从 NSString 中去除非字母数字字符

Question

我正在寻找一种快速简便的方法来从 NSString 中删除非字母数字字符。可能是使用 NSCharacterSet 的东西，但我累了，似乎没有任何东西返回只包含字符串中字母数字字符的字符串。

Answer 1

我们可以通过拆分然后合并来做到这一点。组件SeparatedByCharactersInSet 需要 OS X 10.5+：

NSCharacterSet *charactersToRemove = [[NSCharacterSet alphanumericCharacterSet] invertedSet];
NSString *strippedReplacement = [[someString componentsSeparatedByCharactersInSet:charactersToRemove] componentsJoinedByString:@""];

Answer 2

在 Swift 中，componentsJoinedByString 被 join(...) 替换，因此这里它只是用空格替换非字母数字字符。

let charactersToRemove = NSCharacterSet.alphanumericCharacterSet().invertedSet
let strippedReplacement = " ".join(someString.componentsSeparatedByCharactersInSet(charactersToRemove))

---

对于 Swift2 ...

var enteredByUser = field.text .. or whatever

let unsafeChars = NSCharacterSet.alphanumericCharacterSet().invertedSet

enteredByUser = enteredByUser
         .componentsSeparatedByCharactersInSet(unsafeChars)
         .joinWithSeparator("")

如果您只想删除一个字符，例如删除所有返回...

 enteredByUser = enteredByUser
         .componentsSeparatedByString("\n")
         .joinWithSeparator("")

Answer 3

我最后做的是创建一个 NSCharacterSet 和我发现的 -invertedSet 方法（令人惊奇的是，额外的一个小时的睡眠对于文档阅读能力有何影响）。下面是代码片段，假设 someString 是要从中删除非字母数字字符的字符串：

NSCharacterSet *charactersToRemove =
[[ NSCharacterSet alphanumericCharacterSet ] invertedSet ];

NSString *trimmedReplacement =
[ someString stringByTrimmingCharactersInSet:charactersToRemove ];

trimmedReplacement 将包含 someString 的字母数字字符。

Answer 4

已接受答案的 Swift 3 版本：

let unsafeChars = CharacterSet.alphanumerics.inverted
let myStrippedString = myString.components(separatedBy: unsafeChars).joined(separator: "")

Answer 5

Swift 5，扩展：

extension String {

    /// Will strip all non alpha characters from a string
    public var alpha: String {
        return components(separatedBy: CharacterSet.alphanumerics.inverted).joined()
    }
}

Answer 6

清理类别

我有一个方法调用 stringByStrippingCharactersInSet: 和 stringByCollapsingWhitespace ，可以方便地直接插入。

@implementation NSString (Cleanup)

- (NSString *)clp_stringByStrippingCharactersInSet:(NSCharacterSet *)set
{
    return [[self componentsSeparatedByCharactersInSet:set] componentsJoinedByString:@""];
}

- (NSString *)clp_stringByCollapsingWhitespace
{
    NSArray *components = [self componentsSeparatedByCharactersInSet:[NSCharacterSet whitespaceCharacterSet]];
    components = [components filteredArrayUsingPredicate:[NSPredicate predicateWithFormat:@"self <> ''"]];

    return [components componentsJoinedByString:@" "];
}

@end

Answer 7

以下是 Cameron 类别 的 Swift 版本作为扩展：

extension String {

    func stringByStrippingCharactersInSet(set:NSCharacterSet) -> String
    {
        return (self.componentsSeparatedByCharactersInSet(set) as NSArray).componentsJoinedByString("")
    }

    func stringByCollapsingWhitespace() -> String
    {
        var components:NSArray = self.componentsSeparatedByCharactersInSet(NSCharacterSet.whitespaceCharacterSet())
        let predicate = NSPredicate(format: "self <> ''", argumentArray: nil)
        components = components.filteredArrayUsingPredicate(predicate)

        return components.componentsJoinedByString(" ")
    }
}

Answer 8

我认为简单的循环执行时间会更快：

@implementation NSString(MyUtil)

- (NSString*) stripNonNumbers {
    NSMutableString* res = [NSMutableString new];
    //NSCharacterSet *numericSet = [NSCharacterSet decimalDigitCharacterSet];
    for ( int i=0; i < self.length; ++i ) {
        unichar c = [self characterAtIndex:i];
        if ( c >= '0' && c <= '9' ) // this looks cleaner, but a bit slower: [numericSet characterIsMember:c])
            [res appendFormat:@"%c", c];
    }
    return res;
}

@end

Answer 9

更有效的方法

+ (NSString *)alphanumericString:(NSString *)s {

    NSCharacterSet * charactersToRemove = [[NSCharacterSet alphanumericCharacterSet] invertedSet];
    NSMutableString * ms = [NSMutableString stringWithCapacity:[s length]];
    for (NSInteger i = 0; i < s.length; ++i) {
        unichar c = [s characterAtIndex:i];
        if (![charactersToRemove characterIsMember:c]) {
            [ms appendFormat:@"%c", c];
        }
    }
    return ms;

}

这是比提供的答案或作为类别

@implementation NSString (Alphanumeric)

- (NSString *)alphanumericString {

    NSCharacterSet * charactersToRemove = [[NSCharacterSet alphanumericCharacterSet] invertedSet];
    NSMutableString * ms = [NSMutableString stringWithCapacity:[self length]];
    for (NSInteger i = 0; i < self.length; ++i) {
        unichar c = [self characterAtIndex:i];
        if (![charactersToRemove characterIsMember:c]) {
            [ms appendFormat:@"%c", c];
        }
    }
    return ms;

}

@end