Structures containing pointers to Structures

[POedBoy]

Hi all,

I have a procedure that 'creates' and returns a pointer to a structure. I've already tested that and it works fine on its own.

However, I'm having problems using this pointer within another structure. This will come back with syntax errors..(extraneous code snipped):

Code: Select all

Structure HTTP_Connection
    
    *next.HTTP_Connection
    *prev.HTTP_Connection
    
    ;............
    
    *NetBank.Bank
    *url.URL
    
    ;............
    
EndStructure

Procedure.l HTTP_Create()
    Protected *hc.HTTP_Connection
    
    *hc = AddElement(HTTP_GlobalList())
    *hc\*url.URL = URL_Create()                                       ;<= syntax error
    *hc\*NetBank.Bank = Bank_Create(#HTTP_NetBankSize);<= syntax error
     
    ;...................
     
    ProcedureReturn *hc
EndProcedure

So what am I doin wrong here? Or is this type of thing just not possible in pure?

Thanks ahead of time.

[Pupil]

Your error is that 'Addelement(MyList())' doesn't return the address to the structure. You should do it like this:

Code: Select all

If AddElement(HTTP_GlobalList())
  *hc = @HTTP_GlobalList()
  ; ... etc
Else
  Debug "Run out of memory?"
EndIf

[POedBoy]

I've converted the above procedure to your method, but I still get the same syntax error...

Code: Select all

Procedure.l HTTP_Create()
    Protected *hc.HTTP_Connection
    
    ;*hc = AddElement(HTTP_GlobalList())
    
    If AddElement(HTTP_GlobalList()) 
        *hc = @HTTP_GlobalList() 
        ; ... etc 
    Else 
        Debug "Run out of memory?" 
    EndIf
    
    ;*hc\*url.URL = URL_Create()
    
    If AddElement(URL_GlobalList()) 
        *hc\*url = @URL_GlobalList();<== syntax error still
        ; ... etc 
    Else 
        Debug "Run out of memory?" 
    EndIf
  
    ProcedureReturn *hc
EndProcedure

I'm not really clear as to why this:

Code: Select all

If AddElement(HTTP_GlobalList()) 
        *hc = @HTTP_GlobalList() 

is different than:

Code: Select all

*hc = AddElement(HTTP_GlobalList())

Either way gives me a valid pointer...

[tinman]

I'm not really clear as to why this:

Code: Select all

If AddElement(HTTP_GlobalList()) 
        *hc = @HTTP_GlobalList() 

is different than:

Code: Select all

*hc = AddElement(HTTP_GlobalList())

Either way gives me a valid pointer...

They're different pointers. This is explained in the linked list manual. One is a pointer to the user data and the other is the (address of the user data - 8).

[Pupil]

Hmm, i didn't read trough your post thouroughly enough, and what i wrote in my first post was what i saw was wrong by just glancing through your code. Now i've experimented a bit and realized that you need to remove the '*' from the structure path or you'll get a syntax error.

Small example:

Code: Select all

Structure a1
  a.l
EndStructure

Structure a2
  *a.a1
  *b.a1
EndStructure

a.a2\a = @b.l
*p.a2 = @a

b = 1
Debug *p\a\a

[POedBoy]

Thanks for the help guys..

[blueznl]

re. pointer naming in structures:

http://www.xs4all.nl/~bluez/datatalk/pu ... structures