Accessibility of data member in member function before declaration of data member

问题

Consider this code:

class Test
{
public:

Test() { i = 0;  }

private:

int i;
};

Data member 'i' is used even before it is declared/defined. Should this not be a compilation error ? (It compiled fine!!!)

回答1:

The rule is that member functions defined in the class definition are compiled as if they were defined immediately after the class definition.

回答2:

No it shouldn't, within the context of the class definition, all members, data members or functions have complete visibility.

回答3:

where is the data member used before declaration?

class Test
{
public:

Test() { i = 0;  } // constructor

private:

int i;  //datamemeber
};
main()
{
Test obj; // memory allocated only here
}

the constructor is called after only the obj is created in main. then the memory for i is allocated. and the the constructor is called so there is scope and visibility for i

来源：https://stackoverflow.com/questions/9783473/accessibility-of-data-member-in-member-function-before-declaration-of-data-membe