NSString 使用方法总结

在 iOS 开发中 NSString 字符串对象是使用的最多的，总结一下方法

-(void) testNSString{  
      
    int i = 10;  
    NSString *str = [NSString stringWithFormat:@"%d",i];  //字符串格式化  
    NSLog(@"%@",str);  
      
    str = @"sysprogram 2017";  
    NSLog(@"%@",str);  
      
    NSString *strRet = [str substringToIndex:7];//截取掉下标7之后的字符串  
    NSLog(@"%@",strRet);  
      
    strRet = [str substringFromIndex:2];        //截取掉下标2之前的字符串  
    NSLog(@"%@",strRet);  
      
    strRet = [str substringFromIndex:str.length- 2];   //只获取后面的两位字符串  
    NSLog(@"%@",strRet);  
      
    //设置截取字符串的范围，从第二位到第七位  
    NSRange rang = NSMakeRange(2, 7);  
    NSString * strRang = [str substringWithRange:rang];  
    NSLog(@"rang = %@",strRang);  
      
    strRet = [str capitalizedString];  //首字母大写  
    NSLog(@"首字母大写:%@",strRet);  
      
    strRet = [str uppercaseString];   //全部转为大写  
    NSLog(@"全部大写:%@",strRet);  
      
    strRet = [str lowercaseString];   //全部转为小写  
    NSLog(@"全部小写:%@", strRet);  
      
    strRet = [str stringByAppendingString:@"xxx"];   //字符串相加  
    NSLog(@"%@",strRet);  
      
    //查找字符串  
    rang = [str rangeOfString:@"2017"];  
    NSLog(@"查找的字符串 index 为 %lu", (unsigned long)rang.location);  
      
    //将搜索中的字符串替换成为一个新的字符串  
    strRet = [str stringByReplacingCharactersInRange:rang withString:@"1999"];  
    NSLog(@"替换后字符串为%@", strRet);  
      
    //将 2017 字符串替换成 1998  
    strRet = [str stringByReplacingOccurrencesOfString:@"2017" withString:@"1998"];  
    NSLog(@"替换后字符串为%@", strRet);  
      
    //字符串比较区分大小写  
    if ([str isEqualToString:@"sysprogram 2017"]) {  
          
        NSLog(@"字符串完全相等");  
    }  
    //字符串开头比较  
    if([str hasPrefix:@"sys"])  
    {  
        NSLog(@"字符串结尾为 sys");  
    }  
    //字符串结尾比较  
    if([str hasSuffix:@"2017"])  
    {  
        NSLog(@"字符串结尾为 2017");  
    }  
}

-(void) testNSString{

int i = 10;

NSString *str = [NSString stringWithFormat:@"%d",i]; //字符串格式化

NSLog(@"%@",str);

str = @"sysprogram 2017";

NSLog(@"%@",str);

NSString *strRet = [str substringToIndex:7];//截取掉下标7之后的字符串

NSLog(@"%@",strRet);

strRet = [str substringFromIndex:2]; //截取掉下标2之前的字符串

NSLog(@"%@",strRet);

strRet = [str substringFromIndex:str.length- 2]; //只获取后面的两位字符串

NSLog(@"%@",strRet);

//设置截取字符串的范围，从第二位到第七位

NSRange rang = NSMakeRange(2, 7);

NSString * strRang = [str substringWithRange:rang];

NSLog(@"rang = %@",strRang);

strRet = [str capitalizedString]; //首字母大写

NSLog(@"首字母大写:%@",strRet);

strRet = [str uppercaseString]; //全部转为大写

NSLog(@"全部大写:%@",strRet);

strRet = [str lowercaseString]; //全部转为小写

NSLog(@"全部小写:%@", strRet);

strRet = [str stringByAppendingString:@"xxx"]; //字符串相加

NSLog(@"%@",strRet);

//查找字符串

rang = [str rangeOfString:@"2017"];

NSLog(@"查找的字符串 index 为 %lu", (unsigned long)rang.location);

