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?
使用时注意些什么? 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?
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。 谢谢easypower版主 不太明白:
rex12:
With acdbOpenAcDbEntity() you can open ONLY Objects derived from AcDbEntity,
With acdbOpenAcDbObject() you can open ONLY Objects NOT derived from AcDbEntity(that is, have no graphics).
acdbOpenObject()-> there are more possibilities. All descriptions you will find in docs.
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:
That's not correct. acdbOpenAcDbObject() will open objects that are derived from AcDbEntity - it will open any type of object.
rex12:
well it's may be, I haven't try it, all i have done was to read reference and there that is written.
So the reference is not correct or ...?
Generally, I use acdbOpenObject function to open an object.
Best Regards
Art Cooney:
acdbOpenAcDbEntity() checks to see if the object being opened is of a class directly or indirectly derived from
AcDbEntity and returns an error if it is not.
It also takes a reference to an AcDbEntity* as an argument and sets it to point to the opened entity.
acdbOpenAcDbObject will open any object. It takes a reference to an AcDbObject* as AcDbObject* as an argument and
sets it to point to the opened object.
acdbOpenObject() is template function that is implemented for each class and takes a reference to a pointer to that
class and sets it to point to the opened object. This function uses acdbOpenAcDbObject() to do the actual open operation.
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 AcDbObjectPointer class where T is the class you want to use.
When using this class I do not have to mind about closing the object.
AcDbObjectPointer myLine (id, AcDb::kForRead);
myLine->setStartPoint(...);
...
// Never call myLine->close()
Ultimately the AcDbObjectPointer is calling acdbOpenAcDbObject() and close for you.
有什么不明白？？？
Smart Pointer是很好用的
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