blocks|key|1365544|text|OS+X+10.7%2B和iOS+3.2%2B|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1365545|使用hfossli提供的原生regexp+solution。|offset|length|1365546|否则|1365547|使用您最喜欢的regexp库或使用以下Cocoa原生解决方案：|1365548|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:@"+"];|code-block|syntax|javascript|1365549|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/a/18083852/24587^0|0|E|F|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|X|8|@]|9|@$D|Y|E|Z|1|10]]|A|$]]|$1|F|3|G|5|6|7|11|8|@]|9|@]|A|$]]|$1|H|3|I|5|6|7|12|8|@]|9|@]|A|$]]|$1|J|3|K|5|L|7|13|8|@]|9|@]|A|$M|N]]|$1|O|3|-4|5|6|7|14|8|@]|9|@]|A|$]]]|P|$Q|$5|R|S|T|A|$U|V]]]]

<h1>OS X 10.7+ and iOS 3.2+</h1>

Use the native <a href="https://stackoverflow.com/a/18083852/24587">regexp solution</a> provided by hfossli.

<h1>Otherwise</h1>

Either use your favorite regexp library or use the following Cocoa-native solution:

<pre><code>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:@" "];
</code></pre>

blocks|key|1580587|text|实际上，有一个非常简单的解决方案：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1580588|NSString+*string+=+@"+spaces+in+front+and+at+the+end+";
NSString+*trimmedString+=+[string+stringByTrimmingCharactersInSet:
++++++++++++++++++++++++++++++++++[NSCharacterSet+whitespaceAndNewlineCharacterSet]];
NSLog(@"%25@",+trimmedString)|code-block|syntax|javascript|1580589|(Source)|offset|length|1580590|entityMap|0|LINK|mutability|MUTABLE|url|http://www.drobnik.com/touch/2009/01/remove-whitespace-from-nsstring/^0|0|0|1|6|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@$I|V|J|W|1|X]]|A|$]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|R]]]]

Actually, there's a very simple solution to that:

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

(<a href="http://www.drobnik.com/touch/2009/01/remove-whitespace-from-nsstring/" rel="nofollow noreferrer">Source</a>)

blocks|key|1580764|text|使用正则表达式，但不需要任何外部框架：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1580765|NSString+*theString+=+@"++++Hello++++++this++is+a+++long+++++++string!+++";

theString+=+[theString+stringByReplacingOccurrencesOfString:@"+%2B"+withString:@"+"
+++++++++++++++++++++++options:NSRegularExpressionSearch
+++++++++++++++++++++++range:NSMakeRange(0,+theString.length)];|code-block|syntax|javascript|1580766|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

With a regex, but without the need for any external framework:

<pre><code>NSString *theString = @" Hello this is a long string! ";

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

blocks|key|1365572|text|单行解决方案：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1365573|NSString+*whitespaceString+=+@"+String+with+whitespaces+";

NSString+*trimmedString+=+[whitespaceString
++++++++stringByReplacingOccurrencesOfString:@"+"+withString:@""];|code-block|syntax|javascript|1365574|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

A one line solution:

<pre><code>NSString *whitespaceString = @" String with whitespaces ";

NSString *trimmedString = [whitespaceString
 stringByReplacingOccurrencesOfString:@" " withString:@""];
</code></pre>

blocks|key|1365355|text|这个应该可以..。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1365356|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:@"+"];|code-block|syntax|javascript|1365357|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

This should do it... 

<pre><code>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] &gt; 1)) {
 [words addObject:comp];
 }
}

NSString *result = [words componentsJoinedByString:@" "];
</code></pre>

blocks|key|1365385|text|正则表达式的另一个选择是RegexKitLite，它很容易嵌入到iPhone项目中：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1365386|[theString+stringByReplacingOccurencesOfRegex:@"+%2B"+withString:@"+"];|code-block|syntax|javascript|1365387|entityMap|0|LINK|mutability|MUTABLE|url|http://regexkit.sourceforge.net/RegexKitLite/index.html^0|C|C|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

Another option for regex is <a href="http://regexkit.sourceforge.net/RegexKitLite/index.html" rel="nofollow noreferrer">RegexKitLite</a>, which is very easy to embed in an iPhone project:

<pre><code>[theString stringByReplacingOccurencesOfRegex:@" +" withString:@" "];
</code></pre>

blocks|key|1580465|text|下面是NSString扩展的一个片段，其中"self"是NSString实例。通过将[NSCharacterSet+whitespaceAndNewlineCharacterSet]和'+'传递给两个参数，它可用于将连续的空格折叠为一个空格。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1580466|-+(NSString+*)+stringCollapsingCharacterSet:+(NSCharacterSet+*)+characterSet+toCharacter:+(unichar)+ch+{
int+fullLength+=+[self+length];
int+length+=+0;
unichar+*newString+=+malloc(sizeof(unichar)+*+(fullLength+%2B+1));

BOOL+isInCharset+=+NO;
for+(int+i+=+0;+i+<+fullLength;+i%2B%2B)+{
++++unichar+thisChar+=+[self+characterAtIndex:+i];

++++if+([characterSet+characterIsMember:+thisChar])+{
++++++++isInCharset+=+YES;
++++}
++++else+{
++++++++if+(isInCharset)+{
++++++++++++newString[length%2B%2B]+=+ch;
++++++++}

++++++++newString[length%2B%2B]+=+thisChar;
++++++++isInCharset+=+NO;
++++}
}

newString[length]+=+'\0';

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

free(newString);

return+result;
}|code-block|syntax|javascript|1580467|entityMap^0|3|8|L|6|S|8|16|1D|2K|3|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]|$9|P|A|Q|B|C]|$9|R|A|S|B|C]|$9|T|A|U|B|C]|$9|V|A|W|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|X|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Y|8|@]|D|@]|E|$]]]|L|$]]

Here's a snippet from an <code>NSString</code> extension, where <code>"self"</code> is the <code>NSString</code> instance. It can be used to collapse contiguous whitespace into a single space by passing in <code>[NSCharacterSet whitespaceAndNewlineCharacterSet]</code> and <code>' '</code> to the two arguments.