//将搜索中的字符串替换成为一个新的字符串

strRet = [str stringByReplacingCharactersInRange:rang withString:@"1999"];

NSLog(@"替换后字符串为%@", strRet);

//将 2017 字符串替换成 1998

strRet = [str stringByReplacingOccurrencesOfString:@"2017" withString:@"1998"];

NSLog(@"替换后字符串为%@", strRet);

//字符串比较区分大小写

if ([str isEqualToString:@"sysprogram 2017"]) {

NSLog(@"字符串完全相等");

}

//字符串开头比较

if([str hasPrefix:@"sys"])

{

NSLog(@"字符串结尾为 sys");

}

//字符串结尾比较

if([str hasSuffix:@"2017"])

{

NSLog(@"字符串结尾为 2017");

}

与文件目录字符串处理相关函数

    //获取文件所在路径
    NSString *strFile = @"/Users/exchen/test.txt";
    NSString *strPath = [strFile stringByDeletingLastPathComponent];
    NSLog(@"strPath: %@",strPath);
    //strPath2: /Users/exchen
    
    //删除文件的扩展名
    NSString *strPath2 = [strFile stringByDeletingPathExtension];
    NSLog(@"strPath2: %@",strPath2);
    //strPath: /Users/exchen/test
    
    //获取文件的扩展名
    NSString *strExtension = [strFile pathExtension];
    NSLog(@"extension: %@",strExtension);
    //extension: txt
    
    //获取文件名
    NSString *strName = [strFile lastPathComponent];
    NSLog(@"strName %@",strName);
    //strName test.txt
    
    //路径相加
    NSString *strNewFilePath = [strFile stringByAppendingPathComponent:@"test2.txt"];
    NSLog(@"strNewFilePath: %@",strNewFilePath);
    //strNewFilePath: /Users/exchen/test.txt/test2.txt
    
    //获取该路径的所有组成部分
    NSArray *strPaths = [strFile pathComponents];
    NSLog(@"strPaths: %@",strPaths);
    /*strPaths: (
           "/",
           Users,
           exchen,
           "test.txt"
           )
    */

//获取文件所在路径

NSString *strFile = @"/Users/exchen/test.txt";

NSString *strPath = [strFile stringByDeletingLastPathComponent];

NSLog(@"strPath: %@",strPath);

//strPath2: /Users/exchen

//删除文件的扩展名

NSString *strPath2 = [strFile stringByDeletingPathExtension];

NSLog(@"strPath2: %@",strPath2);

//strPath: /Users/exchen/test

//获取文件的扩展名

NSString *strExtension = [strFile pathExtension];

NSLog(@"extension: %@",strExtension);

//extension: txt

//获取文件名

NSString *strName = [strFile lastPathComponent];

NSLog(@"strName %@",strName);

//strName test.txt

//路径相加

NSString *strNewFilePath = [strFile stringByAppendingPathComponent:@"test2.txt"];

NSLog(@"strNewFilePath: %@",strNewFilePath);

//strNewFilePath: /Users/exchen/test.txt/test2.txt

//获取该路径的所有组成部分

NSArray *strPaths = [strFile pathComponents];

NSLog(@"strPaths: %@",strPaths);

/*strPaths: (

"/",

Users,

exchen,

"test.txt"

)

NSString 和 NSData 相互转换

NSData* data = [@"string" dataUsingEncoding:NSUTF8StringEncoding]; 

NSData *data; 
NSString *string = [[NSString alloc] initWithData:data  encoding:NSUTF8StringEncoding];

NSData *data; 
char *test=[data bytes];

byte* tempData = malloc(sizeof(byte)*16); 
NSData *content=[NSData dataWithBytes:tempData length:16];

NSData* data = [@"string" dataUsingEncoding:NSUTF8StringEncoding];

NSData *data;

NSString *string = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];

NSData *data;

char *test=[data bytes];

byte* tempData = malloc(sizeof(byte)*16);

NSData *content=[NSData dataWithBytes:tempData length:16];

还有更多的方法，待续......

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