ios开发之NSString

初始化字符串：

- (instancetype)initWithCharactersNoCopy:(unichar *)characters length:(NSUInteger)length freeWhenDone:(BOOL)freeBuffer; /* "NoCopy" is a hint */- (instancetype)initWithCharacters:(const unichar *)characters length:(NSUInteger)length;- (nullable instancetype)initWithUTF8String:(const char *)nullTerminatedCString;- (instancetype)initWithString:(NSString *)aString;- (instancetype)initWithFormat:(NSString *)format, ... NS_FORMAT_FUNCTION(1,2);- (instancetype)initWithFormat:(NSString *)format arguments:(va_list)argList NS_FORMAT_FUNCTION(1,0);- (instancetype)initWithFormat:(NSString *)format locale:(nullable id)locale, ... NS_FORMAT_FUNCTION(1,3);- (instancetype)initWithFormat:(NSString *)format locale:(nullable id)locale arguments:(va_list)argList NS_FORMAT_FUNCTION(1,0);- (nullable instancetype)initWithData:(NSData *)data encoding:(NSStringEncoding)encoding;- (nullable instancetype)initWithBytes:(const void *)bytes length:(NSUInteger)len encoding:(NSStringEncoding)encoding;- (nullable instancetype)initWithBytesNoCopy:(void *)bytes length:(NSUInteger)len encoding:(NSStringEncoding)encoding freeWhenDone:(BOOL)freeBuffer;    /* "NoCopy" is a hint */- (nullable instancetype)initWithCString:(const char *)nullTerminatedCString encoding:(NSStringEncoding)encoding;- (nullable instancetype)initWithContentsOfURL:(NSURL *)url encoding:(NSStringEncoding)enc error:(NSError **)error;- (nullable instancetype)initWithContentsOfFile:(NSString *)path encoding:(NSStringEncoding)enc error:(NSError **)error;- (nullable instancetype)initWithContentsOfURL:(NSURL *)url usedEncoding:(nullable NSStringEncoding *)enc error:(NSError **)error;- (nullable instancetype)initWithContentsOfFile:(NSString *)path usedEncoding:(nullable NSStringEncoding *)enc error:(NSError **)error;

构建字符串

+ (instancetype)string;+ (instancetype)stringWithString:(NSString *)string;+ (instancetype)stringWithCharacters:(const unichar *)characters length:(NSUInteger)length;+ (nullable instancetype)stringWithUTF8String:(const char *)nullTerminatedCString;+ (instancetype)stringWithFormat:(NSString *)format, ... NS_FORMAT_FUNCTION(1,2);+ (instancetype)localizedStringWithFormat:(NSString *)format, ... NS_FORMAT_FUNCTION(1,2);+ (nullable instancetype)stringWithCString:(const char *)cString encoding:(NSStringEncoding)enc;+ (nullable instancetype)stringWithContentsOfURL:(NSURL *)url encoding:(NSStringEncoding)enc error:(NSError **)error;+ (nullable instancetype)stringWithContentsOfFile:(NSString *)path encoding:(NSStringEncoding)enc error:(NSError **)error;+ (nullable instancetype)stringWithContentsOfURL:(NSURL *)url usedEncoding:(nullable NSStringEncoding *)enc error:(NSError **)error;+ (nullable instancetype)stringWithContentsOfFile:(NSString *)path usedEncoding:(nullable NSStringEncoding *)enc error:(NSError **)error;

返回长度

@property (readonly) NSUInteger length;

返回下标对应的字符

- (unichar)characterAtIndex:(NSUInteger)index;

获取区间对应的字符数组

- (void)getCharacters:(unichar *)buffer range:(NSRange)range;

添加字符串

- (NSString *)stringByAppendingString:(NSString *)aString;- (NSString *)stringByAppendingFormat:(NSString *)format, ...;

截取字符串

- (NSString *)substringFromIndex:(NSUInteger)from;- (NSString *)substringToIndex:(NSUInteger)to;- (NSString *)substringWithRange:(NSRange)range;

比较字符串

- (NSComparisonResult)compare:(NSString *)string;- (NSComparisonResult)compare:(NSString *)string options:(NSStringCompareOptions)mask;- (NSComparisonResult)compare:(NSString *)string options:(NSStringCompareOptions)mask range:(NSRange)rangeOfReceiverToCompare;- (NSComparisonResult)compare:(NSString *)string options:(NSStringCompareOptions)mask range:(NSRange)rangeOfReceiverToCompare locale:(nullable id)locale;

字符串是否相同

- (BOOL)isEqualToString:(NSString *)aString;

是否以字符串开头

- (BOOL)hasPrefix:(NSString *)str;

是否以字符串结尾

- (BOOL)hasSuffix:(NSString *)str;

搜索字符串

- (NSRange)rangeOfString:(NSString *)searchString;- (NSRange)rangeOfString:(NSString *)searchString options:(NSStringCompareOptions)mask;- (NSRange)rangeOfString:(NSString *)searchString options:(NSStringCompareOptions)mask range:(NSRange)rangeOfReceiverToSearch;- (NSRange)rangeOfString:(NSString *)searchString options:(NSStringCompareOptions)mask range:(NSRange)rangeOfReceiverToSearch locale:(nullable NSLocale *)locale

搜索字符序列

- (NSRange)rangeOfCharacterFromSet:(NSCharacterSet *)searchSet;- (NSRange)rangeOfCharacterFromSet:(NSCharacterSet *)searchSet options:(NSStringCompareOptions)mask;- (NSRange)rangeOfCharacterFromSet:(NSCharacterSet *)searchSet options:(NSStringCompareOptions)mask range:(NSRange)rangeOfReceiverToSearch;

小写字符转大写

@property (readonly, copy) NSString *lowercaseString;

大写字符转小写

@property (readonly, copy) NSString *uppercaseString;