王咣生 发表于 2004-9-23 22:32:00

请问acdbOpenObject,acdbOpenAcDbObject,acdbOpenAcDbEntity()区别?

AcDbEntity, AcDbObject的区别是什么?


acdbOpenAcDbEntity(), acdbOpenAcDbObject(), acdbOpenObject() Global Function的区别是什么?<BR>使用时注意些什么?

easypower 发表于 2004-9-24 08:01:00

1。AcDbEntity, AcDbObject的区别是什么?


答：AcDbEntity继承自AcDbObject，即除AcDbObject所有的属性和方法之外，还增加有自绘方法（属性也不一定），可以说具有图形特性。


2。acdbOpenAcDbEntity(), acdbOpenAcDbObject(), acdbOpenObject() Global Function的区别是什么?<BR>使用时注意些什么?


答：acdbOpenAcDbEntity专用打开AcDbEntity，acdbOpenAcDbObject专用打开AcDbObject，acdbOpenObject会自动根据你的ObjectId所对应实体类型，调用acdbOpenAcDbEntity或acdbOpenAcDbObject。

王咣生 发表于 2004-9-24 11:12:00

回复

谢谢easypower版主

王咣生 发表于 2004-9-25 00:31:00

回复

不太明白:


                                       rex12:<BR>                                       With acdbOpenAcDbEntity() you can open ONLY Objects derived from AcDbEntity,<BR>                                       With acdbOpenAcDbObject() you can open ONLY Objects NOT derived from AcDbEntity(that is, have no graphics).<BR>                                       acdbOpenObject()-&gt; there are more possibilities. All descriptions you will find in docs.<BR>                                       That is a mention for objects openning. There is no matter if you want to open an AcDb Entity or AcDbObject derived object.


                                       Art Cooney:<BR>                                       That's not correct. acdbOpenAcDbObject() will open objects that are derived from AcDbEntity - it will open any type of object.


                                       rex12:<BR>                                       well it's may be, I haven't try it, all i have done was to read reference and there that is written.<BR>                                       So the reference is not correct or ...?<BR>                                       Generally, I use acdbOpenObject function to open an object.<BR>                                       Best Regards


                                       Art Cooney:<BR>                                       acdbOpenAcDbEntity() checks to see if the object being opened is of a class directly or indirectly derived from <BR>                                       AcDbEntity and returns an error if it is not.<BR>                                       It also takes a reference to an AcDbEntity* as an argument and sets it to point to the opened entity.<BR>                                       acdbOpenAcDbObject will open any object. It takes a reference to an AcDbObject* as AcDbObject* as an argument and <BR>                                       sets it to point to the opened object.<BR>                                       acdbOpenObject() is template function that is implemented for each class and takes a reference to a pointer to that<BR>                                       class and sets it to point to the opened object. This function uses acdbOpenAcDbObject() to do the actual open operation.<BR>

王咣生 发表于 2004-9-25 09:36:00

解决方法

很好的方法:<BR>                                       Cyrille Fauvel:<BR>                                       I think Art replied on the subject, but just as a matter of coding style <BR>                                       I prefer using AcDbObjectPointer&lt;T&gt; class where T is the class you want to use.<BR>                                       When using this class I do not have to mind about closing the object.


                                       AcDbObjectPointer&lt;AcDbLine&gt; myLine (id, AcDb::kForRead);<BR>                                       myLine-&gt;setStartPoint(...);<BR>                                       ...<BR>                                       // Never call myLine-&gt;close()<BR>                                       Ultimately the AcDbObjectPointer&lt;T&gt; is calling acdbOpenAcDbObject() and close for you.<BR>

easypower 发表于 2004-9-25 13:31:00

王咣生发表于2004-9-25 0:31:00static/image/common/back.gif回复：（王咣生）回复不太明白:



                                       rex12:                                       With acdbOpenAcDbEntity() you can open ONLY Objects derived from AcDbEntity,                                       With acdbOpenAcDbObject() you...

有什么不明白？？？<BR>

easypower 发表于 2004-9-25 13:32:00

王咣生发表于2004-9-25 9:36:00static/image/common/back.gif回复：（王咣生）解决方法                                        很好的方法:                                       Cyrille Fauvel:                                       I think Art replied on the subject, but just as a matter of coding style                                        I prefer using ...


<BR>Smart Pointer是很好用的


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