Detecting EOF in Random access files on fetch

[DARKNIGHT]

hello All,

I am trying to learn how to use random access files. I think I pretty much have it down,

but the only problem is, if I select a non existent record #, I get the standard LB EOF error.

and my progam crashes.

my question is: can I use the EOF statement in Random access ?

is there another method I can use to detect EOF otherwise?

thank you in advance

here is my code:

Rem Random Access test 3
OPEN "members.dat" FOR RANDOM AS #1 LEN=76
FIELD #1,_' set up the fields for file opened as #1
30 AS Name$,_ ' 1st 30 bytes contains Name$, string
40 AS Address$,_ ' 2nd 40 bytes contains Address$, string
6 AS IDnumber ' 3rd 6 bytes contains IDnumber, numeric

'gosub [Set_Data] *** Temp JSR to setup R.A files

[Fetch_Record]
locate 5,4:input"Enter Record # to search:";a
if a=0 then [Fetch_Record]
'
locate 5,7:print"======================================================================="
locate 5,8:print"| ID #: | NAME: | ADDRESS: |"
locate 5,9:print"======================================================================="

if eof(#1)<1 then [Err]
GET #1,a

'* Fill Form
locate 7,10:print IDnumber
locate 15,10:print Name$'
locate 38,10:print Address$
locate 10,20:input"Press 'Enter' to search again: -> ";r$
cls
gosub [Fetch_Record]

[Err]' NOTE: Have not found a good way to detect EOF state in RA
locate 5,6:print"<<< Record Not Found >>>"
for x=1 to 300000:next x
cls
gosub [Fetch_Record]



[Set_Data]' *** CREATES RECORDS- on first time use ***
for a=1 to 2
if a=1 then let Name$ = "John Q. Public": Address$ = "456 Maple Street, Anytown, USA":IDnumber = 9274
if a=2 then let Name$ = "Alfred R Jones":Address$ = "227 15th Av, New York New York, USA":IDnumber = 4365
PUT #1,a
next a
print"Records Written"
end

[tsh73]

Hello Jim
I think it should work like this

OPEN "members.dat" FOR RANDOM AS #1 LEN=76
'...
numRecords = lof(#1)/76   'number of records for now

for record=1 to numRecords 'so never out of that record number
'   ...
next


[DARKNIGHT]

thanks,
this logically looked like it would work, but I still get the LB EOF error if I select a non existent record #.
I never thought of using the LOF statement. you have given a new possible solution. I'll play a bit with LOF

and see if I can get this ironed out.

[Update]  I tried ' if a>lof(#1) then [Err]' before the GET statement, but that didn't work either. I'll keep

plugging along, and if I get it to work, I'll post it to the forum for others who might be getting the same EOF Error

in RAF.

[Chris Iverson]

In your code in your update, you forgot to multiply "a" by the record length when comparing for the error.

"a" is the record number, but lof() measures the length of the file in bytes.

If you want to find out if record "a" is past the length of the file, you need to compare bytes to bytes by multiplying "a" by the record length.

In your earlier example, you have a record length of 76, so try "if (a * 76) > lof(#1) then [Err]".

[DARKNIGHT]

Hey Chris,

that worked! THANKS Man!

you Rock Bro! 

I copied and pasted that formula to put in my reference folder,

for coding in LB