how do I develop a multithreading application within PowerBuilder classic?

[Former Member]

hi guys

there was a legacy program need to maintain,then I tried to check a batch number of product that if supplies was less than all sells,I believe it's a good experience for

colleagues that after scaned the barcode of that batch number application then checked the supplies and sells aysnchrously.althought I have searched Google,however Powerbuilder is less infomation I could found about multithreading,it's not a clear instrution in Powerbuilder help as well.

I'm not sure two questions about multithreading within powerbuilder

#1 if the exception is going to occur when SharedObjectRegister the same name when open two windows like following?

code:

window w_1
opensheet(w_1,"w_inv",w_main,0,Original! )

// then in two same w_inv windows exectue SharedObjectRegister with same name in a //same time,is it going to ocurr the exception?

SharedObjectRegister ('nov_checkvalidobject', ls_var)

#2 some pages said that main thread and sub thread are independent,does it mean that if need to execute SQL select syntax,I can't use sqlca transaction which has connected to a database in main thread?

please take a look at my code,please give me suggestion that I have done wrong or should be aware.thanks in advance

//w_inv instance variable:

//long ll_multithreadcount
//string is_sbmodel
//nov_checkvalidobject tarea_No[ ]

//this is wf_multithread_cal

//long as_row

string ls_var
ErrorReturn ler_error
long ll_threadcurrent



ll_threadcurrent=ll_multithreadcount
ls_var = 'objeto_' +string(ll_threadcurrent)


if is_new='0' then
cb_add_main.enabled=false

elseif is_new='1' then
cb_delete_main.enabled=false
cb_delete_sub.enabled=false
end if

ler_error = SharedObjectRegister ('nov_checkvalidobject', ls_var)

choose case ler_error
case SharedObjectExistsError!

messagebox("Error","The instance name is already used",stopsign!)

if is_new='0' then
cb_add_main.enabled=true

elseif is_new='1' then
cb_delete_main.enabled=true
cb_delete_sub.enabled=true
end if

return -1
case SharedObjectCreateInstanceError!

messagebox("Error","The object could not be created",stopsign!)

if is_new='0' then
cb_add_main.enabled=true

elseif is_new='1' then
cb_delete_main.enabled=true
cb_delete_sub.enabled=true
end if

return -1

case SharedObjectCreatePBSessionError!

messagebox("Error","The object in the session could not be created",stopsign!)

if is_new='0' then
cb_add_main.enabled=true

elseif is_new='1' then
cb_delete_main.enabled=true
cb_delete_sub.enabled=true
end if

return -1
end choose


ler_error = SharedObjectGet (ls_var, tarea_No[ll_threadcurrent])
choose case ler_error
case SharedObjectCreateInstanceError!

messagebox("Error","The local reference to the shared object could not be created",stopsign!)

if is_new='0' then
cb_add_main.enabled=true

elseif is_new='1' then
cb_delete_main.enabled=true
cb_delete_sub.enabled=true
end if

return -1
case SharedObjectNotExistsError!

messagebox("Error","The instance name is not registered ",stopsign!)

if is_new='0' then
cb_add_main.enabled=true

elseif is_new='1' then
cb_delete_main.enabled=true
cb_delete_sub.enabled=true
end if

return -1
end choose

tarea_No[ll_threadcurrent].POST of_checkvalid(dw_2,as_row)

SharedobjectUnregister(ls_var)

ll_multithreadcount++

if is_new='0' then
cb_add_main.enabled=true

elseif is_new='1' then
cb_delete_main.enabled=true
cb_delete_sub.enabled=true
end if

return 0

//nov_checkvalidobject: there is a function in nov_checkvalidobjec which is of_checkvalid

// there is 2 parameters in it

//paramter #1 datawindow as_dw

//paramter #2 long as_therow

//of_checkvalid function code:

decimal ld_invnum,ld_depnum
string ls_prodno,ls_batchno,ls_prodadd

if as_therow<0 or as_therow>as_dw.rowcount() then return -1

ls_prodno=as_dw.getitemstring(as_therow,"prod_no")
ls_batchno=as_dw.getitemstring(as_therow,"batch_no")
ls_prodadd=as_dw.getitemstring(as_therow,"prod_add")

if isnull(ls_prodno) or trim(ls_prodno)="" or isnull(ls_batchno) or trim(ls_batchno)="" or isnull(ls_prodadd) or trim(ls_prodadd)="" then return -2
//check the number of all sells
select isnull(sum(inv_num),0) into :ld_invnum from inv_sub where prod_no=:ls_prodno and batch_no=:ls_batchno and prod_add=:ls_prodadd;

//check the number of all suppliers

select isnull(sum(dep_num),0) into :ld_depnum from dep_sub where prod_no=:ls_prodno and batch_no=:ls_batchno and prod_add=:ls_prodadd;

if ld_invnum>ld_depnum then
as_dw.setitem(as_therow,"if_is_valid","failed")
return -3
end if


as_dw.setitem(as_therow,"if_is_valid","pass")
return 0

[Former Member · Accepted solution]

Hi,

#1: The name must be unique for registered objects in the application. If you try to register a second object with the same name the function SharedObjectRegister should return SharedObjectExistsError!

You may use a shared or global variable instead of instance variable as thread counter.

#2: You can't use the transaction object from main thread (SQLCA) in a shared object. You need a separate database connection for each shared object if you want to access the database.

One parameter of function of_checkvalid of your shared object is a datawindow control. I think the shared object cannot access this object from main thread. You may pass only nonvisualobjects. If you want to check data from a datawindow you may pass it as blob (see function GetFullState / SetFullState).

To return a result from shared object to main thread you need a (nonvisual) callback object with a function you can call from the shared object.

HTH