Viewing NSData contents in Xcode

Question

I am running Xcode and I would like to dump out a NSData*. The variable in question is buffer. Is there a way to do this through the UI or the GDB debugger?

Answer 1

Unfortunately, none of the suggestions so far solved the problem of actually being able to quickly display the data inside NSData.

I wrote a simple method that works the way I need it to. From the GDB window, I can type in print [Util dumpData:theData] and I will get nice, formatted output.

+(void) dumpData:(NSData *)data
{
    unsigned char* bytes = (unsigned char*) [data bytes];

    for(int i=0;i< [data length];i++)
    {
        NSString* op = [NSString stringWithFormat:@"%d:%X",i,bytes[i],nil];
        NSLog(@"%@", op);
    }
}

NsLog Output

0:24
1:0
2:4
3:0
4:0
5:0

Answer 2

The easiest way for me (during local development only!) is to convert to unused NSString instances. Then the values show right up in the debugger. Once I'm finished, I nuke those lines of code.

From this old thread

NSString* newStr = [[NSString alloc] initWithData:theData encoding:NSUTF8StringEncoding];

Answer 3

For Swift code I'm doing the following:

When my program is stopped in a breakpoint I use the "Add expression" option and enter [UInt8](data) where data is my Data instance:

After that I can see the data contents:

Answer 4

In lldb, the following works to let you examine the contents of NSData objects:

You can get the address of the bytes for use with various debugger commands like this:

p (void *)[buffer bytes]

You see something like this:

(void *) $32 = 0x0b5e11f0

If you know the underlying data is a string, you can do this:

p (char *)[buffer bytes]

and the debugger will output:

(char *) $33 = 0x0b5e11f0 "This is the string in your NSData, for example."

Answer 5

No one has ever correctly answered the question. After 2 years I think it's time for one :)

Assuming you have in your code

NSData* myData;

Then in lldb you type

me read `[myData bytes]` -c`[myData length]`

If the format of the dump is not to your liking you can add '-t ' for example

me read `[myData bytes]` -c`[myData length]` -t int

For more help type

help me read

in lldb

Answer 6

Your data instance is empty.

It wouldn't only display the address otherwise. -[NSData description] includes a printout of the contents of the data. The bytes are grouped in fours and printed in hex with a leading 0 placeholder:

char arr[] = {0x1, 0x2, 0xA, 0x4, 0xF};
NSData * dat = [NSData dataWithBytes:arr length:5];
NSLog(@"%@", dat);

2012-07-17 22:24:48.973 PrintDat[61264:403] <01020a04 0f>

Using po dat at the debugger's command line will give you the same results, including the address:

(NSData *) $1 = 0x00007f98da500180 <01020a04 0f>

The contextual menu route that Anshu suggested also uses the description method.