【转】NSString / NSData / char* 类型之间的转换

原文 ：http://www.cnblogs.com/pengyingh/articles/2341880.html

 

NSString 转换成NSData 对象

 

 NSData* xmlData = [@"testdata" dataUsingEncoding:NSUTF8StringEncoding]; 

NSData 转换成NSString对象

 NSData * data; 2 NSString *result = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding]; 

NSData 转换成char*

 NSData *data;

 2 char *test=[data bytes]; 

char* 转换成NSData对象

 

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

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

 

 1. NSString转化为UNICODE String：

 (NSString*)fname ＝ @“Test”; 
char fnameStr[10];
 3 memcpy(fnameStr, [fname cStringUsingEncoding:NSUnicodeStringEncoding], 2*([fname length])); 

与strcpy相比，memcpy并不是遇到''就结束，而是一定会拷贝完n个字节

2. NSString 转化为 char *

 NSString * str＝ @“Test”;
 2 const char * a = [str UTF8String]; 

3.char * 转化为 NSString

NSString *str = [NSString stringWithCString encoding:NSUTF8StringEncoding]; 

4. char * 转化 NSData
 方法一：

1 char * a = (char*)malloc(sizeof(byte)*16); 

NSData *data = [NSData dataWithBytes: a length:strlen(a)]; 


 方法二：

    转换为NSString：  - (id)initWithUTF8String:(const char *)bytes
    然后用NSString的  - (NSData *)dataUsingEncoding:(NSStringEncoding)encoding

5. NSData 转化 char *

  NSData data ；

 2 char* a=[data bytes]; 


6. NSData 转化 NSString;

 NSData* data;

  2 NSString* aStr = ［NSString alloc] initWithData:data encoding:NSASCIIStringEncoding]; 

7. NSString 转化 NSData对象

 NSData* xmlData = [@"testdata" dataUsingEncoding:NSUTF8StringEncoding]; 

NSString 转化 NSURL  

 //NSURL *url = [NSURL URLWithString:[str   stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding ]]; 
NSString *urlString=[@"http://www google.com/search?client=safari&rls=en&q=搜索&ie=UTF-8&oe=UTF-8" stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];

NSURL 转化 NSString

NSURL *url=[NSURL URLWithString:urlString];
NSString *s=[[url absoluteString] stringByReplacingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
NSArray *arr = [urlStr componentsSeparatedByString:@"&"]; 
NSURL *url = [NSURL URLWithString:[[arr objectAtIndex:0] stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding ]]; 
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url]; 
[request setHTTPMethod:@"POST"]; 

NSMutableArray *_array = [[NSMutableArray alloc] initWithCapacity:0]; 
for (int i = 1; i < [arr count]; ++i ){ 
NSString *str = [arr objectAtIndex:i]; 
[_array addObject:str]; 
} 
[_array componentsJoinedByString:@"&"]; 
NSData *data = [[_array componentsJoinedByString:@"&"] dataUsingEncoding: NSASCIIStringEncoding]; 
[request setHTTPBody:data];
 // 发送请求并获得服务器反馈的数据
    NSData *urldata = [AESEnCDeCViewController Get:url];
    
    // 第一种 转换NSData数据到char*字符串
    char * test = (char*)[urldata bytes];
    std::string old = deaes(test);
    
    // 第二种 转换NSData到UTF8编码的NSString中再转换为char*字符串
//    NSString *desStr = [[NSString alloc] initWithData:urldata encoding:NSUTF8StringEncoding];
//    const char *desresult = [desStr UTF8String];
//    std::string old = deaes(desresult);
    
    // 解密字字符串到明文
    NSString *oldstr = [[NSString alloc] initWithCString:old.c_str()];
 

很多时候软件读取的中文网页编码集是gb2312，所以显示出来的是乱码。这时需要将NSString文字编码转换

1 NSURL *url = [NSURL URLWithString:urlStr];
2 NSData *data = [NSData dataWithContentsOfURL:url];    
3 NSStringEncoding enc = CFStringConvertEncodingToNSStringEncoding(kCFStringEncodingGB_18030_2000);    
4 NSString *retStr = [[NSString alloc] initWithData:data encoding:enc];