使用存储在数组中的比较运算符

Question

I have the following example array:

$comparisons = array(
    0 => array(
        'method'    => 'productTotalQuantity',
        'operator'  => '>=',
        'value'     => '2'
    ),
    1 => array(
        'method'    => 'productTotalWeight',
        'operator'  => '<=',
        'value'     => '10'
    )
);

I have invented this array structure, so it can be altered if required. I am trying to somehow evaluate the operator key, so that I can achieve something along the lines of:

foreach ($comparisons as $comparison) {
    $value = $this->$comparison['method']($product);
    // E.g. $value = $this->productTotalQuantity($product)
    // $value could = 4

    if ($value $comparison['operator'] $comparison['value']) {
        // Comparison successful
        $matches[] = TRUE;
    }
}

if (count($matches) == count($comparisons)) {
    // All comparisons were successful. Apply the discount.
}

If you have time, a full code example of how to parse this array would be extremely helpful. I've been working on it for about 20 hours straight and think I'm about to literally bash my head against a brick wall. If you are familiar with Magento, I am trying to somewhat mimic the functionality of the "Shopping Cart Price Rule" Conditions in Promotions.

Answer 1

"translating" operations from strings to real operations is mostly dirty and or evil :-) you need a lot of conditional code (if-else) or eval (but everybody knows: eval is evil ^^)

I would use an object-oriented approach, since PHP does support object orientation (I don't know the exact php syntax, it has been a while ;-)) and I give you pseudo code to enforce the ideas:

class AbstractComparator {
   boolean static compare($operand1, $operand2);   
}

class EqualsComparator extends AbstractComparator {
   @Override
   boolean static compare($operand1, $operand2) {
      return ($operand1 == $operand2);
   }
}

// Now use one of the subclasses in your datastructure
$comparisons = array(
0 => array(
    'method'    => 'productTotalQuantity',
    'operator'  => EqualsComparator,
    'value'     => '2'
),
1 => array(
    'method'    => 'productTotalWeight',
    'operator'  => SmallerThanComparator,
    'value'     => '10'
)
);

$allComparisonsSuccessful = true;
foreach ($comparisons as $comparison) {
   $value = $comparison['operator'].equals($product);
    // Use the AND operator... full predicate is only true if all elements are true
   $allComparisonsSuccessful = $allComparisonsSuccessful && $value;
}