Question

I created a collection by adding items to a Varien_Data_Collection collection object.

$collection = new Varien_Data_Collection();
  foreach($array_of_products as $productId){
    $collection->addItem(Mage::getModel('catalog/product')->load($productId));
}

However when this object is passed on to Magento pager block as given below, it breaks the pagination in my custom page.

$pager = $this->getLayout()->createBlock('page/html_pager', 'retailerfe.analysis.pager')
            ->setCollection($collection);

P.S I have never had problems with collections fetched from
model collections like Mage::getModel(‘module/modelname’)->getCollection(). It is just collections created by adding items to a Varien_Data_Collection Object.

Answer 1

The pager is calling setPageSize on your collection which – if you trace it – is only used by getLastPageNumber. This means the pager can show the number of pages accurately but that’s it. It is Varien_Data_Collection_Db that actually does anything with the current page number and size by rendering them as a LIMIT clause for SQL.

To create a collection that respects the page criteria you will have to create a descendant to the class. For ideas look at the source of Varien_Data_Collection_Filesystem and how it implements loadData.

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I’ve just re-read your question and realised you can do this:

$collection = Mage::getModel('catalog/product')->getCollection()
            ->addIdFilter($array_of_products);

This collection will page quite happily.