NSString / NSData / char* 類型之間的轉換

轉自：http://www.cnblogs.com/pengyingh/articles/2341880.html

1. NSString轉化為UNICODE String：
(NSString*)fname ＝ @“Test”;
char fnameStr[10];
memcpy(fnameStr, [fname cStringUsingEncoding:NSUnicodeStringEncoding], 2*([fname length]));

與strcpy相比，memcpy並不是遇到'\0'就結束，而是一定會拷貝完n個字節

2. NSString 轉化為 char *
NSString * str＝ @“Test”;
const char * a =[str UTF8String];

3.char * 轉化為 NSString

NSString *str=[NSString stringWithCString  encoding:NSUTF8StringEncoding];

4. char * 轉化 NSData
 方法一：
   char * a = (char*)malloc(sizeof(byte)*16);
   NSData *data = [NSData dataWithBytes: a   length:strlen(a)];
 方法二：
   轉換為NSString： - (id)initWithUTF8String:(const char *)bytes
   然后用NSString的 - (NSData *)dataUsingEncoding:(NSStringEncoding)encoding

5. NSData 轉化 char *
  NSData data ；
  char* a=[data bytes];

6. NSData 轉化 NSString;

NSData* data;

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

7. NSString 轉化 NSData對象

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

NSString 轉化 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 轉化 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];
// 發送請求並獲得服務器反饋的數據
    NSData *urldata = [AESEnCDeCViewController Get:url];
    
// 第一種 轉換NSData數據到char*字符串
    char * test = (char*)[urldata bytes];
    std::string old = deaes(test);
    
// 第二種 轉換NSData到UTF8編碼的NSString中再轉換為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()];

 

很多時候軟件讀取的中文網頁編碼集是gb2312，所以顯示出來的是亂碼。這時需要將NSString文字編碼轉換

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