NSString / NSData / char 类型之间的转换

1. NSString转化为UNICODE String：

(NSString*)fname ＝ @“Test”;

char fnameStr[10];

memcpy(fnameStr, [fname cStringUsingEncoding:NSUnicodeStringEncoding], 2*([fname length]));

与strcpy相比，memcpy并不是遇到'\0'就结束，而是一定会拷贝完n个字节

2. NSString转化为 char *

NSString * str＝ @“Test”;

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：

   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 ；

  char* a=[data bytes];

6. NSData转化 NSString;

NSData* data;

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

7. NSString转化 NSData对象

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

http://blog.sina.com.cn/s/articlelist_1256141290_14_1.html

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];