How to put initialized structs in a struct? - c++

Question

I have a struct :
typedef struct
{
int nNum;
string str;
}KeyPair;
Then I initialize my struct into something like this:
KeyPair keys[] =
{
{0, "tester"},
{2, "yadah"},
{0, "tester"}
};
And yet, let's say a number of other initializations:
KeyPair keysA[] =
{
{0, "tester"},
{2, "yadah"},
{0, "tester"}
};
KeyPair keysB[] =
{
{0, "testeras"},
{2, "yadahsdf"},
{3, "testerasss"}
};
KeyPair OtherkeysA[] =
{
{1, "tester"},
{2, "yadah"},
{3, "tester"}
};
and like 20 more of 'em.
Now, how do I create another struct and initialize it such that it contains these initiazed KeyPairs?
The reason for this is because I will repetitively call a function whose parameters would come for these structs. And I DO NOT want to do it this way:
pressKeyPairs( keys, sizeof( keys) / sizeof( keys[0] ) );
pressKeyPairs( keysA, sizeof( keysA) / sizeof( keysA[0] ) );
pressKeyPairs( keysB, sizeof( keysB) / sizeof( keysB[0] ) );
pressKeyPairs( OtherkeysA, sizeof( OtherkeysA) / sizeof( OtherkeysA[0] ) );
and so on...
So I would like to just loop through a struct containing these inilialized instantiations of KeyPairs...
OR I would like to put these initialized instances of KeyPairs into a vector and just loop through the vector... How do I do that?

Answer 1

Assuming that you have a fixed number key pairs, you could use a structure member function:
typedef struct KeyPairs {
KeyPair keysA[3];
KeyPair keysB[3];
KeyPair otherKeysA[3];
void init() {
keysA[0].nNum = 0;
keysA[0].str = "tester";
keysA[1].nNum = 2;
keysA[1].str = "yadah";
keysA[2].nNum = 0;
keysA[2].str = "tester";
// and so on for other keys
}
} KeyPairs;
Then use it like so:
KeyPairs pairs;
pairs.init();

Answer 2

How about doing real C++ and using constructors ?
(note that typedefs are implicits for structs in C++)
struct KeyPair
{
int nNum;
string str;
public:
KeyPair() {}
KeyPair(int n, string s) : nNum(n), str(s) {}
};
And then use another struct :
struct TripleKeyPair
{
KeyPair keys[3];
TripleKeyPair()
{
// Your initialisation code goes here
}
};
And finally, I wouldn't advice using names such as :
KeysA, KeysB, KeysC ...
Arrays are exactly for this. Why note use std::vector ?

Answer 3

How about using "null" objects as delimiters in the array? You would have to use constructors though:
struct KeyPair
{
KeyPair() : fIsEmpty(true) {}
KeyPair(int nNum_, const char *szStr) : nNum(nNum_), str(szStr), fIsEmpty(false) {}
int nNum;
string str;
bool fIsEmpty;
};
Then you can initialize it like this:
KeyPair allKeys[] =
{
KeyPair(0, "testeras"),
KeyPair(2, "yadahsdf"),
KeyPair(3, "testerasss"),
KeyPair(),
KeyPair(0, "tester"),
KeyPair(2, "yadah"),
KeyPair(3, "tester"),
KeyPair(1, "moreyadah"),
KeyPair()
};
And the iteration is trivial if you implement a kind of strlen() analog for KeyPair object array.