C++类依赖项

Question

我的班级遇到了一些问题,因为它们彼此依赖,如果没有宣布另一个,就不能宣布.

class block: GtkEventBox {

    public:
        block(board board,guint x,guint y): image("block.png") {
            this.board = board;
            this.x = x;
            this.y = y;
            board.attach(this,x,y,x+1,y+1);
        }
        void move(guint x,guint y) {
            board.remove(this);
            this.x = x;
            this.y = y;
            board.attach(this,x,y,x+1,y+1);
        }

    private:
        guint x, y;
        board board;
        GtkImage image;

};

class board: Gtk::Table {

    public:
        board(): Gtk::Table(25,20) {
            blocks_c = 0;
        }
        void addBlock(guint x,guint y) {
            blocks_a[blocks_c++] = new block(this,x,y);
        }

    private:
        block* blocks_a[24];
        int blocks_c;

};

正如您所看到的,"块"类需要知道"板"是什么,反之亦然.提前致谢!

Answer 1

在"阻止"之前定义"board"并向前声明"block"类.此外,将板函数的实现移出类定义.

// forward declare block class
class block;

// declare board class
class board: Gtk::Table {

    public:
        board();
        void addBlock(guint x,guint y);

    private:
        block* blocks_a[24];
        int blocks_c;

};

// declare block class
class block: GtkEventBox {

    public:
        block(board board,guint x,guint y);
        void move(guint x,guint y);

    private:
        guint x, y;
        board board;
        GtkImage image;

};

// define member functions (implementation) here...

Answer 2

1. 使用此行向前声明您的block班级board:

   类块;

2. 在两个类的声明之后放置函数体的代码.向前声明您的类并不能使其所有函数可用,它只是允许编译器知道这样的类存在.它只允许使用指向这样一个类的指针(因为指针类型的大小不依赖于类的布局).