

It gives even stranger error: "Cannot convert the expression of type 'String!' to type 'String!'" I found a way to init NSString with NSData (however, I still can't get the difference between String and NSString), but I'm really curious why these two lines of code don't work.

推荐答案

除非显式给出外部名称，否则Swift中方法的第一个参数不是命名参数.因此，您应该这样做:data.base64EncodedStringWithOptions(x)没有options:部分.

Unless explicitly given an external name, first argument of a method in Swift is not a named argument. Therefore you should be doing: data.base64EncodedStringWithOptions(x) without the options: part.

如果您实际查看参数类型NSDataBase64EncodingOptions，您会注意到它是一个符合RawOptionSet的结构，带有用于选项常量的静态变量.因此，要使用它们，您应该执行以下操作:NSDataBase64EncodingOptions.Encoding64CharacterLineLength

If you actually look at the argument type, NSDataBase64EncodingOptions, you'll notice that it is a struct conforming to RawOptionSet with static variables for option constants. Therefore to use them you should do: NSDataBase64EncodingOptions.Encoding64CharacterLineLength

NSDataBase64EncodingOptions结构(或通常为RawOptionSet)也不能从整数文字(如0)转换.但是它确实符合NilLiteralConvertible的要求，因此如果您不希望使用任何选项，则可以传递nil.

The NSDataBase64EncodingOptions struct (or RawOptionSet in general) is also not convertible from integer literals (like 0). But it does conform to NilLiteralConvertible so if you don't want any options you can pass nil.

放在一起:

let dataStr = data.base64EncodedStringWithOptions(NSDataBase64EncodingOptions.Encoding64CharacterLineLength)

或

let dataStr = data.base64EncodedStringWithOptions(nil)

Swift3.0

let dataStr = data.base64EncodedString(options: [])

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