FiveTech Software tech support forums

method activate(cAccnFrom, cAccnTo, dFrom, dCOD, oDbCgl, lPrintable) class XBrwGL
  local oldarea := select(), dTo, cStr, a_
  local oDlg, oBrw, oFntTitl, oMFont1, oImg, bInit, oSay, oBtnCgl, nWidth, lTaxCodeAlreadyOpened, cTAccn
  local aDbfs := {                   ;
                   {"oDbHgl", "hgl", "hgl2"}, ;
                   {"oDbSaleman" , "saleman" , "saleman1"}, ;
                   {"oDbJnlhis"  , "jnlhis", "jnlhis2"}  ;
                 }

  cursorWait()
  if !OpenODbfs(aDbfs,,self)
     select (oldarea)
     return nil
  endif
//------------------------------------------------------------------------------------
function OpenODbfs(a_, lExcl, o)
  /* open dbf with unique alias
     a_ must be in the format { {<oDb name>, <dbf name>, <ntx1>, <ntx2>,..., <ntxn>} }
  */

  local lRet := .t., i, nlen := len(a_), j
  local aOpened := {}, oldarea := select()

  default lExcl := .f.


  for i := 1 to nLen
      if net_use(a_[i,2], lExcl,, cGetNewAlias( 'TDF' ))
         aadd(aOpened, select())
         if len(a_[i]) > 2
            for j := 3 to len(a_[i])
                ordListAdd(a_[i,j])
            next
            set order to 1
         endif
         o:&(a_[i,1]) := TDataBase():new()
         o:&(a_[i,1]):cFile := a_[i,2]
         o:&(a_[i,1]):setBuffer(.f.)
      else
         lRet := .f.
         exit
      endif
  next
  // fail? then close those opened so far
  if !lRet
     aeval(aOpened, {|x| (x)->(dbCloseArea())})
  endif
  select (oldarea)
return lRet
 

o:&(a_[i,1]) := TDataBase():new()
o:&(a_[i,1]):cFile := a_[i,2]

o:&(a_[i,1]) := TDataBase():new(,a_[i,2])

  for i := 1 to nLen
      cAlias := cGetNewAlias( 'TDF' )
      if net_use(a_[i,2], lExcl,, cAlias)
         ...
         o:&(a_[i,1]) := TDataBase():new(cAlias, a_[i,2])
         ...
      endif
  next
 

James Bott wrote: It appears that you are opening all the files at once, and setting your own aliases.

With database objects, unique aliases are automatically generated so you don't even need to think about them. You can open multiple copies of the same database and thus not have to worry about saving and restoring the database state (recno, filters, scopes, index, etc.). So you can do things like lookup a customer in a function by opening a copy of the customer file in that function and closing it at the end of that function. You can do this even if there is another copy of the customer file already open. Or even 5 copies open. Everything is so much easier.

Better still is to define a subclass of TDatabase for every DBF.

Code: Select all

Class TCustomers from TDatabase
   Method New()
Endclass

Method New(,"Customers") Class TCustomers
   ::use()
Return Self

Now you can simply open a customer database like this?

oCustomers:= TCustomers():New()

And even open another copy in the same function.

oCustomers2:= TCustomers():New()

Now you don't have to ever deal with aliases.

You should define a class for each database.

So many options with objects, and the code is much simpler.

James

James Bott wrote:You can open multiple copies of the same database...

   
if Empty( ::nArea ) // 2017-09-04: Prevent re-opening same dbf in multiple workareas

      if Empty( ::cAlias )
         ::cAlias := ::NewAlias()
      endif
 

Yup. If any of it failed to be opened there's no point proceeding because all of them are required, at least that's what I think.

I also would like to use net_use() to open dbfs in network environment as it'll attempt to open a dbf for a few second before giving up and display error message.

Does that mean a dbf can be opened only once?

#include "fivewin.ch"

Function Main()

   Local oCustomers,oCustomers2
   
   oCustomers:= TCustomers():new()
   
   oCustomers2:= TCustomers():new()
   
   msgInfo(oCustomers:Company,"oCustomers:Company")
   msgInfo(oCustomers:nArea,"oCustomers:nArea")
   
   msgInfo(oCustomers2:Company,"oCustomers2:Company")
   msgInfo(oCustomers2:nArea,"oCustomers2:nArea")

Return nil

Class TCustomers from TDatabase
   Method New()
Endclass

Method New(lShared) Class TCustomers
    default lShared:=.T.
    ::super():New(,"customers",,lShared)
    ::use()
Return self
 

hua wrote:Solved by subclassing TDataBase

Code: Select all

class TDataX from TDataBase
  data cFile
  method new()
endclass
method new() class TDataX
  ::super:new()
  ::cAlias := alias()
  ::nArea  := select()
return self
 

oDbf := TDatabase():New( cAlias )  // or :New( nSelect )
 

hua wrote:1. This is my existing code to use dbfs as database objects with unique aliases.

