Writing structs to eprom

Using Arduino Programming Questions
1

Hi,
I am using Arduino UNO, is it possible to write to EEPROM more complicated structures than only key/value ? For example I would like to write that structure:

MyStruct[][]

struct MyStruct
{
int age
short somedate;
string status;
};

2

arduHenry:
I am using Arduino UNO, is it possible to write to EEPROM more complicated structures than only key/value ?

The EEPROM of an UNO is 1024 bytes in size.
You can write anything into it, which fits in size.

arduHenry:
For example I would like to write that structure:

MyStruct[][]

struct MyStruct
{
int age
short somedate;
string status;
};

Declare some kind of bullshit, then save to EEPROM?
Sorry, that cannot work.

Besides of a missing semicolon after 'age', what the hell is "string"?
Is it a 'struct' or some type of data you declared before?

Did you perhaps mix small and capital letter and wanted to refer to a "String" object? String objects are pointers, you cannot just save a pointer. After restorung a pointer you would just have a pointer and not the contents of the original object. So you better forget about "String" objects.

Or maybe you wanted to declare a string, which is a char-array in the C language and might work like that:

struct MyStruct
{ 
    char name[20];  // provide space for names up to a length of 20
    int age;        
    short somedate;
};

Something like that?
Or what?

3

You can use the avr-gcc functions to read and write the EEPROM, and use a struct for the offset of the items by declaring the struct as EEMEM: EEMEM - #5 by Peter_n - Storage - Arduino Forum

Or use a "anything" library : Gammon Forum : Electronics : Microprocessors : I2C - Two-Wire Peripheral Interface - for Arduino (search that page for "I2C_Anything").

4 
template<class T>
int writeToEEPROM(int address, T& value)
{
  union {
    T type;
    byte b[sizeof(T)];
  } 
  temp;

  temp.type = value;
  for (unsigned int i = 0; i < sizeof(T); i++)
  {
    EEPROM.write(address + i, temp.b[i]);
  }
  return sizeof(T);
}


template<class T>
int readFromEEPROM(int address, T& value)
{
  union {
    T type;
    byte b[sizeof(T)];
  } 
  temp;

  for (unsigned int i = 0; i < sizeof(T); i++)
  {
    temp.b[i] = EEPROM.read(address + i);
  }
  value = temp.type;
  return sizeof(T);
}