How to denote associations in V2

[jhollinger]

V1 has just association for both singular and multiple associations, and we fuzzily figure out which at runtime. V2 (release-2.0 branch) currently splits it into two DSL methods: object for singular and collection for multiple (terms up for debate). This has some pros, but one big con is the added difficulty in updating Blueprints from V1 to V2.

Here are all the options I can think of.

# Option 1 (explicit)
object :category, CategoryBlueprint
collection :parts, PartBlueprint

# Option 2 (explicit)
association :category, CategoryBlueprint
association :parts, [PartBlueprint]

# Option 3 (dynamic)
association :category, CategoryBlueprint
association :parts, PartBlueprint

# Option 4 (dynamic AND explicit)
association :category, CategoryBlueprint # dynamic
object :category, CategoryBlueprint
collection :parts, PartBlueprint

# Option 4a (dynamic AND explicit)
association :category, CategoryBlueprint # dynamic
association :category, CategoryBlueprint, singular: true
association :parts, PartBlueprint, collection: true

Explicit

Pros:

• Explicit - no runtime guessing of singular vs multiple
• Allows separate extractor methods for singular and multiple
• Allows for more targeted Blueprint/view-wide options (e.g. object_default, collection_default, collection_default_if, etc)
• Allows for more targeted hooks (e.g. object_value, collection_value)

Cons:

• Upgrading to V2 requires more changes

Dynamic

Pros:

• Fewer changes when updating

Cons:

• Singular and collection use same extractor method
• Fewer targeted options
• Fewer targeted hooks