String/Lambda support for conditional attributes/associations

[mtsmfm]

Purpose

I want to exclude attribute if its association/attribute is nil.

:if option accepts only symbol at this time so we must write condition like following:

class UserSerializer < ApplicationSerializer
  has_one :game, if: :game_exists?

  def game_exists?
    object.game
  end
end

But it is not bad to support String like rails:

class UserSerializer < ApplicationSerializer
  has_one :game, if: 'object.game'
end

I don't have any use case for lambda(proc) at this time but many developers who experienced rails will guess that it accepts lambda.

Related GitHub issues

#1403

[beauby]

Yeah, I had support for lambda in mind when adding this feature, so 👍 on the idea of this PR.

[beauby]

I'm not sure building a throwaway lambda here is the best way. How about the following

def condition_lambda(serializer)
  case condition
  when Symbol
    serializer.public_send(condition)
  when String
    serializer.instance_eval(condition)
  when Proc
    condition.call(serializer)
...

[mtsmfm]

Yeah, it can be a method 👍
Fixed and force pushed 😄

[beauby]

LGTM – I'll merge unless somebody raises concerns.
Would you mind adding corresponding docs for the feature?

[bf4]

would be good to include a message here

[mtsmfm]

👍

By the way, it is better if raise an error on evaluate serializer's DSL I think.

https://github.com/rails-api/active_model_serializers/pull/1699/files#diff-689b80d81fb899042cc36668903c9a3dR10

[mtsmfm]

Hmm, tests for jruby-9.0.4.0 on appveyor are failed but passed on travis 😕

[beauby]

@mtsmfm Looking into the appveyor thing.

[mtsmfm]

@beauby I noticed appveyor setting for JRuby is wrong and fixed (b33791b
)

[beauby]

@mtsmfm Awesome! Would you mind submitting the AppVeyor settings fix as a separate PR?

[beauby]

Could you rebase?

[mtsmfm]

rebased!

[nicolas-besnard]

This is great for one field, but what if I've a lot a field I wanted to hide ? Do I have to add a predicate after each attribute / association ?