iOS 数据类型转换

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''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 stringWithCStringencoding: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];

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

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