Model Introspection At Runtime

In addition to the object and peer classes used to do C.R.U.D. operations, Propel generates an object mapping for your tables to allow runtime introspection.

The intospection objects are instances of the map classes. Propel maps databases, tables, columns, validators, and relations into objects that you can easily use.

Retrieving a TableMap

The starting point for runtime introspection is usually a TableMap. This objects stores every possible property of a table, as defined in the schema.xml, but accessible at runtime.

To retrieve a table map for a table, use the getTableMap() static method of the related peer class. For instance, to retrieve the table map for the book table, just call:

<?php
$bookTable = BookPeer::getTableMap();

TableMap properties

A TableMap object carries the same information as the schema. Check the following example to see how you can read the general properties of a table from its map:

<?php
echo $bookTable->getName();          // 'table'
echo $bookTable->getPhpName();       // 'Table'
echo $bookTable->getPackage();       // 'bookstore'
echo $bookTable->isUseIdGenerator(); // true

Tip
A TableMap object also references the DatabaseMap that contains it. From the database map, you can also retrieve other table maps using the table name or the table phpName:

<?php
$dbMap = $bookTable->getDatabaseMap();
$authorTable = $dbMap->getTable('author');
$authorTable = $dbMap->getTablebyPhpName('Author');

To introspect the columns of a table, use any of the getColumns(), getPrimaryKeys(), and getForeignKeys() TableMap methods. They all return an array of ColumnMap objects.

<?php
$bookColumns = $bookTable->getColumns();
foreach ($bookColumns as $column) {
  echo $column->getName();
}

Alternatively, if you know a column name, you can retrieve the corresponding ColumnMap directly using the of getColumn($name) method.

<?php
$bookTitleColumn = $bookTable->getColumn('title');

The DatabaseMap object offers a shortcut to every ColumnMap object if you know the fully qualified column name: php <?php $bookTitleColumn = $dbMap->getColumn('book.TITLE');

ColumnMaps

A ColumnMap instance offers a lot of information about a table column. Check the following examples:

<?php
$bookTitleColumn->getTableName();    // 'book'
$bookTitleColumn->getTablePhpName(); // 'Book'
$bookTitleColumn->getType();         // 'VARCHAR'
$bookTitleColumn->getSize();         // 255
$bookTitleColumn->getDefaultValue(); // null
$bookTitleColumn->isLob();           // false
$bookTitleColumn->isTemporal();      // false
$bookTitleColumn->isEpochTemporal(); // false
$bookTitleColumn->isNumeric();       // false
$bookTitleColumn->isText();          // true
$bookTitleColumn->isPrimaryKey();    // false
$bookTitleColumn->isForeignKey();    // false
$bookTitleColumn->hasValidators();   // false
$bookTitleColumn->isPrimaryString(); // true

ColumnMap objects also keep a reference to their parent TableMap object:

<?php
$bookTable = $bookTitleColumn->getTable();

Foreign key columns give access to more information, including the related table and column:

<?php
$bookPublisherIdColumn = $bookTable->getColumn('publisher_id');
echo $bookPublisherIdColumn->isForeignKey();         // true
echo $bookPublisherIdColumn->getRelatedName();       // 'publisher.ID'
echo $bookPublisherIdColumn->getRelatedTableName();  // 'publisher'
echo $bookPublisherIdColumn->getRelatedColumnName(); // 'ID'
$publisherTable = $bookPublisherIdColumn->getRelatedTable();
$publisherRelation = $bookPublisherIdColumn->getRelation();

RelationMaps

To get an insight on all the relationships of a table, including the ones relying on a foreign key located in another table, you must use the RelationMap objects related to a table.

If you know its name, you can retrieve a RelationMap object using TableMap::getRelation($relationName). Note that the relation name is the phpName of the related table, unless the foreign key defines a phpName in the schema. For instance, the name of the RelationMap object related to the book.PUBLISHER_ID column is 'Publisher'.

<?php
$publisherRelation = $bookTable->getRelation('Publisher');

alternatively, you can access a RelationMap from a foreign key column using ColumnMap::getRelation(), as follows:

<?php
$publisherRelation = $bookTable->getColumn('publisher_id')->getRelation();

Once you have a RelationMap instance, inspect its properties using any of the following methods:

<?php
echo $publisherRelation->getType();     // RelationMap::MANY_TO_ONE
echo $publisherRelation->getOnDelete(); // 'SET NULL'
$bookTable      = $publisherRelation->getLocalTable();
$publisherTable = $publisherRelation->getForeignTable();
print_r($publisherRelation->getColumnMappings());
  // array('book.PUBLISHER_ID' => 'publisher.ID')
print_r(publisherRelation->getLocalColumns());
  // array($bookPublisherIdColumn)
print_r(publisherRelation->getForeignColumns());
  // array($publisherBookIdColumn)

This also works for relationships referencing the current table:

<?php
$reviewRelation = $bookTable->getRelation('Review');
echo $reviewRelation->getType();     // RelationMap::ONE_TO_MANY
echo $reviewRelation->getOnDelete(); // 'CASCADE'
$reviewTable = $reviewRelation->getLocalTable();
$bookTable   = $reviewRelation->getForeignTable();
print_r($reviewRelation->getColumnMappings());
  // array('review.BOOK_ID' => 'book.ID')

To retrieve all the relations of a table, call TableMap::getRelations(). You can then iterate over an array of RelationMap objects.

Tip
RelationMap objects are lazy-loaded, which means that the TableMap will not instanciate any relation object until you call getRelations(). This allows the TableMap to remain lightweight for when you don't use relationship introspection.