Welcome to the Factory!
The Factory mixin provides a robust Factory implementation. Overrides are automatically registered upon sub-classing. Manual override and disables are available if auto-registration does not result in the desired factory overrides. Manual overrides are available at the class and global granularities. Method arguments can be passed in as strings or symbols so that overrides can be set even before classes have been defined.
Using the Factory
The Factory module should be included in the classes which you want to provide factory overrides.
class ParentClass include Factory def initialize arg=nil @arg = arg end end
Inheriting from this class will automatically register the sub-class as the override of the parent class.
class Child1 < ParentClass end
Sub-classes need not include Factory though doing so should not hurt anything. The create class method is implemeted by the mixin for the parent class and all sub-classes. Constructor arguments can be passed similarly through create.
ParentClass.create('hello') # Returns an object of type Child1
Subsequent sub-classing updates the factory overrides.
class Child2 < Child1 end ParentClass.create # Returns an object of type Child2 Child1.create # Returns an object of type Child2 ParentClass.new # Works normally. Returns an object of type ParentClass. class Child3 < ParentClass end ParentClass.create # Returns an object of type Child3 Child1.create # Returns an object of type Child2 since Child3 is not a decendent.
Manual Factory Overrides
If the resulting factory overrides are not what is desired, they can be manually overriden. The methods that are discussed in the section takes arguments which are the class constants
or as a symbol (strings are also accepted).
This allows overrides to be used even before a class is defined.
Factory Override Disable
Continuing from the above example ParentClass has a factory override of Child3 since it was the last sub-class to inherit from it. If the intention is to have Child2 be the factory override there are several ways this can be accomplished. To disable a class from overriding a particular class either of the following can be used.
Factory.disable_override ParentClass, Child3 ParentClass.create # Returns an object of type Child2
ParentClass.disable_factory_override Child3 ParentClass.create # Returns an object of type Child2
Since the disable is with respect to a specific ancestor, other ancestors are uneffected.
Factory Override Enable
Another way of manually configuring overrides is through enabling an override. This can also be used to cancel an existing class specific factory disable override.
Factory.enable_override ParentClass, Child3 ParentClass.create # Returns an object of type Child3
The last override enable takes presedence.
Factory.enable_override ParentClass, Child2 ParentClass.create # Returns an object of type Child2
ParentClass.enable_override Child2 ParentClass.create # Returns an object of type Child2
Subsequent calls of the disable override methods will cancel the previous enable overrides on the same types.
Global Factory Override Methods
To disable a class from overriding any classes use the following,
To cancel the disable override,