How to convert NSData to byte array in iPhone?

You can't declare an array using a variable so Byte byteData[len]; won't work. If you want to copy the data from a pointer, you also need to memcpy (which will go through the data pointed to by the pointer and copy each byte up to a specified length).

Try:

NSData *data = [NSData dataWithContentsOfFile:filePath];NSUInteger len = [data length];Byte *byteData = (Byte*)malloc(len);memcpy(byteData, [data bytes], len);

This code will dynamically allocate the array to the correct size (you must free(byteData) when you're done) and copy the bytes into it.

You could also use getBytes:length: as indicated by others if you want to use a fixed length array. This avoids malloc/free but is less extensible and more prone to buffer overflow issues so I rarely ever use it.

You could also just use the bytes where they are, casting them to the type you need.

unsigned char *bytePtr = (unsigned char *)[data bytes];

Already answered, but to generalize to help other readers:

    //Here:   NSData * fileData;    uint8_t * bytePtr = (uint8_t  * )[fileData bytes];    // Here, For getting individual bytes from fileData, uint8_t is used.    // You may choose any other data type per your need, eg. uint16, int32, char, uchar, ... .    // Make sure, fileData has atleast number of bytes that a single byte chunk would need. eg. for int32, fileData length must be > 4 bytes. Makes sense ?    // Now, if you want to access whole data (fileData) as an array of uint8_t    NSInteger totalData = [fileData length] / sizeof(uint8_t);    for (int i = 0 ; i < totalData; i ++)    {        NSLog(@"data byte chunk : %x", bytePtr[i]);    }