前言

NSString虽然我们每天都用也很简单，这里我就总结一下，做到NSString简单细说深说，这里首先要对整个NSString有整体的感知和认识，详细的以后会续写，不对的地方大家批评补充。

苹果开发文档

NSString功能架构

下面我们开始，首先看一下NSString有哪些功能相对应的属性和类。

功能	方法名
简单实例化	1. + (instancetype) string;
	2. - (instancetype) init
	3. - (instancetype) initWithBytes:(const void *)bytes length:(NSUInteger)len encoding:(NSStringEncoding)encoding;
	4. - (instancetype) initWithBytesNoCopy:(void *)bytes length:(NSUInteger)len encoding:(NSStringEncoding)encoding freeWhenDone:(BOOL)freeBuffer;
	5. - (instancetype) initWithCharacters:(const unichar *)characters length:(NSUInteger)length;
	6. - (instancetype) initWithCharactersNoCopy:(unichar *)characters length:(NSUInteger)length freeWhenDone:(BOOL)freeBuffer;
	7. - (instancetype) initWithString:(NSString *)aString;
	8. - (instancetype) initWithCString:(const char *)nullTerminatedCString encoding:(NSStringEncoding)encoding;
	9. - (instancetype) initWithUTF8String:(const char *)nullTerminatedCString;
	10. - (instancetype) initWithFormat:(NSString *)format, ...;
	11. - (instancetype) initWithFormat:(NSString *)format arguments:(va_list)argList;
	12. - (instancetype) initWithFormat:(NSString *)format locale:(id)locale, ...;
	13. - (instancetype) initWithFormat:(NSString *)format locale:(id)locale arguments:(va_list)argList;
	14. - (instancetype) initWithData:(NSData *)data encoding:(NSStringEncoding)encoding;
	15. + (instancetype) stringWithFormat:(NSString *)format, ...;
	16. + (instancetype) localizedStringWithFormat:(NSString *)format, ...;
	17. + (NSString ) localizedUserNotificationStringForKey:(NSString)key arguments:(NSArray*)arguments;
	18. + (instancetype) stringWithCharacters:(const unichar *)characters length:(NSUInteger)length;
	19. + (instancetype) stringWithString:(NSString *)string;
	20. + (instancetype) stringWithCString:(const char *)cString encoding:(NSStringEncoding)enc;
	21. + (instancetype) stringWithUTF8String:(const char *)nullTerminatedCString;
文件实例化	1. + (instancetype) stringWithContentsOfFile:(NSString )path encoding:(NSStringEncoding)enc error:(NSError _Nullable *)error;
	2. - (instancetype) initWithContentsOfFile:(NSString )path encoding:(NSStringEncoding)enc error:(NSError _Nullable *)error;
	3. + (instancetype) stringWithContentsOfFile:(NSString )path usedEncoding:(NSStringEncoding )enc error:(NSError * _Nullable *)error;
	4. - (instancetype) initWithContentsOfFile:(NSString )path usedEncoding:(NSStringEncoding )enc error:(NSError * _Nullable *)error;
URL实例化	1. + (instancetype) stringWithContentsOfURL:(NSURL)url encoding:(NSStringEncoding)enc error:(NSError _Nullable *)error;
	2. - (instancetype) initWithContentsOfURL:(NSURL )url encoding:(NSStringEncoding)enc error:(NSError _Nullable *)error;
	3. + (instancetype) stringWithContentsOfURL:(NSURL )url usedEncoding:(NSStringEncoding )enc error:(NSError * _Nullable *)error;
	4. - (instancetype) initWithContentsOfURL:(NSURL )url usedEncoding:(NSStringEncoding )enc error:(NSError * _Nullable *)error;
写向文件和URL	1. - (BOOL) writeToFile:(NSString )path atomically:(BOOL)useAuxiliaryFile encoding:(NSStringEncoding)enc error:(NSError _Nullable *)error;
	2. - (BOOL) writeToURL:(NSURL )url atomically:(BOOL)useAuxiliaryFile encoding:(NSStringEncoding)enc error:(NSError _Nullable *)error;
获取字符串长度	1. @property(readonly) NSUInteger length;
	2. - (NSUInteger) lengthOfBytesUsingEncoding:(NSStringEncoding)enc;
	3. - (NSUInteger) maximumLengthOfBytesUsingEncoding:(NSStringEncoding)enc;
获取字符字节	1. - (unichar) characterAtIndex:(NSUInteger)index;
	2. - (void) getCharacters:(unichar *)buffer range:(NSRange)range;
	3. - (BOOL) getBytes:(void )buffer maxLength:(NSUInteger)maxBufferCount usedLength:(NSUInteger )usedBufferCount encoding:(NSStringEncoding)encoding options:(NSStringEncodingConversionOptions)options range:(NSRange)range remainingRange:(NSRangePointer)leftover;
获取C字符串	1. - (const char *) cStringUsingEncoding:(NSStringEncoding)encoding;
	2. - (BOOL) getCString:(char *)buffer maxLength:(NSUInteger)maxBufferCount encoding:(NSStringEncoding)encoding;
	3. @property(readonly) const char *UTF8String;
字符串比较	1. - (NSComparisonResult)caseInsensitiveCompare:(NSString *)string;
