[sqlalchemy] association_proxy as property?
Hello, To generate json from our SQLAlchemy model objects, we are using iterate_properties to determine how to dictify the object. One of our objects uses association_proxy which we would like to represent in the JSON. Unfortunately, because it is not a property, the dictification misses this property. I feel like I am missing something simple here. How can I make an association_proxy appear to be a property which appears in iterate_properties of the mapper? Cheers, M -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
Re: [sqlalchemy] association_proxy as property?
On Nov 16, 2010, at 11:14 AM, A.M. wrote: Hello, To generate json from our SQLAlchemy model objects, we are using iterate_properties to determine how to dictify the object. One of our objects uses association_proxy which we would like to represent in the JSON. Unfortunately, because it is not a property, the dictification misses this property. I feel like I am missing something simple here. How can I make an association_proxy appear to be a property which appears in iterate_properties of the mapper? 1. why not use dir(myobject) to get a view of your object as a whole ? 2. implicit conversion to JSON and such is a little sloppy. You'd be better off using a structured approach like Colander: http://docs.repoze.org/colander/ -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
Re: [sqlalchemy] association_proxy as property?
On Nov 16, 2010, at 11:43 AM, Michael Bayer wrote: On Nov 16, 2010, at 11:14 AM, A.M. wrote: Hello, To generate json from our SQLAlchemy model objects, we are using iterate_properties to determine how to dictify the object. One of our objects uses association_proxy which we would like to represent in the JSON. Unfortunately, because it is not a property, the dictification misses this property. I feel like I am missing something simple here. How can I make an association_proxy appear to be a property which appears in iterate_properties of the mapper? 1. why not use dir(myobject) to get a view of your object as a whole ? We swiped dictify from sprox.saormprovider: http://bitbucket.org/percious/sprox/src/tip/sprox/saormprovider.py#cl-321 We like the behavior that a REST call to retrieve an SQLAlchemy object returns pks for relationships (instead of loading the entire result hierarchy), so subsequent REST calls are required to dig deeper into the tree of results. Using dir() is definitely a good suggestion which I will try. You are probably right that we are using iterate_properties improperly. 2. implicit conversion to JSON and such is a little sloppy. You'd be better off using a structured approach like Colander: http://docs.repoze.org/colander/ It looks like I would have to either re-define all objects using the Colander syntax or implement a method which converts existing SQLAlchemy models to Colander schema objects. Even if the latter function already exists, I still have the problem of determining automatically which properties to encode, no? Cheers, M -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
Re: [sqlalchemy] association_proxy as property?
On Tue, Nov 16, 2010 at 9:05 AM, A.M. age...@themactionfaction.com wrote: On Nov 16, 2010, at 11:43 AM, Michael Bayer wrote: On Nov 16, 2010, at 11:14 AM, A.M. wrote: To generate json from our SQLAlchemy model objects, we are using iterate_properties to determine how to dictify the object. One of our objects uses association_proxy which we would like to represent in the JSON. Unfortunately, because it is not a property, the dictification misses this property. I feel like I am missing something simple here. How can I make an association_proxy appear to be a property which appears in iterate_properties of the mapper? 2. implicit conversion to JSON and such is a little sloppy. You'd be better off using a structured approach like Colander: http://docs.repoze.org/colander/ It looks like I would have to either re-define all objects using the Colander syntax or implement a method which converts existing SQLAlchemy models to Colander schema objects. Even if the latter function already exists, I still have the problem of determining automatically which properties to encode, no? You may find you'll need to do even further work to determine which properties to encode. I do the same (using Flatland for serialization), and part of that challenge was determining where the edges of the business objects were. (If you have relations, maybe some of them are part of the object (as user's email addresses) and some of them aren't (a User-Users list of the user's friends). In the end I went with a combination of class annotation and heuristics based on iterating mapper properties. This allowed me to traverse the mappings to reliably find the edges and also include the occasional transient attribute or other oddball that needed to be in the serialized form. -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
Re: [sqlalchemy] association_proxy as property?
On Nov 16, 2010, at 12:05 PM, A.M. wrote: 2. implicit conversion to JSON and such is a little sloppy. You'd be better off using a structured approach like Colander: http://docs.repoze.org/colander/ It looks like I would have to either re-define all objects using the Colander syntax or implement a method which converts existing SQLAlchemy models to Colander schema objects. Even if the latter function already exists, I still have the problem of determining automatically which properties to encode, no? Jek's suggestion is good here, also in my experience when I need to use JSON for something, it implies I'm communicating with some other system that doesn't know about my mapped objects - meaning, even if the JSON structure is initially driven by the ORM completely, I need the JSON structure to remain independent of changes in the ORM model in any case. But usually I'm dealing with a service that looks dramatically different from my ORM models anyway. Its again the same dichotomy in SQLAlchemy itself, your json messages are not your domain objects ;) I haven't used Colander and instead have something homegrown - a core feature is that it maintains a mapping of object attributes, in some cases dot-separated paths, to field names that would be generated in JSON or XML. I also use it to translate against .csv and .xls formats. Most apps I work on end up that way, so I go straight to explicit mappings up front since I know the variability is going to be great. -- You received this message because you are subscribed to the Google Groups sqlalchemy group. To post to this group, send email to sqlalch...@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
