NSString类详解

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说到字符串NSString肯定每个开发IOS的都用过，它是Foundation框架下的一个核心处理字符串的类，掌握它非常有用。

1.属性：

最直接的属性有length,字符串长度

2.字符串的获取

//截取指定位置之后的字符串- (NSString *)substringFromIndex:(NSUInteger)from;//从0下标开始截取到指定位置的字符串- (NSString *)substringToIndex:(NSUInteger)to;//截取指定范围的字符串- (NSString *)substringWithRange:(NSRange)range;//截取字符串指定范围的字符- (void)getCharacters:(unichar *)buffer range:(NSRange)range;

3.字符串的比较

最常用的比较相等，返回值为BOOL：

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

以NSComparisonResult作为比较返回结果的方法：

- (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; // locale arg used to be a dictionary pre-Leopard. We now accept NSLocale. Assumes the current locale if non-nil and non-NSLocale. nil continues to mean canonical compare, which doesn't depend on user's locale choice.- (NSComparisonResult)caseInsensitiveCompare:(NSString *)string;- (NSComparisonResult)localizedCompare:(NSString *)string;- (NSComparisonResult)localizedCaseInsensitiveCompare:(NSString *)string;

- (NSComparisonResult)localizedStandardCompare:(NSString *)string NS_AVAILABLE(10_6, 4_0);

返回结果NScomparisonResult解释，

typedef NS_ENUM(NSInteger, NSComparisonResult) {

 NSOrderedAscending = -1L, //1 递增

 NSOrderedSame, //0  相等

 NSOrderedDescending//1 递减

};

参数options：

NSStringCompareOptions说明NSCaseInsensitiveSearch不区分大小写比较NSLiteralSearch区分大小写比较NSBackwardsSearch从字符串末尾开始搜索NSAnchoredSearch搜索限制范围的字符串NSNumericSearch按照字符串里的数字为依据，算出顺序NSDiacriticInsensitiveSearch忽略 "-" 符号的比较NSWidthInsensitiveSearch忽略字符串的长度，比较出结果NSForcedOrderingSearch忽略不区分大小写比较的选项NSRegularExpressionSearch只能应用于 rangeOfString:..., stringByReplacingOccurrencesOfString:...和 replaceOccurrencesOfString:...方法比较原理，如果没有调用option的方法，比较是从两个字符串的第一个字母开始一一对比，相同则比较下一个，不同则返回结果为升序或者降序，两个比较字符串建议长度一致，不一致也可以比较，比如：

@"agc" compare @" ab" //返回降序，

@"abc" compare @"gd" //比较第一个字母之后就返回升序

参数range；

是决定前一个比较对象所需比较的范围。参考如下：

[@"AB" compare:@"ABC" options:0 range:NSMakeRange(0,1)] compares "A" to "ABC", not "A" to "A", and will return NSOrderedAscending

4.字符搜索

 //////////搜索基本////////////1.是否包含前缀(以str开头)- (BOOL)hasPrefix:(NSString *)str;//2.是否包含后缀(以str结尾)- (BOOL)hasSuffix:(NSString *)str;//3.获取公共前缀- (NSString *)commonPrefixWithString:(NSString *)str options:(NSStringCompareOptions)mask;//4.是否包含字符串- (BOOL)containsString:(NSString *)str;//5.本地化是否包含字符串(不区分大小写)- (BOOL)localizedCaseInsensitiveContainsString:(NSString *)str;//6.本地化是否包含字符串(标准)- (BOOL)localizedStandardContainsString:(NSString *)str;//7.本地化搜索字符串范围(标准)- (NSRange)localizedStandardRangeOfString:(NSString *)str;   //////////搜索字符串////////////8.搜索(指定字符串)- (NSRange)rangeOfString:(NSString *)searchString;//9.搜索(指定字符串,条件)- (NSRange)rangeOfString:(NSString *)searchString options:(NSStringCompareOptions)mask;//10.搜索(指定字符串,条件,范围)- (NSRange)rangeOfString:(NSString *)searchString options:(NSStringCompareOptions)mask range:(NSRange)searchRange;//11.搜索(指定字符串,条件,范围,本地化)- (NSRange)rangeOfString:(NSString *)searchString options:(NSStringCompareOptions)mask range:(NSRange)searchRange locale:(nullable NSLocale *)locale;   //////////搜索字符集合////////////12.搜索(指定字符集合)- (NSRange)rangeOfCharacterFromSet:(NSCharacterSet *)searchSet;//13.搜索(指定字符集合,条件)- (NSRange)rangeOfCharacterFromSet:(NSCharacterSet *)searchSet options:(NSStringCompareOptions)mask;//14.搜索(指定字符集合,条件,范围)- (NSRange)rangeOfCharacterFromSet:(NSCharacterSet *)searchSet options:(NSStringCompareOptions)mask range:(NSRange)searchRange;//15.用字符串的字符编码指定索引查找位置- (NSRange)rangeOfComposedCharacterSequenceAtIndex:(NSUInteger)index;//16.用字符串的字符编码指定区域段查找位置- (NSRange)rangeOfComposedCharacterSequencesForRange:(NSRange)range;

