Adds documentation for overriding default serializer based on conditions

[cgmckeever]

Purpose

Conversation on 'dynamic serializers' spawned an interesting solution via @groyoh
Just documenting it here as its a 💯 #protip

Changes

Updated serializer docs

Related GitHub issues

#1719

[cgmckeever]

wording welcome!

[groyoh]

@cgmckeever thanks for this PR! 💯

[cgmckeever]

@groyoh much better suggestion - updated

[NullVoxPopuli]

This is super handy to document!

[NullVoxPopuli]

LGTM

[cgmckeever]

@NullVoxPopuli added

[NullVoxPopuli]

wooooo

[KevinColemanInc]

edit: the issue is we are on v0.8.3. oops

@groyoh hey! so I don't think this documentation is correct. I tried implementing this and it doesn't seem to have the desired effect.

class MySerializer < ActiveModel::Serializer
  def self.serializer_for(model, options)

Override the serializer_for method on MySerializer doesn't do anything, because the code always uses the definition of serializer_for in ActiveModel::Serializer not whatever model itself is referencing.

active_model_serializers/lib/active_model_serializers/serializable_resource.rb

Line 57 in aad7779

@serializer ||= ActiveModel::Serializer.serializer_for(resource)

So I think the way it is currently structured, it is impossible to have custom serializers for polymorphic associations in a given parent serializer.

edit: I spoke too soon... so I guess it should be using the calling class's definition of serializer_for:

active_model_serializers/lib/active_model/serializer/reflection.rb

Line 98 in db87f8d

serializer_class = subject.class.serializer_for(association_value, reflection_options)

but I am still not able to get the described behavior...