topic Re: How to limit length of variable? in QlikView

How to limit length of variable?

Thu, 26 Jan 2017 10:52:39 GMT

Hi everyone!

I'm developing an analysis tool for one of our customers in QV.. one feature of this app is the possibility to log the selections made by the user. This is realized through a variable which is refreshed with every action: its content gets thereby expanded with a timestamp (now()) and the current selection status (GetCurrentSelections()) in a new row (chr(13)). The content of the variable is displayed in a text box on a separate sheet. Thus, the user can explore the data and afterwards reproduce its actions through the log. Although this is already working very well, I would like to limit the variable to something like 300 rows (=300 last actions) because of performance aspects. I already added the possibility to clear the log-variable through a button manually. However, since the user might forget to push this button every now and then, an automatic solution seems reasonable..

I'm wondering if there is a possibility to limit the length of a variable row-wise? Only hint I found so far was using "autocommenting expression" but neither I wasn't sure if this really addresses my issue nor wasn't I able to implement it. Do you have any ideas how to solve this task?

Thank you!

Re: How to limit length of variable?

MarcoWedel — Sat, 28 Jan 2017 23:36:40 GMT

Hi,

maybe one solution might be:

=Now()&': '&GetCurrentSelections(' // ')&Chr(13)&Left(vSelHist&Repeat(Chr(13),9),Index(vSelHist&Repeat(Chr(13),9),Chr(13),9))

(replace 9 with max rows-1)

hope this helps

regards

Marco

Re: How to limit length of variable?

vinieme12 — Mon, 30 Jan 2017 08:07:34 GMT

create a counter variable to increment on every selection

and add condition to add to selection list only if counter variable value <300

Re: How to limit length of variable?

jonathandienst — Mon, 30 Jan 2017 08:43:41 GMT

I think you can simplify this to a set variable action with expression

=Now() & ': ' & GetCurrentSelections() & Chr(10) & Left(vSelHist, Index(vSelHist, Chr(10), -1))

Will always drop off the last row, so this assumes that log file is already has the correct number of lines. You could create a 200 blank line starting value in a text editor, and paste that into the variable overview or use Repeat(chr(10), 200) in a set in the load script.

Re: How to limit length of variable?

Tue, 31 Jan 2017 10:32:43 GMT

Thanks for this great solution! Only disadvantage in my case is that the excel-export of the log now always is 300 lines long with a lot of line breaks..but I guess I can live with that.

Re: How to limit length of variable?

Tue, 31 Jan 2017 10:46:54 GMT

Thanks for your help! I have no idea why, but for some reason it didn't work in my application.. The initial pasted amount of line breaks is kept under the actual log history and therefore the variable isn't limited. However, I solved it with Marco's approach-

Re: How to limit length of variable?

MarcoWedel — Tue, 31 Jan 2017 22:17:03 GMT

Hi,

I'm glad it worked.

Regarding the line breaks, maybe you could use this expression instead:

=Now()&': '&GetCurrentSelections(' // ')&Chr(13)&Chr(10)&If(SubStringCount(vSelHist,Chr(13)&Chr(10))<=9,vSelHist,Left(vSelHist,Index(vSelHist,Chr(13)&Chr(10),9)+1))

hope this helps

regards

Marco