Real cases you use Factory (method) pattern and the benefits

Question

Hi folks:

Can you provide practices about leveraging Factory (method) pattern? And the benefit you got greatly.

Thanks.

Answer 1

.Net System.Data.Common.DbProviderFactory class can be used for writing a DB-independent code.

var factory = DbProviderFactories.GetFactory(/* here you put provider name, e.g. taken from config */);
using (var connection = factory.CreateConnection())
using (var command = connection.CreateCommand())
{
    connection.ConnectionString = /* some connection string, e.g. from config */;
    command.CommandText = /* some query */;
    command.ExecuteNonQuery();
}

Something like this.

Answer 2

This pattern is quite prevalent in OO frameworks. It's used because it gives the framework control over the creation of objects. You can then use it for a variety of things, caching your objects, using it to force singletons, error-checking (does the object you requested exist?), logging and pretty much anything else you want to happen when someone instantiates a class.

As a side-effect it also makes for nice code. For example in PHP instead of

$person = new Person();
$person->setName('Mike');

you can do

$person = $this->load('Person')->setName('Mike');