Constructor: Basics¶

Constructors: why? (1)¶

Initialization in C

struct point A;	A remains uninitialized ⟶ random values
struct point A = {1,2};	`A` is initialized with `x = 1` and `y = 2`
struct point A; ... A.x = 1; A.y = 2;	Definition ⟶ uninitialized Only set at some later point ⟶ error prone

Initialization in C++

Programmer has no choice
Whenever programmer thinks about a point object, they have to think about its value
⟶ initialization error excluded from the beginning

point A;	Compiler error: “void constructor for point not defined”
point A(1,2);	Only possibility to create a `point`

Short methods are best defined in the class definition itself ⟶ inline

point.h: inline definition¶

class point
{
public:
    point(int x, int y)
    {
        _x = x;
        _y = y;
    }
    // ...
};

Long methods are best defined in the implementation file

`point.h`: declaration	`point.cpp`: definition
class point { public: point(int x, int y); // ... };	point::point(int x, int y) { _x = x; _y = y; }