Consider a chemical mixture with a bunch of ingredients. Both mixture
and ingredients are instances of the same class so they have the same
fields. They also have many related models, including 1:1, 1:n and n:m.
Each related model will have none or many TextField's.
The objective is to programmatically fill empty mixture text fields with
concatenated content from the ingredients. The concatenated content
would be separated by ingredient name titles for the user to deal with
the content more easily.
I don't necessarily need all mixture text fields filled this way but it
certainly makes sense for some. With a couple of related models I'd
concatenate all text fields, with most though I'd like to pick and
choose by field name and I'd ignore some models completely.
The following model method is working properly as described but it is
mostly boiler-plate. It also only covers the first few of a large number
of related models with text fields. If I keep using this technique it
will add hundreds of LOC. Yuk.
The question is how can I refactor this and make it generic? Perhaps
using the _meta API?
Any guidance appreciated
(In the abstract ancestor class of the Solid, Liquid and Gas classes)
def concat_fields(self, ingredients): """ ingredients is a queryset of
substance-to-substance m2m records. A substance has one physical state
object being gas, liquid or solid each of which inherits from
core_fields and the fields *here* we wish to concatenate text from (at
the moment) all come from core_fields. """ assert ingredients # populate
the list of ingredient physical state objects state_objs = list() for
m2m in ingredients: # substance has physical state so it knows which
model to return
state_objs.append(m2m.ingredient.get_physical_state_object()) # get the
text concatenated if not self.stability_comment: comment = "" for obj in
state_objs: if obj.stability_comment: name = obj.substance.name text =
obj.stability_comment comment = "{0}\n{1}: {2}".format(comment, name,
text) comment = comment.strip() if comment: self.stability_comment =
comment # and repeat if not self.reactivity: comment = "" for obj in
state_objs: if obj.reactivity: name = obj.substance.name text =
obj.reactivity comment = "{0}\n{1}: {2}".format(comment, name, text)
comment = comment.strip() if comment: self.reactivity = comment # ad
nauseam if not self.reaction_hazards: comment = "" for obj in
state_objs: if obj.reaction_hazards: name = obj.substance.name text =
obj.reaction_hazards comment = "{0}\n{1}: {2}".format(comment, name,
text) comment = comment.strip() if comment: self.reaction_hazards =
comment if not self.avoid: comment = "" for obj in state_objs: if
obj.avoid: name = obj.substance.name text = obj.avoid comment =
"{0}\n{1}: {2}".format(comment, name, text) comment = comment.strip() if
comment: self.avoid = comment if not self.incompatibilities: comment =
"" for obj in state_objs: if obj.incompatibilities: name =
obj.substance.name text = obj.incompatibilities comment = "{0}\n{1}:
{2}".format(comment, name, text) comment = comment.strip() if comment:
self.incompatibilities = comment
Thanks
Mike
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