OC基础：NSString

任何一个优秀的标准库都需要一个优秀的字符串类，带有Foundation的Objective_C也不例外。实际上Foundation框架中有一个优秀的字符串类--NSString。

NSString的用法总结如下：

1.NSString字符串的创建方法

#pragma mark - 初始化字符串
-(void)CreatingAndInitializingStrings
{
    //空字符串
    NSString *string = [NSString string];
    string = [[NSString alloc]init];
    string = @"";
    
    //通过字符串生成字符串
    string = [NSString stringWithString:string];
    string = [[NSString alloc]initWithString:string];
    string = string;
    
    // 组合生成NSString
    string = [NSString stringWithFormat:@"Hello, %@",@"World"];
    string = [[NSString alloc]initWithFormat:@"Hello, %@",@"World"];
    
    // 通过utf-8字符串
    string = [NSString stringWithUTF8String:string.UTF8String];
    string = [[NSString alloc]initWithUTF8String:string.UTF8String];
    
    //通过C字符串
    const char *cStr = "Hello,world";
    //const char *cStr = [string cStringUsingEncoding:NSUTF8StringEncoding];
    string = [NSString stringWithCString:cStr encoding:NSUTF8StringEncoding];
    string = [[NSString alloc]initWithCString:cStr encoding:NSUTF8StringEncoding];

    NSLog(@"CODE:%@",string);
}

2.通过NSString路径读取文件内容

#pragma mark 测试数据
- (NSString *)testData {
    
    // 获取应用中Document文件夹
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    
    // 测试数据
    NSString *string = @"Hello,World;909011853";
    NSString *filePath = [documentsDirectory stringByAppendingPathComponent:@"test.plist"];
    NSError *error;
    [string writeToFile:filePath atomically:YES encoding:NSUTF8StringEncoding error:&error];
    if (error) {
        NSLog(@"错误：%@", error.localizedDescription);
    }
    return filePath;
}

#pragma mark - 通过NSString路径读取文件内容
-(void)CreateAndInitializingFromFile
{
    NSString *filePath = [self testData];
    NSError *error;
    
    // 指定编码格式读取
    NSString *string = [NSString stringWithContentsOfFile:filePath encoding:NSUTF8StringEncoding error:&error];
    string = [[NSString alloc]initWithContentsOfFile:filePath encoding:NSUTF8StringEncoding error:&error];
    
    // 自动打开，并返回解析的编码模式
    NSStringEncoding enc;
    string = [NSString stringWithContentsOfFile:filePath usedEncoding:&enc error:&error];
    
    string = [[NSString alloc] initWithContentsOfFile:filePath usedEncoding:&enc error:&error];
    
    if (error) {
        NSLog(@"错误：%@", error.localizedDescription);
    }
    
    NSLog(@"FILE:%@",string);
}

3.通过NSURL路径读取文件内容

#pragma mark 通过NSURL路径读取文件内容
-(void)CreateAndInitializingFromURL
{
    NSString *filePath = [self testData];
    NSURL *fileUrl = [NSURL fileURLWithPath:filePath];
    NSError *error;
    
    // 指定编码格式读取
    NSString *string = [NSString stringWithContentsOfURL:fileUrl encoding:NSUTF8StringEncoding error:&error];
    string = [[NSString alloc] initWithContentsOfURL:fileUrl encoding:NSUTF8StringEncoding error:&error];
    
    // 自动打开，并返回解析的编码模式
    NSStringEncoding enc;
    string = [NSString stringWithContentsOfURL:fileUrl usedEncoding:&enc error:&error];
    string = [[NSString alloc] initWithContentsOfURL:fileUrl usedEncoding:&enc error:&error];
    
    if (error) {
        NSLog(@"错误：%@", error.localizedDescription);
    }
    
    NSLog(@"URL:%@",string);

}

4.通过NSString或NSURL路径写入NSString

#pragma mark 通过NSString或NSURL路径写入NSString
-(void)WritingFileOrURL
{
    NSString *filePath = [self testData];
    NSURL *fileURL = [NSURL fileURLWithPath:filePath];
    NSError *error;
    NSString *string = @"123123FY";
    
