CAD二次开发学习笔记三(封装添加实体到数据库函数)

学会查看ObjectARX帮助文档。
AcGe开头图形计算。
AcDb图形数据库。
在acrxEntryPoint.cpp添加如下代码：

//将实体添加到数据库
//cad中的实体最终都要添加到数据库中才能被显示(图纸其实是一个数据库格式的)，所以它的作用就是添加实体到数据库中
static Acad::ErrorStatus AddToDb(AcDbEntity* ent, AcDbObjectId& objId)
{    
    Acad::ErrorStatus      es;
    AcDbBlockTable*        pBlockTable;
    AcDbBlockTableRecord*  pSpaceRecord;

    if ((es = acdbHostApplicationServices()->workingDatabase()->getBlockTable(pBlockTable, AcDb::kForRead))
        != Acad::eOk) {
            return es;
    }

    if ((es = pBlockTable->getAt(ACDB_MODEL_SPACE, 
        pSpaceRecord,
        AcDb::kForWrite)) != Acad::eOk) {
            return es;
    }


    if ((es = pBlockTable->close()) != Acad::eOk) {
        return es;
    }
    if ((es = pSpaceRecord->appendAcDbEntity(objId, ent)) != Acad::eOk) {
        return es;
    }

    return pSpaceRecord->close();

}
public:

    // - ArxProject2.cmd3 command (do not rename)
    static void ArxProject2cmd3(void)
    {
        // Add your code for command ArxProject2.cmd3 here
        AcGePoint3d ptStart(0,0,0);
        AcDbCircle *pCircle=new AcDbCircle();
        pCircle->setCenter(ptStart);
        pCircle->setRadius(1000);
        //也可以这样定义圆
        //AcDbCircle *pCircle=new AcDbCircle(ptStart,AcGeVector3d(0,0,1),100);
        AcDbObjectId circleId;
        //调用画实体函数
        if(AddToDb(pCircle,circleId)!=Acad::eOk)//传入指针，传出id
            AfxMessageBox( _T("加入实体到数据库失败！"));
        pCircle->close();
    }