Data Mapper Pattern: Complexe query from Service Layer

Question

I\'m sing the Data Mapper Pattern in Zend Framework. This works well so far, but now I got to a point where I need your help/opinion. So let\'s start with the Code:

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Answer 1

Indeed, for two conditions, it inadvisable to query on one condition and then filter on your other while you iterate. It leaves you no clear approach for more than two conditions. And implementing pagination adapters becomes pretty messy.

Seems to me that the issue is that your mapper fetch() method supports permits only a single condition. So:

1. Modify the signature to support an array of conditions.

2. Alternatively, you could create a separate mapper method for each enhanced fetch method, ex: fetchByHairAndAge($hair, $age), etc.

Answer 2

In my limited experience with data mappers I have found the following approach to work quite well for the scenarios I have encountered so far:

public function getPeopleByHaircolorAndAge($haircolor, $age, $limit=null, $offset=null)
{
    $people = new PersonCollection;
    $people->filterByHaircolor($haircolor);
    $people->filterByAge($age);
    $people->setLimit($limit);
    $people->setOffset($offset);

    $personCollectionMapper = new PersonCollectionMapper;
    $personCollectionMapper->fetch($people);

    return $people;
}

By instantiating the domain object first I have the option to set filters and other variables that the data mapper can read from the object when it is injected into the mapper.

To me this has been the superior approach so far compared to having multiple mapper methods that returns a domain object.