一、大小写转换
1、- (NSString *)uppercaseString; 所有字符转化为大写
2、- (NSString *)lowercaseString; 所有字符转化为小写
3、- (NSString *)capitalizedString; 所有单词首字母转化大写

NSLog(@"%@", [demoTwo uppercaseString]);
NSLog(@"%@", [demoTwo lowercaseString]);
NSLog(@"%@", [demoTwo capitalizedString]);


 GOOD MORNING
 good morning
Good Morning

五、- (NSRange)lineRangeForRange:(NSRange)range;返回字符串指定段的位置和长度 
NSLog(@"%ld", [demoTwo lineRangeForRange:NSMakeRange(7, 2)].length);
 12


六、- (void)getParagraphStart:(NSUInteger *)startPtr end:(NSUInteger *)parEndPtr contentsEnd:(NSUInteger *)contentsEndPtr forRange:(NSRange)range;  指定段分段取字符串

NSUInteger paraStart, paraEnd, contEnd;
NSString *aString1 = @"Apple\u2028Orange\u2029Banana\r\nLemon";
[aString1 getParagraphStart:&paraStart end:&paraEnd contentsEnd:&contEnd forRange:NSMakeRange(14, 1)] ;
NSLog(@"%@", [NSString stringWithFormat:@"ParagraphStart=%d, ParagraphEnd=%d, ContentsEnd=%d", paraStart, paraEnd, contEnd]);

八、- (NSString *)description;  返回字符串
NSLog(@"%@", [demoTwo description]);
 good morning

十、编码处理
- (NSStringEncoding)fastestEncoding;     // 字符串最快编码值
- (NSStringEncoding)smallestEncoding;    //  字符串最小编码值
- (NSData *)dataUsingEncoding:(NSStringEncoding)encoding allowLossyConversion:(BOOL)lossy;   // 返回指定编码的NSData对象，可以选择无损转化
- (NSData *)dataUsingEncoding:(NSStringEncoding)encoding;                                    // 返回指定编码的NSData对象
- (BOOL)canBeConvertedToEncoding:(NSStringEncoding)encoding;     //判断是否可以无损转化编码

NSLog(@"%lu", [demoTwo fastestEncoding]);
NSLog(@"%lu", [demo smallestEncoding]);

NSLog(@"%@", [demoTwo dataUsingEncoding:NSShiftJISStringEncoding allowLossyConversion:YES]);
NSLog(@"%@", [demoTwo dataUsingEncoding:NSWindowsCP1251StringEncoding]);
NSLog(@"%d", [demoTwo canBeConvertedToEncoding:NSMacOSRomanStringEncoding]);

 30
 30
<676f6f64 206d6f72 6e696e67>
 <676f6f64 206d6f72 6e696e67>
 1