不带::的.cpp中的C ++类方法调用

Question

I'm new to progamming in C++. I have a good background with Java but C++ is different on many things and I have a question about one of the regarding .h and .cpp files.

I have the following files for a point object with x and y position:

Point.h

#ifndef POINT_H_
#define POINT_H_

class Point{
Point();
Point(int newX, int newY);

public:
    int getX();
    int getY();
    void setX(int newX);
    void setY(int newY);
    void moveBy(int moveX, int moveY);
    Point reverse();
private:
    int x;
    int y;
};
#endif

Point.cpp

#include "Point.h"

using namespace Point;

Point::Point(int newX, int newY){
    x = newX;
    y = newY;
}
int Point::getX(){
    return x;
}
int Point::getY(){
    return y;
}
void Point::setX(int newX){
    x = newX;
}
void Point::setY(int newY){
    y = newY;
}
void Point::moveBy(int moveX, int moveY){
    x += moveX;
    y += moveY;
}
Point Point::reverse(){
    return Point(y,x);
}

I was wondering if there was a way of avoinding the Point::Point part like with std::cout by using namespace.

Thank you

Answer 1

You aren't required to separate your declaration and definition, and these functions are incredibly trivial. So including them in the class definition may actually allow the compiler to perform numerous additional optimizations.

So you could discard the .cpp entirely and the header becomes:

#ifndef POINT_H_
#define POINT_H_

class Point
{
    int x_ { 0 };
    int y_ { 0 };

public:
    Point() = default;
    Point(int x, int y) : x_(x), y_(y) {}

    int getX() const { return x_; }
    int getY() const { return y_; }
    void setX(int x) { x_ = x; }
    void setY(int y) { y_ = y; }
    void moveBy(int x, int y) { x_ += x, y_ += y; }
    Point reverse() const { return Point(y_, x_); }
};

#endif

But you can't avoid the "Point::" part when defining the members outside of the class declaration.

Answer 2

If you want to avoid typing the " Point:: " in front of the getX , getY etc., then the answer is "no" , unfortunately. In C++ and the name of any class (like " Point ") is not a namespace , it's a scope .

What you can only do is inlining the method, defining into the class declaration.

class Point {
  public:
    void a_method() {
      // all the code here!
    }
};

Answer 3

You can't avoid "the Point::Point part," unless you declare the construction inline in the class declaration. The first "Point" defines the scope of the function, and the second "Point" is the name of the constructor function.

However, you could define the constructor(s) inline, like so:

class Point
{
  Point()
  {
    x = 0;
    y = 0;
  }
  Point(int newX, int newY);
  {
    x = newX;
    y = newY;
  }
  // ...
};

Or:

class Point
{
  Point() : x(0), y(0) {}
  Point(int newX, int newY) : x(newX), y(newY) {}
  // ...
};

Or:

class Point
{
  Point(int newX = 0, int newY = 0) : x(newX), y(newY) {}
  // ...
};