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];