However, the Footballer class can delegate these columns to the Player class. The footballer table doesn't own the identity columns, which are in the player table. Use inherited objects just like you use regular Propel model objects: If you define an tag with no extends attribute, as in the example above, it must use the table phpName as its class attribute. That mean that you can add a Manga kind of book that extends Comic instead of Book. The Essay and Comic classes extend the Book class, the EssayQuery and ComicQuery classes extend BookQuery.Īn inherited class can extend another inherited class. Once you rebuild your model, Propel generated all three model classes ( Book, Essay, and Comic) and three query classes ( BookQuery, EssayQuery, and ComicQuery). Note that this 'key' column must be a real column in the table. The column needs the inheritance="single" attribute to make Propel understand that it's the class key column. Classically, this column is named class_key - but you can choose whatever name fits your taste. Schema DefinitionĪ table using Single Table Inheritance requires a column to identify which class should be used to represent the table row.
With single table inheritance, the data of all three classes is stored in one table, named book. Consider an object model with three classes, Book, Essay, and Comic - the first class being parent of the other two. Let's illustrate this idea with an example. This has the implication that your table must have all columns needed by the main class and subclasses. In this implementation, one table is used for all subclasses. Propel offers three types of table inheritance: Single Table Inheritance, which is the most efficient implementations from a SQL and query performance perspective, but is limited to a small number of inherited fields Class Table Inheritance, which separates data into several tables and uses joins to fetch complete children entities, and Concrete Table Inheritance, which provides the most features but adds a small overhead on write queries. Inheritance being an object-oriented notion, it doesn't have a true equivalent in the database world, so this is something an ORM must emulate. Developers often need one model table to extend another model table.
0 kommentar(er)