字符串搜索主要是检测对象是否有前缀，后缀，子字符串等作用。

对于操作路径和扩展名有极大帮助【传送门】

5.字符串拼接

- (NSString *)stringByAppendingString:(NSString *)aString;- (NSString *)stringByAppendingFormat:(NSString *)format, ... NS_FORMAT_FUNCTION(1,2);

如果是添加路径的话可以使用：

- (NSString *)stringByAppendingPathComponent:(NSString *)str;

6.字符串转化为基本数据

@property (readonly) double doubleValue;@property (readonly) float floatValue;@property (readonly) int intValue;@property (readonly) NSInteger integerValue NS_AVAILABLE(10_5, 2_0);@property (readonly) long long longLongValue NS_AVAILABLE(10_5, 2_0);@property (readonly) BOOL boolValue NS_AVAILABLE(10_5, 2_0);

注意：这里需要提示一下，如果字符串内全是数字，则会全部转化（如果有小数点，转为float和double类型会全转，其他形式只取整数，），如果全是非数字，或者没有以数字开头，怎转化值为0，比如：@"dgtgwge566" //0 如果开头以数字开头，开始会提取到开头几个数字的，后面的提取不了，如：@"456dkhgeo90" //456

7.字符大小写转化

  //////////字符串大小写转换//////////    NSString *string = @"string";    NSLog(@"大写:         %@", string.uppercaseString);    NSLog(@"小写:         %@", string.lowercaseString);    NSLog(@"首字母大写:    %@", string.capitalizedString);    //输出:   大写:         STRING    //输出:   小写:         string    //输出:   首字母大写:    String//本地化(大写)- (NSString *)uppercaseStringWithLocale:(nullable NSLocale *)locale; //本地化(小写)- (NSString *)lowercaseStringWithLocale:(nullable NSLocale *)locale;//本地化(首字母大写)- (NSString *)capitalizedStringWithLocale:(nullable NSLocale *)locale;

8.字符串分行分段

   //////////分行////////////1.指定范围,分行取字符串- (void)getLineStart:(nullable NSUInteger *)startPtr end:(nullable NSUInteger *)lineEndPtr contentsEnd:(nullable NSUInteger *)contentsEndPtr forRange:(NSRange)range;//2.获取指定范围该行的范围- (NSRange)lineRangeForRange:(NSRange)range;   //////////分段////////////3.指定范围,分段取字符串- (void)getParagraphStart:(nullable NSUInteger *)startPtr end:(nullable NSUInteger *)parEndPtr contentsEnd:(nullable NSUInteger *)contentsEndPtr forRange:(NSRange)range;//4.获取指定范围该段落的范围- (NSRange)paragraphRangeForRange:(NSRange)range;  //////////字符串分行,分段//////////    NSString *string = @"123 456\nABC,DEF\nabc.def";    //获取该行的范围(指定范围)    NSRange range1 = [string lineRangeForRange:NSMakeRange(0, 10)];    NSLog(@"%ld 行长度:     %ld", range1.location, range1.length);    //输出:       0 行长度:     16    //获取该段落范围(指定范围)    NSRange range2 = [string paragraphRangeForRange:NSMakeRange(0, 3)];    NSLog(@"%ld 段落长度:   %ld", range2.location, range2.length);    //输出:       0 段落长度:   8

