NSString、NSData、char* 类型之间的转换-备

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];

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];

说法二：

iOS中NSString转换成HEX（十六进制）-NSData转换成int

NSString *str = @"0xff055008";

//先以16为参数告诉strtoul字符串参数表示16进制数字，然后使用0x%X转为数字类型

unsigned long red = strtoul([str UTF8String],0,16);

//strtoul如果传入的字符开头是“0x”,那么第三个参数是0，也是会转为十六进制的,这样写也可以：

unsigned long red = strtoul([@"0x6587" UTF8String],0,0);

NSLog(@"转换完的数字为：%lx",red);

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// 十六进制转换为普通字符串的。 + (NSString *)stringFromHexString:(NSString *)hexString { //    char *myBuffer = (char *)malloc((int)[hexString length] / 2 + 1); bzero(myBuffer, [hexString length] / 2 + 1); for (int i = 0; i < [hexString length] - 1; i += 2) { unsigned int anInt; NSString * hexCharStr = [hexString substringWithRange:NSMakeRange(i, 2)]; NSScanner * scanner = [[[NSScanner alloc] initWithString:hexCharStr] autorelease]; [scanner scanHexInt:&anInt]; myBuffer[i / 2] = (char)anInt; } NSString *unicodeString = [NSString stringWithCString:myBuffer encoding:4]; NSLog(@"------字符串=======%@",unicodeString); return unicodeString;       }    //普通字符串转换为十六进制的。    + (NSString *)hexStringFromString:(NSString *)string{ NSData *myD = [string dataUsingEncoding:NSUTF8StringEncoding]; Byte *bytes = (Byte *)[myD bytes]; //下面是Byte 转换为16进制。 NSString *hexStr=@""; for(int i=0;i<[myD length];i++)    { NSString *newHexStr = [NSString stringWithFormat:@"%x",bytes[i]&0xff];///16进制数    if([newHexStr length]==1)    hexStr = [NSString stringWithFormat:@"%@0%@",hexStr,newHexStr];    else    hexStr = [NSString stringWithFormat:@"%@%@",hexStr,newHexStr]; } return hexStr; }

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//int 转data int i = 1; NSData *data = [NSData dataWithBytes: &i length: sizeof(i)]; //data 转int int i; [data getBytes: &i length: sizeof(i)];