structures, inheritance and definition

Question

Hi, i need to help with structures, inheritance and definition.

//define struct
struct tStruct1{
    int a;
};

//definition
tStruct1 struct1{1};

and inheritance

struct tStruct2:tStruct1{
    int b;
};

How can I define it in declaration line?

tStruct2 struct2{ ????? };

One more question, how can i use inheritance for structures defined with typedef struct?

Answer 1

First off, the typedef for a structure doesn't change anything, it only introduces an alternative name for the type. You can still inherit from it as usual.

The Type identifier{params} syntax for definitions is C++0x syntax for the new uniform initialization. In pre-C++0x you have two choices for initialization of user-defined types.

Aggregate Initialization

Aggregates are POD types and arrays of PODs or built-in types. They can be initialized using initializer lists with curly braces:

struct A {
    int i;
};
struct B {
    A j;
    int k;
};

B b = {{1}, 2 };

This is covered in more detail in this InformIT article.

As noted this only works for POD-types and thus doesn't work when inheritance comes into play. In that case you have to use

User-defined constructors

They allow you to initialize your custom types rather freely by defining special member functions:

struct A {
    int i;
    A(int number) : i(number) {}
};
struct B : A {
    int j;
    B(int number1, number2) : A(number1), j(number2) {}
};

B b(1, 2);

Constructors are covered in more detail in this InformIT article.