I'm working on a Django app for keeping track of collections (coins, cards, gems, stamps, cars, whatever). You can have multiple collections, each collection can have sets (Pirates cards, Cardinals cards, etc.) and then of course the individual items in each collection/set. Each item can contain multiple pictures, a name, and description, but here's where I'm unsure how to proceed. Each collection will need it's own set of values, or fields, that the user will need to determine (condition, dimensions in the appropriate units, coin thickness, model number, etc). How can I make custom fields such that the user can name the field and choose the input type (text, numbers, dropdown w/choices) and those fields will show up to be entered on each item within that collection?
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1 Answers
This would be called an Entity-Attribute-Value (EAV) model and it is quite tricky to implement in the way you want. You have to anticipate all sorts of issues with user input, how to validate field types, what happens when the user wants to change fields, etc. I would start by reading the issues raised in that question and think about ways that you could modify your schema to avoid letting users define their own metadata at runtime. Are there some fields that could be common to all collections (like condition, dimensions, model number)? How tolerant do you want to be of data type issues, and will users be allowed to change field types after creation?
The more thought you put into implementation, the more issues you can avoid down the road.
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