	2. - (NSComparisonResult) localizedCaseInsensitiveCompare:(NSString *)string;
	3. - (NSComparisonResult) compare:(NSString *)string;
	4. - (NSComparisonResult) localizedCompare:(NSString *)string;
	5. - (NSComparisonResult) compare:(NSString *)string options:(NSStringCompareOptions)mask;
	6. - (NSComparisonResult) compare:(NSString *)string options:(NSStringCompareOptions)mask range:(NSRange)rangeOfReceiverToCompare;
	7. - (NSComparisonResult) compare:(NSString *)string options:(NSStringCompareOptions)mask range:(NSRange)rangeOfReceiverToCompare locale:(id)locale;
	8. - (NSComparisonResult) localizedStandardCompare:(NSString *)string;
	9. - (BOOL) hasPrefix:(NSString *)str;
	10. - (BOOL) hasSuffix:(NSString *)str;
	11. - (BOOL) isEqualToString:(NSString *)aString;
	12. @property(readonly) NSUInteger hash;
字符串的合并	1. - (NSString ) stringByAppendingFormat:(NSString )format, ...;
	2. - (NSString )stringByAppendingString:(NSString )aString;
	3. - (NSString ) stringByPaddingToLength:(NSUInteger)newLength withString:(NSString )padString startingAtIndex:(NSUInteger)padIndex;
字符串的分割	1. - (NSArray ) componentsSeparatedByString:(NSString )separator;
	2. - (NSArray ) componentsSeparatedByCharactersInSet:(NSCharacterSet )separator;
	3. - (NSString ) stringByTrimmingCharactersInSet:(NSCharacterSet )set;
	4. - (NSString *) substringFromIndex:(NSUInteger)from;
	5. - (NSString *) substringWithRange:(NSRange)range;
	6. - (NSString *) substringToIndex:(NSUInteger)to;
字符串的查询	1. - (BOOL) containsString:(NSString *)str;
	2. - (BOOL) localizedCaseInsensitiveContainsString:(NSString *)str;
	3. - (BOOL) localizedStandardContainsString:(NSString *)str;
	4. - (NSRange) rangeOfCharacterFromSet:(NSCharacterSet *)searchSet;
	5. - (NSRange) rangeOfCharacterFromSet:(NSCharacterSet *) searchSet options:(NSStringCompareOptions)mask;
	6. - (NSRange) rangeOfCharacterFromSet:(NSCharacterSet *)searchSet options:(NSStringCompareOptions)mask range:(NSRange)rangeOfReceiverToSearch;
	7. - (NSRange) rangeOfString:(NSString *)searchString;
	8. - (NSRange) rangeOfString:(NSString *)searchString options:(NSStringCompareOptions)mask;
	9. - (NSRange) rangeOfString:(NSString *)searchString options:(NSStringCompareOptions)mask range:(NSRange)rangeOfReceiverToSearch;
	10. - (NSRange) rangeOfString:(NSString )searchString options:(NSStringCompareOptions)mask range:(NSRange)rangeOfReceiverToSearch locale:(NSLocale )locale;
	11. - (NSRange) localizedStandardRangeOfString:(NSString *)str;
	12. - (void) enumerateLinesUsingBlock:(void (^)(NSString line, BOOL stop))block;
	13. - (void) enumerateSubstringsInRange:(NSRange)range options:(NSStringEnumerationOptions)opts usingBlock:(void (^)(NSString substring, NSRange substringRange, NSRange enclosingRange, BOOL stop))block;
子字符串替换	1. - (NSString ) stringByReplacingOccurrencesOfString:(NSString )target withString:(NSString *)replacement;
	2. - (NSString ) stringByReplacingOccurrencesOfString:(NSString )target withString:(NSString *)replacement options:(NSStringCompareOptions)options range:(NSRange)searchRange;
	3. - (NSString ) stringByReplacingCharactersInRange:(NSRange)range withString:(NSString )replacement;
线和段落区间	1. - (void) getLineStart:(NSUInteger )startPtr end:(NSUInteger )lineEndPtr contentsEnd:(NSUInteger *)contentsEndPtr forRange:(NSRange)range;
	2. - (NSRange) lineRangeForRange:(NSRange)range;
	3. - (void) getParagraphStart:(NSUInteger )startPtr end:(NSUInteger )parEndPtr contentsEnd:(NSUInteger *)contentsEndPtr forRange:(NSRange)range;
	4. - (NSRange) paragraphRangeForRange:(NSRange)range;
返回给定区间	1. - (NSRange) rangeOfComposedCharacterSequenceAtIndex:(NSUInteger)index;
	2. - (NSRange) rangeOfComposedCharacterSequencesForRange:(NSRange)range;
转化属性列表	1. - (id) propertyList;
	2. - (NSDictionary *) propertyListFromStringsFileFormat;
画字符串	1. - (void) drawAtPoint:(CGPoint)point withAttributes:(NSDictionary *)attrs;
	2. - (void) drawInRect:(CGRect)rect withAttributes:(NSDictionary *)attrs;
	3. - (void) drawWithRect:(CGRect)rect options:(NSStringDrawingOptions)options attributes:(NSDictionary )attributes context:(NSStringDrawingContext )context;