9.字符串列举条件

NSStringEnumerationOptions说明NSStringEnumerationByLines按行NSStringEnumerationByParagraphs按段落NSStringEnumerationByComposedCharacterSequences按字符顺序NSStringEnumerationByWords按单词,字NSStringEnumerationBySentences按句子NSStringEnumerationReverse反向遍历NSStringEnumerationSubstringNotRequired不需要子字符串NSStringEnumerationLocalized本地化

//////////字符串列举//////////       NSString *string = @"123456\nABCDEF\nabcdef    //1.列举(按行)   [string enumerateLinesUsingBlock:^(NSString * _Nonnull line, BOOL * _Nonnull stop) {       NSLog(@"每行:   %@", line);   }];    //输出:    每行:   123456    //输出:    每行:   ABCDEF    //输出:    每行:   abcdef    //2.列举(范围,条件)    [string enumerateSubstringsInRange:NSMakeRange(5, 10) options:NSStringEnumerationByLines usingBlock:^(NSString * _Nullable substring, NSRange substringRange, NSRange enclosingRange, BOOL * _Nonnull stop) {        NSLog(@"%@", substring);        NSLog(@"%ld   %ld", substringRange.location, substringRange.length);        NSLog(@"%ld   %ld", enclosingRange.location, enclosingRange.length);    }];

10字符串编码与转换

//1.选择编码,是否允许有损编码【重要】- (nullable NSData *)dataUsingEncoding:(NSStringEncoding)encoding allowLossyConversion:(BOOL)lossy;//2.选择编码- (nullable NSData *)dataUsingEncoding:(NSStringEncoding)encoding;//3.判断是否可以无损编码- (BOOL)canBeConvertedToEncoding:(NSStringEncoding)encoding;//4.C字符编码转换- (nullable __strong const char *)cStringUsingEncoding:(NSStringEncoding)encoding;//5.判读C字符转化是否可以成功- (BOOL)getCString:(char *)buffer maxLength:(NSUInteger)maxBufferCount encoding:(NSStringEncoding)encoding;//6.指定缓存区转换- (BOOL)getBytes:(nullable void *)buffer maxLength:(NSUInteger)maxBufferCount usedLength:(nullable NSUInteger *)usedBufferCount encoding:(NSStringEncoding)encoding options:(NSStringEncodingConversionOptions)options range:(NSRange)range remainingRange:(nullable NSRangePointer)leftover;//7.对字符串进行编码时所需的最大字节数- (NSUInteger)maximumLengthOfBytesUsingEncoding:(NSStringEncoding)enc;//8.对字符串进行编码时所需的字节数- (NSUInteger)lengthOfBytesUsingEncoding:(NSStringEncoding)enc;//9.可用字符串编码+ (const NSStringEncoding *)availableStringEncodings; //10.本地化编码名称+ (NSString *)localizedNameOfStringEncoding:(NSStringEncoding)encoding;//11.默认C字符串编码+ (NSStringEncoding)defaultCStringEncoding;

11.字符串分割

NSCharacterSet集合

NSCharacterSet说明controlCharacterSet控制符whitespaceCharacterSet空格符whitespaceAndNewlineCharacterSet空格换行符decimalDigitCharacterSet小数letterCharacterSet文字lowercaseLetterCharacterSet小写字母uppercaseLetterCharacterSet大写字母nonBaseCharacterSet非基础alphanumericCharacterSet数字字母decomposableCharacterSet可分解illegalCharacterSet非法punctuationCharacterSet标点capitalizedLetterCharacterSet大写symbolCharacterSet符号newlineCharacterSet换行符

