Support model.from_json(JSON::Any)

[Blacksmoke16]

This PR resolves #170 by including support for model.new(JSON::Any)

I just added another layer of ternary that checks of the value is of the JSON::Any type, if it is then use the JSON::Any .as_x to cast it to proper type.

[Blacksmoke16]

Unfortunately this still does not work. might be able to create a wrapper function that will instantiate multiple classes and return an array of them to replicate the Array(Klass).from_json(ARRAY)

class Foo < Granite::Base
  adapter mysql
  table_name foos

  primary type_id : Int64, auto: false
  field capacity : Float32
end

  p Array(Foo).new(JSON.parse(%([{"type_id": 1, "capacity": 69.0},{"type_id": 2, "capacity": 5.0},{"type_id": 3, "capacity": 100.0}])))

Error in src/EveToolsApi.cr:72: no overload matches 'Array(Foo).new' with type JSON::Any
Overloads are:
 - Array(T).new(size : Int, value : T)
 - Array(T).new(ctx : YAML::ParseContext, node : YAML::Nodes::Node)
 - Array(T).new(initial_capacity : Int)
 - Array(T).new(pull : JSON::PullParser)
 - Array(T).new()
 - Array(T).new(ctx : YAML::ParseContext, node : YAML::Nodes::Node, &block)
 - Array(T).new(size : Int, &block)
 - Array(T).new(pull : JSON::PullParser, &block)

  p Array(Foo).new(JSON.parse(%([{"type_id": 1, "capacity": 69.0},{"type_id": 2, "capacity": 5.0},{"type_id": 3, "capacity": 100.0}])))

[Blacksmoke16]

I refactored things to support model.from_json instead of .new to keep inline with standard JSON.mapping usage.

This accounts for creating a single record from a json object, or an array of models from an array of json objects.

The one con of this is that the user has to specify which it is. For example see the spec:

https://github.com/Blacksmoke16/granite-orm/blob/a5108f266e6470c4cafa36425403631de6695863/spec/granite_spec.cr#L70-L97

Notice how in the first i am specifying .as(Review) and in the other i am specifying .as(Array(WebSite)). This isn't the end of the world imo but if anyone has a better idea on how to remove the need for that i would be happy to hear it.

[drujensen]

man, this is some true ugliness on my part. Maybe someday we can figure out how to clean this up.

[robacarp]

Nice addition. The json api isn't very elegant, and I think it's possible to come up with a better DSL than what from_json provides, but I don't think it's necessary for this addition to be helpful.

[Blacksmoke16]

@robacarp it should be clarified that the from_json implemented here is not the same one as Crystals Array(Model).from_json(json)

[robacarp]

@Blacksmoke16 yep. Since there are two approvals, are you ready for this to merge?

[Blacksmoke16]

I probably should add some info to the README. I'll do that tonight and can merge it tomorrow.

[drujensen]

@Blacksmoke16 let me know when you are ready.

[Blacksmoke16]

Readme is updated. Should be good to go @drujensen

[robacarp]

@Blacksmoke16 thank you!