References and Nested Data

Array of Hashes

An array reference can hold hash references for small table-like data.

row lookup A row lookup walks entries until it finds the row with the needed value.

Array of Hashes

target
array_of_hashes.pl
Replay: real traced execution (multi-file project)
use strict;
use warnings;

my $target = "beta";
my $rows_ref = [
    { name => "alpha", score => 3 },
    { name => "beta", score => 5 },
];
my $found = "no";
my $score = 0;

foreach my $row_ref (@{$rows_ref}) {
    if ($row_ref->{name} eq $target) {
        $found = "yes";
        $score = $row_ref->{score};
    }
}

print "target=$target\n";
print "found=$found\n";
print "score=$score\n";

use strict;
use warnings;

my $target = "alpha";
my $rows_ref = [
    { name => "alpha", score => 3 },
    { name => "beta", score => 5 },
];
my $found = "no";
my $score = 0;

foreach my $row_ref (@{$rows_ref}) {
    if ($row_ref->{name} eq $target) {
        $found = "yes";
        $score = $row_ref->{score};
    }
}

print "target=$target\n";
print "found=$found\n";
print "score=$score\n";

use strict;
use warnings;

my $target = "gamma";
my $rows_ref = [
    { name => "alpha", score => 3 },
    { name => "beta", score => 5 },
];
my $found = "no";
my $score = 0;

foreach my $row_ref (@{$rows_ref}) {
    if ($row_ref->{name} eq $target) {
        $found = "yes";
        $score = $row_ref->{score};
    }
}

print "target=$target\n";
print "found=$found\n";
print "score=$score\n";

  1. $target ← beta, $found ← no, $score ← 0

    4my $target→ beta = "beta"; #@target="alpha", "gamma"5my $rows_ref = [6    { name => "alpha", score => 3 },7    { name => "beta", score => 5 },8];9my $found→ no = "no";10my $score→ 0 = 0;

  2. foreach my $row_ref (@{$rows_ref})

    pass 1 of 2
    12foreach my $row_ref (@{$rows_ref}) {13    if ($row_ref->{name} eq $target) {

  3. foreach my $row_ref (@{$rows_ref})

    pass 2 of 2
    12foreach my $row_ref (@{$rows_ref}) {13    if ($row_ref->{name} eq $target) {

  4. $found ← yes, $score ← 5

    12foreach my $row_ref (@{$rows_ref}) {13    if ($row_ref->{name} eq $targetbeta) {14        $found→ yes = "yes";15        $score→ 5 = $row_ref->{score};16    }

  5. print "target=$target ";

    19print "target=$targetbeta\n";20print "found=$foundyes\n";21print "score=$score5\n";
    outputtarget=beta
found=yes
score=5

  1. $target ← alpha, $found ← no, $score ← 0

    4my $target→ alpha = "alpha";5my $rows_ref = [6    { name => "alpha", score => 3 },7    { name => "beta", score => 5 },8];9my $found→ no = "no";10my $score→ 0 = 0;

  2. foreach my $row_ref (@{$rows_ref})

    pass 1 of 2
    12foreach my $row_ref (@{$rows_ref}) {13    if ($row_ref->{name} eq $target) {

  3. $found ← yes, $score ← 3

    12foreach my $row_ref (@{$rows_ref}) {13    if ($row_ref->{name} eq $targetalpha) {14        $found→ yes = "yes";15        $score→ 3 = $row_ref->{score};16    }

  4. foreach my $row_ref (@{$rows_ref})

    pass 2 of 2
    12foreach my $row_ref (@{$rows_ref}) {13    if ($row_ref->{name} eq $target) {

  5. print "target=$target ";

    19print "target=$targetalpha\n";20print "found=$foundyes\n";21print "score=$score3\n";
    outputtarget=alpha
found=yes
score=3

  1. $target ← gamma, $found ← no, $score ← 0

    4my $target→ gamma = "gamma";5my $rows_ref = [6    { name => "alpha", score => 3 },7    { name => "beta", score => 5 },8];9my $found→ no = "no";10my $score→ 0 = 0;

  2. foreach my $row_ref (@{$rows_ref})

    pass 1 of 2
    12foreach my $row_ref (@{$rows_ref}) {13    if ($row_ref->{name} eq $target) {

  3. foreach my $row_ref (@{$rows_ref})

    pass 2 of 2
    12foreach my $row_ref (@{$rows_ref}) {13    if ($row_ref->{name} eq $target) {

  4. print "target=$target ";

    19print "target=$targetgamma\n";20print "found=$foundno\n";21print "score=$score0\n";
    outputtarget=gamma
found=no
score=0