Question

我试图将值从Level类传递给Grid类，并且在grid_w和grid_h中发生访问冲突。我尝试过使用extern，但它说invalid storage class for a class member。我尝试使用Grid a; a.setgrid(5);但它无法传递该值。有人可以向我解释一下吗？

Level.cpp

#include "Level.h"
#include "Grid.h"

USING_NS_CC;

using namespace CocosDenshion;

Grid* layer25;

CCScene* Level::scene()
{
    CCScene *scene = CCScene::create();
    Level *layer = Level::create();

    layer25 = Grid::create();
    layer25->retain();

    scene->addChild(layer);
    scene->addChild(layer25);

    return scene;
}

// on "init" you need to initialize your instance
bool Level::init()
{
    if ( !CCLayer::init() )
    {
        return false;
    }
    else {
        setTouchEnabled(true);
    }

    Grid pass;
    pass.setgrid(5); // send value here, retreive in Grid.h


    return true;
}

Level.h

#ifndef __LEVEL_H__
#define __LEVEL_H__

#include "cocos2d.h"
using namespace cocos2d;


class Grid;

class Level : public cocos2d::CCLayer
{

public:
    virtual bool init();  
    static cocos2d::CCScene* scene();
    CREATE_FUNC(Level);
};

#endif // __HELLOWORLD_SCENE_H__

Grid.cpp

#include "Grid.h"

using namespace CocosDenshion;

USING_NS_CC;

CCLayer* Grid::scene()
{
    CCScene *scene = CCScene::create();

    OnetGrid *layer2 = OnetGrid::create();

    scene->addChild(layer2);

    return layer2;
}

// on "init" you need to initialize your instance
bool Grid::init()
{
    if ( !CCLayer::init() )
    {
        return false;
    }
    else {
        setTouchEnabled(true);
    }

    grid();

    return true;
}

void Grid::grid()
{
    int a = 0;
    int b = 0;

    cakes = CCArray::createWithCapacity(grid_w*grid_h);
    cakes->retain();
    CCSize visibleSize = CCDirector::sharedDirector()->getVisibleSize();
    CCPoint origin = CCDirector::sharedDirector()->getVisibleOrigin();

    if (grid_w == 10 && grid_h == 12) {
        int x = 51.5 * grid_w/2;
        int y = 55 * grid_h/2;
        int random[120];
        int rnd;
        int rnd2;
        srand (time(NULL));
        for (int l = 0; l < 60; l++) {
            rnd = rand()%20 + 1;
            rnd2 = rnd;
            random[l] = rnd;
            random[l+60] = rnd2;
        }
        int l = 0;
        for (int j = 0 ; j < grid_h; j++) {
            for ( int k = 0; k < grid_w; k++) {
                CCLabelTTF* tests = CCLabelTTF::create("Done", "Life is goofy", 60);
                tests->setColor(ccc3(0, 0, 0));
                tests->setPosition(ccp(400, 400));
                this->addChild(tests, 5);
            }
        }
    } else {
        // but being executed in here
        char text[256];
        sprintf (text, "%d, %d", grid_h, grid_w);
        CCLabelTTF* tests_ = CCLabelTTF::create(text, "Life is goofy", 60);
        test_->setColor(ccc3(0, 0, 0));
        test_->setPosition(ccp(400, 400));
        this->addChild(test_, 5);
    }
}

Grid.h

#ifndef _GRID_H_
#define _GRID_H_

#include "cocos2d.h"

USING_NS_CC;
using namespace cocos2d;

class Grid : public CCLayer
{
public:
    int grid_w;
    int grid_h;

    virtual bool init();
    void setgrid(int a) //retreive in here, print in Grid.cpp
    {
        switch (a){
        case 1:
            grid_w = 6;
            grid_h = 6;
            break;
        case 2:
            grid_w = 6;
            grid_h = 9;
            break;
        case 3:
            grid_w = 8;
            grid_h = 9;
            break;
        case 4:
            grid_w = 9;
            grid_h = 10;
            break;
        case 5:
            grid_w = 10;
            grid_h = 12;
            break;
        default:
            grid_w = 10;
            grid_h = 12;
            break;
        }

    }
   int getgrid_w() {
        return grid_w;
    }

    int getgrid_h() {
        return grid_h;
    }

    static cocos2d::CCLayer* scene();
    void grid();

    CREATE_FUNC(Grid);
};

#endif

Answer 1

您已向对象声明了一个名为pass的指针，但尚未为其分配任何内存。指针pass可以包含任何随机值，可能是也可能不是有效地址。从未分配位置访问内存为Undefined behavior。

所以你需要使用new分配内存，如下所示：

Grid* pass = new Grid;

这为免费存储中的对象分配内存，以便您可以访问数据成员。一旦完成，请记得释放记忆。

您还可以将对象存储在连续的内存中，如下所示：

Grid gr_obj;
Grid* pass = &gr_obj;

Answer 2

如果不为指针pass分配内存，它如何工作？

Answer 3

您尚未初始化pass。因此，使用未初始化的指针调用方法是未定义的行为。

您需要以下内容：

pass = new Grid();

Answer 4

我找到了答案。 Level *layer = Level::create();首先调用Level::init()，因此在执行Grid pass; pass.setgrid(5);时，它返回Undefined behavior，因为网格层没有分配任何内存。

我所做的是在创建网格图层后移动Level *layer = Level::create();：

CCScene* Level::scene()
{
    CCScene *scene = CCScene::create();

    layer25 = Grid::create();
    layer25->retain();

    Level *layer = Level::create();
    scene->addChild(layer);
    scene->addChild(layer25);

    return scene;
}

访问违规写入位置以传递值

4 个答案: