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 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)enco
```
5
NSData 转化 char *
```
NSData data ；
char* a=[data bytes];
```
6
NSData 转化 NSString;
```
NSData* data;
NSString* aStr= ［NSString alloc] initWithData:dataencoding: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()];
```
8
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];
```