如何從Objective-C的NSString中獲取前N個單詞？

Question

什麼是最簡單的方式，給定的字符串：

NSString *str = @"Some really really long string is here and I just want the first 10 words, for example"; 

導致一個NSString與第一Ñ（例如，10）個字？

編輯：我也想確保，如果str大於N.

Answer 1

短。如果字是用空格分隔它不會失敗：

NSInteger nWords = 10; 
NSRange wordRange = NSMakeRange(0, nWords); 
NSArray *firstWords = [[str componentsSeparatedByString:@" "] subarrayWithRange:wordRange]; 

，如果你想打破所有空白：

NSCharacterSet *delimiterCharacterSet = [NSCharacterSet whitespaceAndNewlineCharacterSet]; 
NSArray *firstWords = [[str componentsSeparatedByCharactersInSet:delimiterCharacterSet] subarrayWithRange:wordRange]; 

然後，

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

Answer 2

儘管Barry Wark的代碼適用於英語，但它不是檢測單詞分隔符的首選方式。許多語言（如中文和日文）不會使用空格分隔單詞。例如，德國有許多化合物難以正確分離。

要使用什麼是CFStringTokenizer：

CFStringRef string; // Get string from somewhere 
CFLocaleRef locale = CFLocaleCopyCurrent(); 

CFStringTokenizerRef tokenizer = CFStringTokenizerCreate(kCFAllocatorDefault, string, CFRangeMake(0, CFStringGetLength(string)), kCFStringTokenizerUnitWord, locale); 

CFStringTokenizerTokenType tokenType = kCFStringTokenizerTokenNone; 
unsigned tokensFound = 0, desiredTokens = 10; // or the desired number of tokens 

while(kCFStringTokenizerTokenNone != (tokenType = CFStringTokenizerAdvanceToNextToken(tokenizer)) && tokensFound < desiredTokens) { 
    CFRange tokenRange = CFStringTokenizerGetCurrentTokenRange(tokenizer); 
    CFStringRef tokenValue = CFStringCreateWithSubstring(kCFAllocatorDefault, string, tokenRange); 

    // Do something with the token 
    CFShow(tokenValue); 

    CFRelease(tokenValue); 

    ++tokensFound; 
} 

// Clean up 
CFRelease(tokenizer); 
CFRelease(locale); 

Answer 3

基於巴里的回答，我寫了一個函數爲這個頁面的緣故（仍然給他SO信貸）

+ (NSString*)firstWords:(NSString*)theStr howMany:(NSInteger)maxWords { 

    NSArray *theWords = [theStr componentsSeparatedByString:@" "]; 
    if ([theWords count] < maxWords) { 
     maxWords = [theWords count]; 
    } 
    NSRange wordRange = NSMakeRange(0, maxWords - 1); 
    NSArray *firstWords = [theWords subarrayWithRange:wordRange];  
    return [firstWords componentsJoinedByString:@" "]; 
} 

Answer 4

這裏的我的解決方案，從這裏給出的答案派生，對於我自己的問題，從字符串中刪除第一個單詞...

NSMutableArray *words = [NSMutableArray arrayWithArray:[lowerString componentsSeparatedByString:@" "]]; 
[words removeObjectAtIndex:0]; 
return [words componentsJoinedByString:@" "];