<pre><code>- (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 &lt; 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;
}
</code></pre>

blocks|key|1365764|text|尝尝这个|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1365765|NSString+*theString+=+@"++++Hello++++++this++is+a+++long+++++++string!+++";

while+([theString+rangeOfString:@"++"].location+!=+NSNotFound)+{
++++theString+=+[theString+stringByReplacingOccurrencesOfString:@"++"+withString:@"+"];
}|code-block|syntax|javascript|1365766|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Try This

<pre><code>NSString *theString = @" Hello this is a long string! ";

while ([theString rangeOfString:@" "].location != NSNotFound) {
 theString = [theString stringByReplacingOccurrencesOfString:@" " withString:@" "];
}
</code></pre>

blocks|key|1580880|text|根据@Mathieu+Godart的说法是最好的答案，但是缺少一些行，所有的答案只是减少单词之间的空格，但是如果有制表符或在位置空间中有制表符，就像这样：“this+is+text+\t，and\+three，so”在三行代码中，我们将:我们想要的字符串减少空白|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1580881|NSString+*+str_aLine+=+@"++++this+is+text+\t+,+and\tTab+between++++++,+so+on++++";
//+replace+tabs+to+space
str_aLine+=+[str_aLine+stringByReplacingOccurrencesOfString:@"\t"+withString:@"+"];
//+reduce+spaces+to+one+space
str_aLine+=+[str_aLine+stringByReplacingOccurrencesOfString:@"+%2B"+withString:@"+"
++++++++++++++++++++++++++++++++++++++++++++++++++++options:NSRegularExpressionSearch
++++++++++++++++++++++++++++++++++++++++++++++++++++++range:NSMakeRange(0,+str_aLine.length)];
//+trim+begin+and+end+from+white+spaces
str_aLine+=+[str_aLine+stringByTrimmingCharactersInSet:[NSCharacterSet+whitespaceAndNewlineCharacterSet]];|code-block|syntax|javascript|1580882|结果是|1580883|"this+is+text+,+and+Tab+between+,+so+on"|1580884|如果不替换选项卡，结果将为：|1580885|"this+is+text++++,+and++Tab+between+,+so+on"|1580886|entityMap^0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|S|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|U|8|@]|9|@]|A|$]]|$1|M|3|N|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|O|3|-4|5|6|7|W|8|@]|9|@]|A|$]]]|P|$]]

according from @Mathieu Godart is best answer, but some line is missing , all answers just reduce space between words , but when if have tabs or have tab in place space , like this:
" this is text \t , and\tTab between , so on "
in three line code we will :
the string we want reduce white spaces

<pre><code>NSString * str_aLine = @" this is text \t , and\tTab between , so on ";
// replace tabs to space
str_aLine = [str_aLine stringByReplacingOccurrencesOfString:@"\t" withString:@" "];
// reduce spaces to one space
str_aLine = [str_aLine stringByReplacingOccurrencesOfString:@" +" withString:@" "
 options:NSRegularExpressionSearch
 range:NSMakeRange(0, str_aLine.length)];
// trim begin and end from white spaces
str_aLine = [str_aLine stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
</code></pre>

the result is

<pre><code>"this is text , and Tab between , so on"
</code></pre>

without replacing tab the resul will be:

<pre><code>"this is text , and Tab between , so on"
</code></pre>

blocks|key|1365810|text|你也可以使用一个简单的while参数。这里面没有RegEx的魔力，所以将来可能更容易理解和修改：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1365811|while([yourNSStringObject+replaceOccurrencesOfString:@"++"
+++++++++++++++++++++++++withString:@"+"
+++++++++++++++++++++++++options:0
+++++++++++++++++++++++++range:NSMakeRange(0,+[yourNSStringObject+length])]+>+0);|code-block|syntax|javascript|1365812|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

You can also use a simple while argument. There is no RegEx magic in there, so maybe it is easier to understand and alter in the future:

<pre><code>while([yourNSStringObject replaceOccurrencesOfString:@" "
 withString:@" "
 options:0
 range:NSMakeRange(0, [yourNSStringObject length])] &gt; 0);
</code></pre>

Consider the following example:

<pre><code>" Hello this is a long string! "
</code></pre>

I want to convert that to:

<pre><code>"Hello this is a long string!"
</code></pre>

Collapse sequences of white space into a single character and trim string

考虑以下示例："    Hello      this  is a   long       string!   "我想把它转换成："Hello this is a long string!"

问将空白序列折叠为单个字符并修剪字符串
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回答 10

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问将空白序列折叠为单个字符并修剪字符串EN

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问将空白序列折叠为单个字符并修剪字符串
EN