	4. - (CGRect) boundingRectWithSize:(CGSize)size options:(NSStringDrawingOptions)options attributes:(NSDictionary )attributes context:(NSStringDrawingContext )context;
	5. - (CGSize) sizeWithAttributes:(NSDictionary *)attrs;
折叠	1. - (NSString ) stringByFoldingWithOptions:(NSStringCompareOptions)options locale:(NSLocale )locale;
字符串前缀分享	1. - (NSString ) commonPrefixWithString:(NSString )str options:(NSStringCompareOptions)mask;
形改变	1. @property(readonly, copy) NSString *lowercaseString;
	2. @property(readonly, copy) NSString *localizedLowercaseString;
	3. - (NSString )lowercaseStringWithLocale:(NSLocale )locale;
	4. @property(readonly, copy) NSString *uppercaseString;
	5. @property(readonly, copy) NSString *localizedUppercaseString;
	6. - (NSString ) uppercaseStringWithLocale:(NSLocale )locale;
	7. @property(readonly, copy) NSString *capitalizedString;
	8. @property(readonly, copy) NSString *localizedCapitalizedString;
	9. - (NSString ) capitalizedStringWithLocale:(NSLocale )locale;
映射	1. @property(readonly, copy) NSString *decomposedStringWithCanonicalMapping;
	2. @property(readonly, copy) NSString *decomposedStringWithCompatibilityMapping;
	3. @property(readonly, copy) NSString *precomposedStringWithCanonicalMapping;
	4. @property(readonly, copy) NSString *precomposedStringWithCompatibilityMapping;
获取数值	1. @property(readonly) double doubleValue;
	2. @property(readonly) float floatValue;
	3. @property(readonly) int intValue;
	4. @property(readonly) NSInteger integerValue;
	5. @property(readonly) long long longLongValue;
	6. @property(readonly) BOOL boolValue;
编码	1. + (NSStringEncoding) stringEncodingForData:(NSData )data encodingOptions:(NSDictionary )opts convertedString:(NSString * _Nullable )string usedLossyConversion:(BOOL )usedLossyConversion;
	2. + (NSString *) localizedNameOfStringEncoding:(NSStringEncoding)encoding;
	3. - (BOOL) canBeConvertedToEncoding:(NSStringEncoding)encoding;
	4. - (NSData *) dataUsingEncoding:(NSStringEncoding)encoding;
	5. - (NSData *) dataUsingEncoding:(NSStringEncoding)encoding allowLossyConversion:(BOOL)lossy;
	6. @property(readonly, copy) NSString *description;
	7. @property(readonly) NSStringEncoding fastestEncoding;
	8. @property(readonly) NSStringEncoding smallestEncoding;
路经相关	1. + (NSString ) pathWithComponents:(NSArray )components;
	2. @property(readonly, copy) NSArray *pathComponents;
	3. - (NSUInteger) completePathIntoString:(NSString * _Nullable )outputName caseSensitive:(BOOL)flag matchesIntoArray:(NSArray _Nullable )outputArray filterTypes:(NSArray )filterTypes;
	4. @property(readonly) const char *fileSystemRepresentation;
	5. - (BOOL) getFileSystemRepresentation:(char *)cname maxLength:(NSUInteger)max;
	6. @property(getter=isAbsolutePath, readonly) BOOL absolutePath;
	7. @property(readonly, copy) NSString *lastPathComponent;
	8. @property(readonly, copy) NSString *pathExtension;
	9. @property(readonly, copy) NSString *stringByAbbreviatingWithTildeInPath;
	10. - (NSString ) stringByAppendingPathComponent:(NSString )str;
	11.- (NSString ) stringByAppendingPathExtension:(NSString )str;
	12.@property(readonly, copy) NSString *stringByDeletingLastPathComponent;
	13.@property(readonly, copy) NSString *stringByDeletingPathExtension;
	14.@property(readonly, copy) NSString *stringByExpandingTildeInPath;
	15.@property(readonly, copy) NSString *stringByResolvingSymlinksInPath;
	16.@property(readonly, copy) NSString *stringByStandardizingPath;
	17.- (NSArray )stringsByAppendingPaths:(NSArray )paths;
URL相关	1.- (NSString ) stringByAddingPercentEncodingWithAllowedCharacters:(NSCharacterSet )allowedCharacters;
	2.@property(readonly, copy) NSString *stringByRemovingPercentEncoding;
语言标记	1.- (void) enumerateLinguisticTagsInRange:(NSRange)range scheme:(NSString )tagScheme options:(NSLinguisticTaggerOptions)opts orthography:(NSOrthography )orthography usingBlock:(void (^)(NSString tag, NSRange tokenRange, NSRange sentenceRange, BOOL stop))block;
	2.- (NSArray ) linguisticTagsInRange:(NSRange)range scheme:(NSString )tagScheme options:(NSLinguisticTaggerOptions)opts orthography:(NSOrthography )orthography tokenRanges:(NSArray _Nullable *)tokenRanges;