foreach problem

Nik has asked for the wisdom of the Perl Monks concerning the following question:

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Re: foreach problem by Abigail-II (Bishop) on May 18, 2004 at 14:33 UTC
Well, your problem seems to come from the fact that foreach file, you print 4 buttons. So you have 4 times as many buttons as you have files - no wonder you get duplicates. Do something like: `print start_from (...); print table (...); s/[\/\\](.)/$1/ for @files; while (@files >= 4) { print Tr ({...}, map {td (submit (-name => 'file', -value => $_))} + splice @files => 0, 4); } print Tr ({...}, (map {td (submit (-name => 'file', -value => $_))} @f +iles), map {td ()} 1 .. (4 - @files)) if @files` [download] Abigail	[reply] [d/l]
Re: foreach problem by sgifford (Prior) on May 18, 2004 at 14:33 UTC
The problem is that all four buttons are inside the same loop iteration, so `$_` is set to the same thing all four times you call it. What you want is something like this (untested): `my @cols = (); foreach (@files) { $_ =~ s/.[\/\\](.)/$1/; push(@cols,td(submit(-name => 'file', -value => $_)); if (@cols == 4) { print Tr({-alien => 'center'}, @cols); @cols=(); } } if (@cols) { while (@cols < 4) { push(@cols,td(' ')); } print Tr({-alien => 'center'}, @cols); }` [download] That builds up a row, and prints it when it's finished. For the last row, it creates cells with a single non-breaking space in them, which avoids formatting annoyances in some browsers.	[reply] [d/l] [select]
Re: foreach problem by punkish (Priest) on May 18, 2004 at 14:32 UTC
This is happening because the special var $_ is referring to the array element received in a particular for loop. What you really want is an array of 4-element arrays for the buttons. Then you can have a foreach inside another foreach... `foreach my $thesebuttons (@aoa) { my @b = @$thesebuttons; foreach my $thisbutton (@b) { code for printing out this button... } }` [download]	[reply] [d/l]
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Re: foreach problem by sacked (Hermit) on May 18, 2004 at 14:43 UTC
In each iteration of your `foreach` loop, `$_` is set to one value in `@files`. As your call to `Tr` is inside the `foreach` loop, `$_` has the same value in each `td`. You can use `map` to iterate over the list of files and get the results you want. Also, note the use of File::Basename::basename instead of a regular expression to remove the directory from the filenames: `use File::Basename; # ... # 4 elements at a time while( my @cols= splice @files, 0, 4 ) { print Tr( {-align=>'center'}, map { td( $_ ? submit(-name=>'file', -value=> basename($_)) : ' ' + ) } @cols[0..3] ); }` [download] Or, use the distributive properties of the HTML shortcuts provided by CGI.pm (see the pod). In this case, we are passing a reference to a list of values to `td`, rather creating a list of calls to `td`: `use File::Basename; # ... while( my @cols= splice @files, 0, 4 ) { print Tr( {-align=>'center'}, td([ map { $_ ? submit(-name=>'file', -value=> basename($_)) : ' ' } @cols[0..3] ]) ); }` [download] --sacked	[reply] [d/l] [select]
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Re: foreach problem by Roy Johnson (Monsignor) on May 18, 2004 at 18:39 UTC
You might find this easy to understand: `for(my $x=0; $x<$#files+4; $x+=4) { @four_files = @files[$x..$x+3]; print Tr( {-align=>'center'}, td( submit(-name=>'file', -value=>$f +our_files[0] )), td( submit(-name=>'file', -value=>$f +our_files[1] )), td( submit(-name=>'file', -value=>$f +our_files[2] )), td( submit(-name=>'file', -value=>$f +our_files[3] ))); }` [download] The PerlMonk `tr///` Advocate	[reply] [d/l]