    BOOL write = [string writeToFile:filePath atomically:YES encoding:NSUTF8StringEncoding error:&error];
    
    write = [string writeToURL:fileURL atomically:YES encoding:NSUTF8StringEncoding error:&error];
    
    if (error) {
        NSLog(@"错误：%@", error.localizedDescription);
    }else
    {
        string = [NSString stringWithContentsOfFile:filePath encoding:NSUTF8StringEncoding error:&error];
        NSLog(@"WRITE:%@",string);
    }
}

5.获取字符串长度

-(void)GettingLength
{
    NSString *string = @"Hello,World";
    
    //长度
    NSInteger length = string.length;
     NSLog(@"LENGTH0:%ld",length);
    
    // 指定编码格式后的长度
    length = [string lengthOfBytesUsingEncoding:NSUTF8StringEncoding];
     NSLog(@"LENGTH1:%ld",length);
    
    // 返回存储时需要指定的长度
    length  = [string maximumLengthOfBytesUsingEncoding:NSUTF8StringEncoding];
    NSLog(@"LENGTH2:%ld",length);
}

6.获取Characters和Bytes

-(void)GettingCharactersAndBytes
{
    NSString *string = @"Hello,World,Thank U For your like";
    
    // 提取指定位置的character
    unichar uch = [string characterAtIndex:3];
    NSLog(@"%c",uch);
    
    // 提取Bytes，并返回使用的长度
    NSUInteger length = [string maximumLengthOfBytesUsingEncoding:NSUTF8StringEncoding];
    const void *bytes;
    NSRange range = {0,5};
    BOOL gByte = [string getBytes:&bytes maxLength:length usedLength:&length encoding:NSUTF8StringEncoding options:NSStringEncodingConversionAllowLossy range:range remainingRange:nil];
    if(gByte)
    {
        NSLog(@"length:%lu",(unsigned long)length);
    }
    
}

7.获取C字符串

-(void)GettingCString
{
    NSString *string = @"Hello,World,Thank U For your like";
    
    // 指定编码格式,获取C字符串
    const char *c = [string cStringUsingEncoding:NSUTF8StringEncoding];
    NSLog(@"%s", c);
    
    // 获取通过UTF-8转码的字符串
    const char *UTF8String = [string UTF8String];
    NSLog(@"%s", UTF8String);  
}

8.增加字符串生成新的字符串

#pragma mark - 增加字符串
-(void)CombiningString
{
    NSString *string = @"Hello,World";
    
    // string后增加字符串并生成一个新的字符串
    string = [string stringByAppendingString:@"IOS"];
    
    // string后增加组合字符串并生成一个新的字符串
    string = [string stringByAppendingFormat:@"%@",@";hahah"];
    
    // string后增加循环字符串，stringByPaddingToLength：完毕后截取的长度；startingAtIndex：从增加的字符串第几位开始循环增加。
    string = [string stringByPaddingToLength:30 withString:@";YoYoYo" startingAtIndex:4];
    
    NSLog(@"APPEND:%@",string);

}

9.字符串分割

-(void)DividingString
{
    NSString *string = @"Hello,World;Hello,iOS;Hello,Objective-C";
    
    // 根据指定的字符串分割成数组
    NSArray *array = [string componentsSeparatedByString:@";"];
    NSLog(@"%@",array);
    
    // 通过系统自带的分割方式分割字符串
    NSCharacterSet *set = [NSCharacterSet uppercaseLetterCharacterSet];
    array = [string componentsSeparatedByCharactersInSet:set];
    NSLog(@"%@",array);
    
    // 返回指定位置后的字符串
    NSLog(@"%@",[string substringFromIndex:3]);
    
    // 返回指定范围的字符串
    NSRange range = {1,3};
    NSLog(@"%@",[string substringWithRange:range]);
    
    // 返回指定位置前的字符串
    NSLog(@"%@",[string substringToIndex:3]);