 //////////字符串分割//////////    NSString *string = @"A_B_c_D_E_F";    //分割(指定字符串)    NSArray *resultArr1 = [string componentsSeparatedByString:@"_"];    NSLog(@"%@", resultArr1);    //输出:   (A, B, c, D, E, F)    //分割(指定字符集合)    NSArray *resultArr2 = [string componentsSeparatedByCharactersInSet:[NSCharacterSet lowercaseLetterCharacterSet]];    NSLog(@"%@", resultArr2);        //输出:   ("A_B_" , "_D_E_F")

12.字符串操作（修剪，替换，折叠，填充）

 NSString *string = @"3EWRs a;af";    //////////修剪//////////    NSString *result1 = [string stringByTrimmingCharactersInSet:[NSCharacterSet lowercaseLetterCharacterSet]];    NSLog(@"%@", result1);    //输出:   3EWRs a;    //////////填充//////////    NSString *result2 = [string stringByPaddingToLength:20 withString:@"填充" startingAtIndex:1];    NSLog(@"%@", result2);    //输出:   3EWRs a;af充填充填充填充填充填    //////////折叠//////////    NSString *result3 = [string stringByFoldingWithOptions:NSNumericSearch locale:[NSLocale systemLocale]];    NSLog(@"%@", result3);    //输出:   3EWRs a;af    //////////替换//////////    //替换(指定字符串)    NSString *result4 = [string stringByReplacingOccurrencesOfString:@" " withString:@"替换"];    NSLog(@"%@", result4);    //输出:   3EWRs替换a;af    //替换(指定字符串,条件,范围)    NSString *result5 = [string stringByReplacingOccurrencesOfString:@"a" withString:@"替换" options:NSRegularExpressionSearch range:NSMakeRange(0, string.length - 2)];    NSLog(@"%@", result5);    //输出:   3EWRs 替换;af    //替换(指定范围)    NSString *result6 = [string stringByReplacingCharactersInRange:NSMakeRange(0, string.length) withString:@"替换"];    NSLog(@"%@", result6);    //输出:   替换

13.字符串写入

//////////字符串写入//////////    //写入到指定路径,编码的文件中    [string writeToFile:@"/Users/Desktop/LuisX.txt" atomically:YES encoding:NSUTF8StringEncoding error:nil];    //写入到指定URL,编码的文件中    [string writeToURL:[NSURL URLWithString:@"file://LuisX.text"] atomically:YES encoding:NSUTF8StringEncoding error:nil];

14NSMutableString的介绍

NSMutableString是NSString的字类，可以动态的扩展字符串。

初始化也可以分配容量

 //////////字符串分配容量//////////   //1.初始化容量为Capacity大小的字符串  (需要手动释放内存)   NSMutableString *mutableStr1 = [[NSMutableString alloc] initWithCapacity:20];   //2.初始化容量为Capacity大小的字符串  (不需要手动释放内存)   NSMutableString *mutableStr2 = [NSMutableString stringWithCapacity:20];

扩展方法

 NSMutableString *str = [NSMutableString stringWithString:@"string"];    //////////插入//////////    [str insertString:@"123" atIndex:2];    NSLog(@"%@", str);    //输出:   st123ring    //////////删除//////////    [str deleteCharactersInRange:NSMakeRange(2, 2)];    NSLog(@"%@", str);    //输出:   st3ring    //////////拼接//////////    [str appendString:@"456"];    NSLog(@"%@", str);    //输出:   st3ring456    //////////格式化拼接//////////    [str appendFormat:@"7 89"];    NSLog(@"%@", str);    //输出:   st3ring4567 89    //////////设置新字符串//////////    [str setString:@"string"];    NSLog(@"%@", str);    //输出:   string    //////////字符串替换//////////    //1.指定范围替换    [str1 replaceCharactersInRange:NSMakeRange(2, 2) withString:@"123"];    NSLog(@"%@", str1);    //输出:   st123ng    //2.指定字符串,条件,范围替换    [str1 replaceOccurrencesOfString:@"123" withString:@"--" options:NSRegularExpressionSearch range:NSMakeRange(0, str1.length)];    NSLog(@"%@", str1);    //输出:   st--ng

本文转自：http://www.jianshu.com/p/d3f343b71cc2

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