STL Composed Types

Hi all.
First of all let me apologize by my english.
I've googled a lot about my problem, but I had not find anything conclusive.
I have the following piece of code:

Code:

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vector < map < int , char * > > bank;
      bank . reserve ( 10 );
      if ( bank [ 0 ] [ 0 ] == "a" ) //Memory access error (Access violation at address #blabla)

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which give me the error indicated in comment.
So, to test, I included the following line before "if", and the error changes to that line

Code:

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bank [ 0 ] [ 0 ] = "b"; //Same error

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Finally, the following inserted in place of the line above, works.
Code: ( text )

Code:

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      map < int , char * > data;
      data [ 0 ] = "a";
      bank . push_back ( data );

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But this is hardly an option to me. Mainly because I need, most of times, to test the variable "bank" (even the NULL address existence, which tells me that new item insertion is ok) before I can decide what to do. Beside that, that association grows interactively.
As I can see, it seems a problem with map allocation.
So, my exactly question is how can I use this type of association ( vector < map < type1 , type2 > > ) without get into Mermory access violation errors? Is there a way to previously initialize that association in a manner that allow me to insert new element just doing
Code: ( text )

Code:

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bank [ i ] [ j ] = "some"

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even after the limits previously defined (growing the association)?
Please excuse me if this is trivial, but I'm new to STL.
I appreciate any helps.
Thanx in advance.

The reserve() method merely "reserves" memory, but doesn't make it legal to access the reserved elements (the vector's size is still 0). reserve() usually goes hand-in-hand with push_back().

Another thing is that using a char* for strings may not be a good idea. Use the std::string class instead.

OK. I agree, but there is a way to avoid push_back? I've seen many examples of vectors where elements are created just with "bank [i][j]=some;". push_back means a lot of rework to me.

Then use resize() instead of reserve(), or a vector constructor that takes the number of items.

The std::string thing is important, too. You cannot compare char*-strings with ==. Nor is it safe to insert string constants into a char* container. (It's just barely legal, even.)

Code:

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vector < map < int , string > > bank(10);

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Quote:

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Originally Posted by tuxman

OK. I agree, but there is a way to avoid push_back? I've seen many examples of vectors where elements are created just with "bank [i][j]=some;". push_back means a lot of rework to me.

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In a vector elements are never "created" using array syntax, exisitng elements are simply overwritten. You don't have any existing elements, the container size is still zero!

Quote:

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Originally Posted by tuxman

OK. I agree, but there is a way to avoid push_back? I've seen many examples of vectors where elements are created just with "bank [i][j]=some;". push_back means a lot of rework to me.

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If you want elements to be created, use a map<int,map<int,string> >.

Quote:

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Originally Posted by tuxman

push_back means a lot of rework to me.

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It's nothing but a slight syntactical difference. Suck it up! :)