将白色空间的序列折叠成单个字符和修剪字符串

Question

请考虑以下示例:

"    Hello      this  is a   long       string!   "

我想将其转换为:

"Hello this is a long string!"

Answer 1

OS X 10.7+和iOS 3.2+

使用hfossli提供的本机regexp解决方案.

除此以外

使用您喜欢的regexp库或使用以下Cocoa原生解决方案:

NSString *theString = @"    Hello      this  is a   long       string!   ";

NSCharacterSet *whitespaces = [NSCharacterSet whitespaceCharacterSet];
NSPredicate *noEmptyStrings = [NSPredicate predicateWithFormat:@"SELF != ''"];

NSArray *parts = [theString componentsSeparatedByCharactersInSet:whitespaces];
NSArray *filteredArray = [parts filteredArrayUsingPredicate:noEmptyStrings];
theString = [filteredArray componentsJoinedByString:@" "];

Answer 2

正则表达式和NSCharacterSet可以帮助您.此解决方案修剪前导和尾随空白以及多个空白.

NSString *original = @"    Hello      this  is a   long       string!   ";

NSString *squashed = [original stringByReplacingOccurrencesOfString:@"[ ]+"
                                                         withString:@" "
                                                            options:NSRegularExpressionSearch
                                                              range:NSMakeRange(0, original.length)];

NSString *final = [squashed stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];

记录final给出

"Hello this is a long string!"

可能的替代正则表达式模式:

• 仅替换空间: [ ]+
• 替换空格和标签: [ \\t]+
• 替换空格,制表符和换行符: \\s+

性能破坏

• 此解决方案:7.6秒
• 拆分,过滤,加入(GeorgSchölly):13.7秒

易于扩展,性能,代码行数和创建的对象数使该解决方案合适.

Answer 3

实际上,有一个非常简单的解决方案:

NSString *string = @" spaces in front and at the end ";
NSString *trimmedString = [string stringByTrimmingCharactersInSet:
                                  [NSCharacterSet whitespaceAndNewlineCharacterSet]];
NSLog(@"%@", trimmedString)

(来源)

Answer 4

使用正则表达式,但不需要任何外部框架:

NSString *theString = @"    Hello      this  is a   long       string!   ";

theString = [theString stringByReplacingOccurrencesOfString:@" +" withString:@" "
                       options:NSRegularExpressionSearch
                       range:NSMakeRange(0, theString.length)];

Answer 5

一线解决方案:

NSString *whitespaceString = @" String with whitespaces ";

NSString *trimmedString = [whitespaceString
        stringByReplacingOccurrencesOfString:@" " withString:@""];

Answer 6

这应该做到......

NSString *s = @"this is    a  string    with lots  of     white space";
NSArray *comps = [s componentsSeparatedByCharactersInSet:[NSCharacterSet whitespaceCharacterSet]];

NSMutableArray *words = [NSMutableArray array];
for(NSString *comp in comps) {
  if([comp length] > 1)) {
    [words addObject:comp];
  }
}

NSString *result = [words componentsJoinedByString:@" "];

Answer 7

这是扩展程序的片段NSString，其中"self"是NSString实例。它可用于通过传入[NSCharacterSet whitespaceAndNewlineCharacterSet]和' '两个参数来将连续的空白折叠为单个空格。

- (NSString *) stringCollapsingCharacterSet: (NSCharacterSet *) characterSet toCharacter: (unichar) ch {
int fullLength = [self length];
int length = 0;
unichar *newString = malloc(sizeof(unichar) * (fullLength + 1));

BOOL isInCharset = NO;
for (int i = 0; i < fullLength; i++) {
    unichar thisChar = [self characterAtIndex: i];

    if ([characterSet characterIsMember: thisChar]) {
        isInCharset = YES;
    }
    else {
        if (isInCharset) {
            newString[length++] = ch;
        }

        newString[length++] = thisChar;
        isInCharset = NO;
    }
}

newString[length] = '\0';

NSString *result = [NSString stringWithCharacters: newString length: length];

free(newString);

return result;
}