创建新的CharacterSet时执行EXC不良访问

问题描述

我正在尝试编写一个功能强大的函数，其中涉及去除连字符以外的所有标点符号.我认为最好的方法是创建一个新的CharacterSet，如下所示:

I'm trying to write a slugging function which involves stripping out any punctuation characters except for hyphens. I thought the best way to do this would be to create a new CharacterSet as follows:

import Foundation

extension CharacterSet {

    func subtracting(charactersIn string: String) -> CharacterSet {
        let unwantedCharacters = CharacterSet(charactersIn: string)
        return self.subtracting(unwantedCharacters)
    }


}

let punctuationCharactersExcludingHyphen = CharacterSet.punctuationCharacters.subtracting(charactersIn: "-")

<#slug function using punctuationCharactersExcludingHyphen#>

其中slug function是我已经使用现有字符集测试过的功能.问题是赋值let punctuationCharactersExcludingHyphen...与EXC_BAD_ACCESS code=2崩溃.

where slug function is a function that I've already tested with existing character sets. The problem is that the assignment let punctuationCharactersExcludingHyphen... crashes with a EXC_BAD_ACCESS code=2.

我已经注意到，涉及此错误的大多数问题是由某些特定的语法错误等引起的，但是我无法找到问题所在.有什么想法吗?

I've noticed that most problems involving this error are caused by some specific syntax error or the like, but I can't find out what it is here. Any ideas?

推荐答案

对我来说，这似乎是个错误.建立两个 any 的区别CharacterSet导致无限"递归和堆栈溢出.这是导致崩溃的最小示例:

That looks like a bug to me. Building the difference of any twoCharacterSets results in an "infinite" recursion and a stack overflow.Here is a minimal example which causes the crash:

let cs1 = CharacterSet.punctuationCharacters
let cs2 = CharacterSet.decimalDigits
let cs = cs1.subtracting(cs2)

一种解决方法是使用

public mutating func remove(charactersIn string: String)

CharacterSet的方法:

var punctuationCharactersExcludingHyphen = CharacterSet.punctuationCharacters
punctuationCharactersExcludingHyphen.remove(charactersIn: "-")

，或者如果您需要扩展方法:

or if you want an extension method:

extension CharacterSet {
    func subtracting(charactersIn string: String) -> CharacterSet {
        var cs = self
        cs.remove(charactersIn: string)
        return cs
    }
}

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