NSString *temp = @"Contrafibularity";

const char *cString = [@"Hello, world" UTF8String];

1.Try stringWithContentsOfFile:usedEncoding:error: orinitWithContentsOfFile:usedEncoding:error: (or the URL-based equivalents).These methods try to determine the encoding of the resource, and if successful return by reference the encoding used.
2.If (1) fails, try to read the resource by specifying UTF-8 as the encoding.
3.If (2) fails, try an appropriate legacy encoding. "Appropriate" here depends a bit on circumstances;it might be the default C string encoding, it might be ISO or Windows Latin 1, or something else,  depending on where your data are coming from.
4.Finally, you can try NSAttributedString's loading methods from the Application Kit (such asinitWithURL:options:documentAttributes:error:).These methods attempt to load plain text files, and return the encoding used.They can be used on more-or-less arbitrary text documents, and are worth considering if your application has no special expertise in text.  They might not be as appropriate for Foundation-level tools or documents that are not natural-language text.

NSString *string = @"Product: Acme Potato Peeler; Cost: 0.98 73\n\Product: Chef Pierre Pasta Fork; Cost: 0.75 19\n\Product:Chef Pierre Colander; Cost: 1.27 2\n";
NSCharacterSet *semicolonSet;
NSScanner *theScanner;NSString *PRODUCT = @"Product:";
NSString *COST = @"Cost:";NSString *productName;
float productCost;NSInteger productSold;
semicolonSet = [NSCharacterSet characterSetWithCharactersInString:@";"];
theScanner = [NSScanner scannerWithString:string];while ([theScanner isAtEnd] == NO)
{if ([theScanner scanString:PRODUCT intoString:NULL] &&[theScanner scanUpToCharactersFromSet:semicolonSet intoString:&productName] &&[theScanner scanString:@";" intoString:NULL] &&[theScanner scanString:COST intoString:NULL] &&[theScanner scanFloat:&productCost] &&[theScanner scanInteger:&productSold]){NSLog(@"Sales of %@: $%1.2f", productName, productCost * productSold);}
} 

NSString *path = @"/usr/bin/./grep";
NSString *standardizedPath = [path stringByStandardizingPath];
// standardizedPath: /usr/bin/grep

补全相对路径：

NSString *meHome = [@"~me" stringByExpandingTildeInPath];
// meHome = @"/Users/me"

获取Document目录：

NSString *documentsDirectory;
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);if ([paths count] > 0) {documentsDirectory = [paths objectAtIndex:0];
}

路径Component操作：　　　　　　　　文件名匹配搜索：假设路径“~/Demo/”下有如下文件ReadMe.txt readme.html readme.rtf recondite.txt test.txt 

NSString *partialPath = @"~/Demo/r";
NSString *longestCompletion;
NSArray *outputArray;unsigned allMatches = [partialPath completePathIntoString:&longestCompletioncaseSensitive:NOmatchesIntoArray:&outputArrayfilterTypes:NULL];// allMatches = 3
// longestCompletion = @"~/Demo/re"
// outputArray = (@"~/Demo/readme.html", "~/Demo/readme.rtf", "~/Demo/recondite.txt"