}

10.替换字符串

#pragma mark - 替换字符串
-(void)ReplaceSubstrings
{
    NSString *string = @"Hello,World;Hello,iOS;Hello,Objective-C";
    NSRange searchRange = {0, string.length};
    
    //全局替换
    string = [string stringByReplacingOccurrencesOfString:@"Hello" withString:@"Lovee"];
    NSLog(@"%@",string);
    
    // 设置替换的模式，并设置范围
    string = [string stringByReplacingOccurrencesOfString:@"Love" withString:@"XIXI" options:NSCaseInsensitiveSearch range:searchRange];
    NSLog(@"%@",string);
    
    // 将指定范围的字符串替换为指定的字符串
    string = [string stringByReplacingCharactersInRange:searchRange withString:@"1"];
    NSLog(@"%@",string);
    
}

11.识别和比较字符串

-(void)IdentifyingAndComparingStrings
{
    NSString *string = @"Hello,world";
    NSString *compareStr = @"Hello,Apple";
    
    NSRange searchRange = {0, string.length};
    
    //比较大小
    NSComparisonResult result = [string compare:compareStr];
    NSLog(@"%ld",result);
    
    //前缀比较
    if([string hasPrefix:@"Hello"])
    {
        NSLog(@"Prefix:Hello");
    }
    
    // 后缀比较
    if([string hasSuffix:@"hello"])
    {
        NSLog(@"Suffix:hello");
    }
    
    //比较两个字符串是否相同:
    if([string isEqualToString:compareStr])
    {
        NSLog(@"Equal");
    }else
    {
        NSLog(@"UnEquel");
    }
    
    // 通过指定的比较模式，比较字符串
    result = [string compare:compareStr options:NSCaseInsensitiveSearch];
    // 等价
    result = [string caseInsensitiveCompare:compareStr];
    // 添加比较范围
    result = [string compare:compareStr options:NSCaseInsensitiveSearch range:searchRange];
    // 增加比较地域
    result = [string compare:compareStr options:NSCaseInsensitiveSearch range:searchRange locale:nil];
    
    // 本地化字符串，再比较
    result = [string localizedCompare:compareStr];
    result = [string localizedStandardCompare:compareStr];
    
    // NSCaseInsensitiveSearch模式
    result = [string localizedCaseInsensitiveCompare:compareStr];
    
    // hash值
    NSUInteger hash = string.hash;
    NSLog(@"hash:%lu", (unsigned long)hash);
}

12.获得共享的前缀

#pragma mark 获得共享的前缀
-(void)GettingSharedPrefix
{
    NSString *string = @"Hello,World";
    NSString *compareStr = @"Hello,iOS";
    
    // 返回两个字符串相同的前缀
    NSString *prefix = [string commonPrefixWithString:compareStr options:NSCaseInsensitiveSearch];
    NSLog(@"%@",prefix);
    
}

13.大小写变化

#pragma mark - 大小写变化
-(void)ChangingCase
{
    NSString *string = @"Hello,北京;hello,world;";
    NSLocale *locale = [NSLocale currentLocale];
    
    // 单词首字母变大写
    NSString *result = string.capitalizedString;
    NSLog(@"%@",result);
    // 指定系统环境变化
    result =  [string capitalizedStringWithLocale:locale];
    NSLog(@"%@",result);
    
    //全变大写
    result = string.uppercaseString;
    NSLog(@"%@",result);
    result = [string uppercaseStringWithLocale:locale];
    NSLog(@"%@",result);
    
    // 全变小写
    result = string.lowercaseString;
    NSLog(@"%@",result);
    result = [string lowercaseStringWithLocale:locale];
    NSLog(@"%@",result);
}

14.得到数值

-(void)GetNumberValues
{
    NSString *string = @"123";
    
    NSLog(@"doubleValue:%.3f", string.doubleValue);
    NSLog(@"floatValue:%.2f", string.floatValue);
    NSLog(@"intValue:%d", string.intValue);
    NSLog(@"integerValue:%ld", (long)string.integerValue);
    NSLog(@"longLongValue:%lld", string.longLongValue);
    NSLog(@"boolValue:%d", string.boolValue);

