http://www.web2pyslices.com/main/slices/take_slice/85
On Mon, Dec 20, 2010 at 10:13 AM, Fabiano <[email protected]> wrote: > Hi, > > I am new to web2py and sure not if I am doing things the best way. I > am designing an app and would like your opinion on my choices and also > how could I implement some stuff in web2py. > > My problem: > > I have "classes of stuff" that I want to store on the database. > "Stuff" here is very generic and could be anything. (Not related to > OO, it is part of the problem I am modeling). > > The final end users of my app will be able to select a class to create > an "instance", by giving a name to it and selecting options for it. > > For each class I insert on my database I may have different options > available with different values. > > For example, I may have a class "person" with option "sex" with values > "male, female". A user may select this class "person" to create a > person, giving a name to it and selecting one value for its sex > option. > > I may have a class "Pie One" on my database, with an option "flavor" > with values "flavor 1, flavor 2, flavor 3" and another option "Fruit" > with values "apple, banana". > > I may have another class "Pie Two" also with an option "flavor" but > now with different available values for it: "flavor 2, flavor 4" an no > option "Fruit" now. > > When user chooses that it wants a "Pie One", he must also choose a > value for its "flavor", but only from available flavor for "Pie One", > and also must choose a value for its "fruit" option. > > If user wants a "Pie Two", the only option is "flavor", there is no > "fruit" nor "sex" option for this class. > > So far, we could have tables like this: > > > Stuff > id: name: > 1 'person' > 2 'pie one' > 3 'pie two' > > Option > id: name: > 1 'sex' > 2 'flavor' > 3 'fruit' > > OptionValue > id: option_id: name: > 1 1 'male' > 2 1 'female' > 3 2 'flavor 1' > 4 2 'flavor 2' > 5 2 'flavor 3' > 6 2 'flavor 4' > 7 3 'apple' > 8 3 'banana' > > StuffOption > stuff_id: option_value: > 1 1 > 1 2 > 2 3 > 2 4 > 2 5 > 2 7 > 2 8 > 3 4 > 3 6 > > From this, I can derive the option names available for each class by > its option values (values grouped by option names actually). > > When user will instantiate a class of "pie one", I want to show him a > field "flavor" with a dropdown box with available flavors for this > class, and another field "fruit" with fruits available for this class > in a dropdown box. I may have many options for each class (or none) > and the values available for the same option may be different in > different classes, so this has to be generic. How could I show these > dropdowns in web2py? > > > There is more. Each of theses classes will be classified in > categories, but each one may be in none or more than one category. > Also, when I display all classes of a category I must be able to > customize the order where the classes appear, and the order will be > independent for each category. I thought in implement this with > something like: > > Category > id: name: > 1 'people' > 2 'pies' > > StuffCategory > category_id: stuff_id: position: > 2 2 2 > 2 3 1 > > > > I would them retrieve items inverse ordered by position column, and > also set this column as autoincrement. This way, when I insert a new > class it will always show first on the list by default. If, lets say, > I want to insert an item on position 7, before insert it I would do: > "UPDATE StuffCategory SET position = position + 1 WHERE position >= 7" > and then insert it with its position = 7. > > It would be similar to move an class to a specific position, update > all position values between it and the desired position, before > setting the desired position. > > Would you guys say is this a good way to achieve this functionality or > is there a better way? Also, I don't want to write SQL directly, how > could I do this nicely in web2py? > > An additional interface I'd like to provide to admin to change the > order would be to list all classes in the right order, and in from of > each class, there would be two buttons: up and down arrows. clicking > on them would swap its position with the next record. I think this > would be great in an ajax interface, but I don't have a clue how to do > it in web2py yet. > > > And now, my last problem. Each of these classes will have a number of > images associated with them. One of the images of each class will be > its main image. Each value may have one of its image associate with it > also. > > For this, I may have an "Image" table: > > Image > id: stuff_id: image: > > And add a "main_image_id" column to stuff table. I thought of > "main_image" column be a reference to image table so it would be easy > to change the main image between the images available for that class. > > For the option values, I could add a column "image_id" also, where the > null value would be possible. > > My problems here are more about the interfaces for inserting new > stuff. How to put all this together. For example, I imagine the > following possibilities when admin is inserting new stuff to database: > > - The form for add new stuff and edit new stuff would be the same. > - This page would show all fields of stuff, and a list of all images > for it. > - Main image could be a radio button in front of the images, when the > admin inserts the first image for a stuff, it would be the main one. > - For the options, it would show a list of option values sorted by > option names. > - When adding a new option, it would show a list of all option values > in the database, sorted by options names. After selecting one, would > be possible to also select an image among the images for that stuff or > to upload a new one > > Again, no idea yet how I will glue all this together. I would like to > do this in the best web2py style, using SQL Forms for example, but I > am not sure yet if it will be possible, considering the complexity of > what I am aiming. > > I really would love your feedback on what I am doing, and nothing of > this is final yet, so if you think any of the things I wrote could be > done better in another way, please let me know. Later I won't be able > to change the design anymore. > > Kind regards, > Fabiano
