如何将NSData转换为NSString或char？

Question

I have an NSData instance containing <7e0006b5 01012605 06070172 7a>, how can I convert it to an NSString containing @"7e0006b501012605060701727a"?

My test code is:

char c_command[26] = {'7', 'e', '0', '0', 
                      '0', '6', 'b', '5', 
                      '0', '1', '0', '1', 
                      '2', '6', '0', '5', 
                      '0', '6', '0', '7', 
                      '0', '1', '7', '2', 
                      '7', 'a'};
NSMutableData *commandToSend  = [[NSMutableData alloc] init];

for (int i = 0; i < 13; i++) {
    unsigned char data_byte;
    char byte_chars[3] = {'\0','\0','\0'};
    byte_chars[0] = c_command[i * 2];
    byte_chars[1] = c_command[i * 2 + 1];
    data_byte = strtol(byte_chars, NULL, 16);
    [commandToSend appendBytes:&data_byte length:1];
}
NSString *str = [[NSString alloc] initWithData:commandToSend encoding:NSASCIIStringEncoding];
NSLog(@"Test command is :%@ \n command to string is:%@", commandToSend, str);

the output of log is:

Test command is :<7e0006b5 01012605 06070172 7a> command to string is:~

Answer 1

NSString *theString =[[NSString alloc]initWithData:data encoding:NSStringEncodingConversionAllowLossy];
    NSLog(@"%@",theString);
    [theString release];

Answer 2

如果数据是从Internet下载的，则可能要使用：

NSString *str = [[NSString alloc] initWithData:NSData encoding:NSASCIIStringEncoding];

Answer 3

NSString has a number of methods for creating strings from bytes, but you'll need to know how the data is encoded. UTF8 is a popular encoding, and if your data is UTF8 encoded you can:

NSString *someString = [NSString stringWithUTF8String:(const char *)[someData bytes]];

There are other methods as well, such as -initWithCharacters:length: and -initWithBytes:length:encoding: .

Start by looking at the reference page for NSString .

Answer 4

I have found out that sometimes the method -stringWithUTF8String:(const char*) from NSString doesn't work too good in conjunction with NSData or NSMutableData. Let's have something like

const char * cString = [yourNSData bytes];

and

NSString * str = [NSString stringWithUTF8String:(const char*)cString];

Occasionally the str was simply nil because the cString was somehow "malformed" (considering UTF-8 chars).

Thus, I would recommend using

NSString * str = [[NSString alloc] initWithData:[yourNSData bytes] encoding:NSUTF8StringEncoding];

which worked allways perfect in my case.