iOS类型转换

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)encoding5. 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
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];