在 Perl 中使用 foreach 代替 map 和 grep

Question

I am trying to convert the map and grep code totally to foreach loop, but I am facing trouble when I do it.

Here is the array code to get the events

my @events = [
  {
    Sponsor => ’Saash’,
    Time => ’05:00’,
    Date => ’01-03-2021’,
  },
  {
    Sponsor => ’Saash Tech’,
    Time => ’03:00’,
    Date => ’01-03-2021’,
  },
  {
    Sponsor => ’Saash Technology’,
    Time => ’04:00’,
    Date => ’01-03-2021’,
  },
  {
    Sponsor => ’Saash Techs’,
    Time => ’05:00’,
    Date => ’01-03-2021’,
  },
];

my $time = ’05:00’;

Here is the code used in grep and map:

my $data = [
    map
    {
        my $hide;
        if ($_->{'sponsor'}) {
            $_->{'sponsor'} =~ ‘SaAsh’;
            $_->{‘sponsor'} = ‘Saash’ if $_->{’sponsor’} eq 'Saash Techs';
            if ($_->{‘time'} eq ’04:00’ && $_->{‘sponsor'} eq ‘SaAsh’) ) {
                $hide = 1;
            }
        }
        $hide ? () : ( $_ );
    }
    grep { $_->{‘time} =~ $time } @{events}
];

Below is the code where I have converted from grep map to foreach

my $data;
foreach my $event (@events) {
    if ($event->{‘time’} =~ ’07:00’) {
        my $hide;
        if ($event->{‘sponsor’}) {
            $event->{‘sponsor'} =~ ‘SaAsh’;
            $event->{'sponsor'} = ‘Saash’ if $event->{’sponsor’} eq ‘Saash Techs';
            if ($event->{'time'} eq '04:00' && $event->{'sponsor'} eq ‘SaAsh’) ) {
                $hide = 1;
            }
        }
        $hide ? () : ( $event );
    }
}
$data = [$event];

I am not getting the same output in foreach code when compared to the code of grep and map.

Can someone help where am I going wrong?

Answer 1

foreach my $event (@events) {
   ...
   $hide ? () : ( $event )
}

$data = [$event];

should be

foreach my $event (@events) {
   ...
   push @$data, $hide ? () : ( $event )
}

---

my @a = map BLOCK LIST; can be written as

my @a;
for (LIST) {
   push @a, do BLOCK;
}

my @a = grep BLOCK LIST; can be written as

my @a;
for (LIST) {
   push @a, $_ if do BLOCK;
}

Of course, the do can be removed through simplification and refactoring, and the two loops can be combined in your case. After performing the above transformations and some cleanup, we get the following:

for my $event (@events) {
   $event->{sponsor} = 'Saash'
      if $event->{sponsor}
      && $event->{sponsor} eq 'Saash Techs';
}

my $data = [];
for my $event (@events) {
   next if $event->{time} ne $time;
   next
      if ($event->{sponsor}
      && $event->{sponsor} eq 'SaAsh'
      && $event->{time} eq '04:00';

   push @$data, $event;
}

You were only changing some of the Saash Techs sponsors to Saash in @events , which is why I do the fixes first. It was a bad practice to change @events surreptitiously like you were doing anyway.

Answer 2

Is this the answer code?

foreach my $event (@events) {
   next if $_->{time} !~ /$time/;

   if ($event->{'sponsor'}) {
      $event->{'sponsor'} =~ ‘SaAsh’;
      $event->{'sponsor'} = 'Saash' if $event->{'sponsor'} eq 'Saash Techs';
      if ($event->{'time'} eq '04:00' && $event->{'sponsor'} eq ‘SaAsh’) ) {
          $hide = 1;
      }
   }

   push @$data, $hide ? () : ( $event );

}