(extract intro!) see
Table of Contents
Consistency¶
An ERP5 can manage so many objects that we probably want to check how strong
they are. Many objects have many relations with others objects, and it's possible
that one of them could be broken for any reason (for example the object pointed
was deleted). An object could have some mandatory data, but for some reasons,
we can't put them when this object is created, so we have to check at some
moment whenever or not those mandatory data are present or not.
Definition of the consistency¶
The definition of the consistency will be defined inside the PropertySheet of
our object. This is an example :
_constraints = (
{ 'id' : 'forme',
'description' : 'There must be one and one only Forme',
'type' : 'CategoryExistence',
'portal_type' : ('Forme',),
'base_category' : ('specialise',),
'message_category_not_set': 'Forme must be defined',
},
{ 'id' : 'gamme',
'description' : 'There must be one or two Gamme',
'type' : 'CategoryMembershipArity',
'min_arity' : '1',
'max_arity' : '2',
'portal_type' : ('Gamme',),
'base_category' : ('specialise'),
'message_arity_not_in_range': 'One or Two Gamme must be defined',
},
)
As you can see, we needs to set properly the constraint. In this example we
want to check category membership of two components of an object. So we should
create two constraints inside the
PropertySheet, one for each component from which we want to check the arity.
So for each constraint we first give an id and a description.
The type corresponds to the name of the class inside the ERP5/Constraint folder.
Here this we use CategoryExistence and CategoryMembershipArity. You can have a
look at this class in svn
from Constraint import Constraint
class CategoryMembershipArity(Constraint):
"""...
"""
"""
Every specific Constraint class have to be a subclass of Constraint
and should have at least one method : checkConsistency. This is what we can see
in CategoryMembershipArity:
def checkConsistency(self, obj, fixit=0):
"""...
"""
The fixit parameter of checkConsistency can be used in order to fix problems.
Indeed, most of the time, it's almost the same code if we want to find
inconsistencies or if we want to fix them. So instead to create a fixConsistency
with a code very similar to checkConsistency, by subclassing the Constraint
class, we already have a fixConstency method defined like this :
def fixConsistency(self, obj):
"""
Default method is to call checkConsistency with
fixit set to 1
"""
return self.checkConsistency(obj, fixit=1)
Like this, inside your checkConsistency method, when you found an error, you can
simply add :
if fixit==1:
do_whatever_to_fix
Conditional constraints¶
It is possible to check conditions for constraints. For example, it might be
needed to check for given constraint, only if object is related to specific
object or have specific state.
Condition is defined in PropertySheet constraint definition:
_constraints = (
{ 'id' : 'conditional_forme',
'description' : 'There must be one and one only Forme',
'type' : 'CategoryExistence',
'portal_type' : ('Forme',),
'base_category' : ('specialise',),
'message_category_not_set': 'Forme must be defined',
'condition' : 'python: object.getSimulationState() not in ["draft","invalidated"]',
},
)
In above example, constraint will be only checked if object is not in draft or
invalidated states.
Creating conditional constraints¶
Note: I thought it will work without below, but it is not. Am I wrong? (ŁukaszNowak)
In top of checkConsistency method of your Constraint class there is need to
check for constraint condition:
def checkConsistency(self, obj, fixit=0):
"""...
"""
if not self._checkConstraintCondition(obj):
return []
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