Code: Select all

method activate(cAccnFrom, cAccnTo, dFrom, dCOD, oDbCgl, lPrintable) class XBrwGL
  local oldarea := select(), dTo, cStr, a_
  local oDlg, oBrw, oFntTitl, oMFont1, oImg, bInit, oSay, oBtnCgl, nWidth, lTaxCodeAlreadyOpened, cTAccn
  local aDbfs := {                   ;
                   {"oDbHgl", "hgl", "hgl2"}, ;
                   {"oDbSaleman" , "saleman" , "saleman1"}, ;
                   {"oDbJnlhis"  , "jnlhis", "jnlhis2"}  ;
                 }

  cursorWait()
  if !OpenODbfs(aDbfs,,self)
     select (oldarea)
     return nil
  endif
//------------------------------------------------------------------------------------
function OpenODbfs(a_, lExcl, o)
  /* open dbf with unique alias
     a_ must be in the format { {<oDb name>, <dbf name>, <ntx1>, <ntx2>,..., <ntxn>} }
  */

  local lRet := .t., i, nlen := len(a_), j
  local aOpened := {}, oldarea := select()

  default lExcl := .f.


  for i := 1 to nLen
      if net_use(a_[i,2], lExcl,, cGetNewAlias( 'TDF' ))
         aadd(aOpened, select())
         if len(a_[i]) > 2
            for j := 3 to len(a_[i])
                ordListAdd(a_[i,j])
            next
            set order to 1
         endif
         o:&(a_[i,1]) := TDataBase():new()
         o:&(a_[i,1]):cFile := a_[i,2]
         o:&(a_[i,1]):setBuffer(.f.)
      else
         lRet := .f.
         exit
      endif
  next
  // fail? then close those opened so far
  if !lRet
     aeval(aOpened, {|x| (x)->(dbCloseArea())})
  endif
  select (oldarea)
return lRet
 

2. The first error I got when trying to upgrade this to Harbour+FWH19.03 is direct assignment to :cFile is no longer allowed. So I tweaked

o:&(a_[i,1]) := TDataBase():new()
o:&(a_[i,1]):cFile := a_[i,2]

to

o:&(a_[i,1]) := TDataBase():new(,a_[i,2])

3. Then I get other RTE errors. After debugging, I determined it's because :cAlias is empty. So I tweaked the code further to

Code: Select all

  for i := 1 to nLen
      cAlias := cGetNewAlias( 'TDF' )
      if net_use(a_[i,2], lExcl,, cAlias)
         ...
         o:&(a_[i,1]) := TDataBase():new(cAlias, a_[i,2])
         ...
      endif
  next
 

4. At this point RTE still occur. Now it's because :nArea is 0.
How can I set :nArea without using :SetArea()? I do not wish to use :SetArea() because it assigns :cAlias and :cFile with the same value when in my case it's not.
:cAlias is some randomly generated unique alias name while :cFile is the name of the physical dbf.

TIA

function OpenDbfs( aDbfs, lExcl, o )

   local i, j, oDbf, cErr
   local aOpened  := {}
   local lRet     := .t.

   DEFAULT lExcl := .f.

   for i := 1 to Len( aDbfs )
      oDbf  := TDatabase():Open( nil, aDbfs[ i, 2 ], "DBFNTX", !lExcl )
      AAdd( aOpened, oDbf )
      if oDbf:Used()
         for j := 3 to Len( aDbfs[ i ] )
            TRY
               oDbf:OrdListAdd( aDbfs[ i, j ] )
            CATCH
               lRet  := .f.
               cErr  := "Can not open " + aDbfs[ i, j ] + ".ntx"
               EXIT
            END
         next
      else
         lRet  := .f.
         cErr  := "Can not open " + aDbfs[ i, 2 ] + ".dbf"
      endif
      if lRet == .f.
         EXIT
      endif
   next

   if lRet
      AEval( aDbfs, { |a,i| OSend( o, "_" + a[ 1 ], aOpened[ i ] ) } )
   else
      AEval( aOpened, { |oDbf| oDbf:End() } )
      ? cErr
   endif

return lRet
 

We can understand from his code that he is using DBFNTX.

nageswaragunupudi wrote: As always, we keep advising to open the dbfs by using methods of TDatabase only.

We advise the revise the function OpenDbfs() on these lines:

Code: Select all

function OpenDbfs( aDbfs, lExcl, o )
    .
    .
    .