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digitalmars.D.learn - Object.factory create instance failed?

reply Sam Hu <samhudotsamhu gmail.com> writes:
The Dmd2.030 spec. said:

static Object factory(string classname); 
Create instance of class specified by classname. The class must either have no
constructors or have a default constructor. 

and said also:
class ClassInfo
static ClassInfo find(in char[] classname); 
Search all modules for ClassInfo corresponding to classname. 

Returns:
null if not found 

Object create(); 
Create instance of Object represented by 'this'. 

In below code snippet:

class Dog
{
public void bark(){}
}
int main(string[] args)
{
auto obj=Object.factory("Dog");
Dog doggie=cast(Dog)obj;
doggie.bark;

return 0;
}

Compiled successfully but failed when run:
Object.Error:Access Violation.

I also tried ClassInfo.find(string classname),ClassInfo.create() but caused the
same error.

In the above code snippet,if I wrote as below:
class Dog{...}
int main(string[] args)
{
Object obj=Object.factory("Dog");
obj=new Dog;   //1
Dog doggie=cast(Dog)obj;//2
doggie.bark;

return 0;
}
Everything works fine.But it seems that this does not make sense to dynamic
create class instance.It is just the same as below:
Object obj;
obj=new Dog;
(cast(Dog)obj).bark;

So is there any other options can I reach the goal,i.e.,dynamically create an
class instance and invoke its method?

Thanks in advance.

Regards,
Sam
Jun 25 2009
next sibling parent Sam Hu <samhudotsamhu gmail.com> writes:
Sam Hu Wrote:


 The Dmd2.030 spec. said:
 
 static Object factory(string classname); 
 Create instance of class specified by classname. The class must either have no
constructors or have a default constructor. 
 
 and said also:
 class ClassInfo
 static ClassInfo find(in char[] classname); 
 Search all modules for ClassInfo corresponding to classname. 
 
 Returns:
 null if not found 
 
 Object create(); 
 Create instance of Object represented by 'this'. 
 
 In below code snippet:
 
 class Dog
 {
 public void bark(){}
 }
 int main(string[] args)
 {
 auto obj=Object.factory("Dog");
 Dog doggie=cast(Dog)obj;
 doggie.bark;
 
 return 0;
 }
 
 Compiled successfully but failed when run:
 Object.Error:Access Violation.
 
 I also tried ClassInfo.find(string classname),ClassInfo.create() but caused
the same error.
 
 In the above code snippet,if I wrote as below:
 class Dog{...}
 int main(string[] args)
 {
 Object obj=Object.factory("Dog");
 obj=new Dog;   //1
 Dog doggie=cast(Dog)obj;//2
 doggie.bark;
 
 return 0;
 }
 Everything works fine.But it seems that this does not make sense to dynamic
create class instance.It is just the same as below:
 Object obj;
 obj=new Dog;
 (cast(Dog)obj).bark;
 
 So is there any other options can I reach the goal,i.e.,dynamically create an
class instance and invoke its method?
 
 Thanks in advance.
 
 Regards,
 Sam
 
 


BTW,why __traits has no isStaticFunction?
Thanks in advance.
Jun 25 2009
prev sibling parent reply John C <johnch_atms hotmail.com> writes:
Sam Hu Wrote:


 
 In below code snippet:
 
 class Dog
 {
 public void bark(){}
 }
 int main(string[] args)
 {
 auto obj=Object.factory("Dog");
 Dog doggie=cast(Dog)obj;
 doggie.bark;
 
 return 0;
 }
 
 Compiled successfully but failed when run:
 Object.Error:Access Violation.
 
 I also tried ClassInfo.find(string classname),ClassInfo.create() but caused
the same error.
 


Object.factory requires a fully qualified class name, so if class Dog resides
in module animals, call Object.factory("animals.Dog").
Jun 25 2009
parent reply Sam Hu <samhudotsamhu gmail.com> writes:
John C Wrote:


 Object.factory requires a fully qualified class name, so if class Dog resides
in module animals, call Object.factory("animals.Dog").


It works now.Great!Thanks so much!

But...may I ask how do you know that?(requires full name).I went through the
object.di but nothing relative found.
Jun 25 2009
next sibling parent reply Ary Borenszweig <ary esperanto.org.ar> writes:
Sam Hu escribió:

 John C Wrote:
 

 Object.factory requires a fully qualified class name, so if class Dog resides
in module animals, call Object.factory("animals.Dog").


 
 It works now.Great!Thanks so much!
 
 But...may I ask how do you know that?(requires full name).I went through the
object.di but nothing relative found.


There: http://d.puremagic.com/issues/show_bug.cgi?id=3093
Jun 25 2009
parent Sam Hu <samhudotsamhu gmail.com> writes:
Ary Borenszweig Wrote:


 Sam Hu escribi?

 John C Wrote:
 

 Object.factory requires a fully qualified class name, so if class Dog resides
in module animals, call Object.factory("animals.Dog").


 
 It works now.Great!Thanks so much!
 
 But...may I ask how do you know that?(requires full name).I went through the
object.di but nothing relative found.


 
 There: http://d.puremagic.com/issues/show_bug.cgi?id=3093


Thanks a lot.

I found the reflection(object module + __traits) of the current version of D2
is very powerful already .Wondering how come some ppl here felt that D is still
lack of reflection?
Jun 25 2009
prev sibling parent John C <johnch_atms hotmail.com> writes:
Sam Hu Wrote:


 John C Wrote:
 

 Object.factory requires a fully qualified class name, so if class Dog resides
in module animals, call Object.factory("animals.Dog").


 
 It works now.Great!Thanks so much!
 
 But...may I ask how do you know that?(requires full name).I went through the
object.di but nothing relative found.
 


Common sense, to be honest.
Jun 26 2009