}

15.使用路径

#pragma mark - 使用路径
- (void)WorkingWithPaths {
    
    // 获取应用中Document文件夹
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    
    // 路径拆分为数组中的元素
    NSArray *pathComponents = documentsDirectory.pathComponents;
    // 将数组中的元素拼接为路径
    documentsDirectory = [NSString pathWithComponents:pathComponents];
    
    // 加载测试数据
    NSString *string = @"阳君；937447974";
    NSString *filePath = [documentsDirectory stringByAppendingPathComponent:@"test.plist"];
    [string writeToFile:filePath atomically:YES encoding:NSUTF8StringEncoding error:nil];
    filePath = [documentsDirectory stringByAppendingPathComponent:@"test1.plist"];
    [string writeToFile:filePath atomically:YES encoding:NSUTF8StringEncoding error:nil];
    // 寻找文件夹下包含指定扩展名的文件路径
    NSString *outputName;// 相同的前缀
    NSArray *filterTypes = [NSArray arrayWithObjects:@"txt", @"plist", nil];
    NSUInteger matches = [documentsDirectory completePathIntoString:&outputName caseSensitive:YES matchesIntoArray:&pathComponents filterTypes:filterTypes];
    NSLog(@"找到：%lu", (unsigned long)matches);
    
    // 添加路径
    filePath = [documentsDirectory stringByAppendingPathComponent:@"test"];
    // 添加扩展名
    filePath = [filePath stringByAppendingPathExtension:@"plist"];
    
    // 是否绝对路径
    NSLog(@"absolutePath:%d", filePath.absolutePath);
    
    // 最后一个路径名
    NSLog(@"lastPathComponent:%@", filePath.lastPathComponent);
    
    // 扩展名
    NSLog(@"pathExtension:%@", filePath.pathExtension);
    
    // 去掉扩展名
    string = filePath.stringByDeletingPathExtension;
    
    // 去掉最后一个路径
    string = filePath.stringByDeletingLastPathComponent;
    
    // 批量增加路径，并返回生成的路径
    pathComponents = [filePath stringsByAppendingPaths:pathComponents];
    
    // 没啥用
    string = filePath.stringByExpandingTildeInPath;
    string = filePath.stringByResolvingSymlinksInPath;
    string = filePath.stringByStandardizingPath;
    
}

16.使用URL

#pragma mark 使用URL
- (void)WorkingWithURLs {
    
    NSString *path = @"hello/world";
    
    NSCharacterSet *set = [NSCharacterSet controlCharacterSet];
    
    // 转%格式码
    NSString *string = [path stringByAddingPercentEncodingWithAllowedCharacters:set];
    NSLog(@"%@",string);
    
    // 转可见
    string = string.stringByRemovingPercentEncoding;
    NSLog(@"%@",string);
    
}

17.MutableString修改

-(void)Modifying
{
    NSMutableString *mString = [NSMutableString stringWithCapacity:10];
    
    // Format添加
    [mString appendFormat:@"%@",@"Hello,"];
    NSLog(@"%@",mString);
    
    //添加单一字符串
    [mString appendString:@"World"];
    NSLog(@"%@",mString);
    
    // 删除指定范围的字符串
    NSRange range = {0,3};
    [mString deleteCharactersInRange:range];
    NSLog(@"%@",mString);
    
    // 指定位置后插入字符串
    [mString insertString:@"555555" atIndex:0];
    NSLog(@"%@",mString);
    
    // 替换指定范围的字符串
    [mString replaceCharactersInRange:range withString:@"111"];
    NSLog(@"%@",mString);
    
    // 将指定范围内的字符串替换为指定的字符串，并返回替换了几次
    NSUInteger index =  [mString replaceOccurrencesOfString:@"1" withString:@"23" options:NSCaseInsensitiveSearch range:range];
    NSLog(@"replaceOccurrencesOfString:%lu", (unsigned long)index);
    NSLog(@"%@",mString);
    
    // 字符串全替换
    [mString setString:@"xixihaha"];
    NSLog(@"%@",mString);

}

demo地址：demo