Deferred defaults for Dash

[bradgessler]

Its desirable to have Procs that populate a default value for a key in Dash. Consider a key that generates a GUID and/or populates created_at may be wanted for an object:

class DeferredTest < Hashie::Dash
  property :created_at, :default => Proc.new{ Time.now }
  property :guid, :default => Proc.new{ rand(10000) } # Crappy GUID, I know...
end

This pull request adds support for lazily evaluated defaults to Dash to support this use case.

[ChristianPeters]

+1 Please merge this Pull Request!

Another important use case is (lazy) dynamic method invocation:

MyDash.property :width, default: proc { default_width }

def default_width
  # ...
end

[xavierdutreilh]

+1 deferred defaults would be an awesome feature for Dash.

[pdf]

Would most definitely like this merged...

[jch]

How do you feel about changing this to value.is_a? Proc? It's unlikely that users will assign an object that responds to call accidentally, but it'd be very unexpected behavior. A contrived example would be defaulting a middleware class as a value. In console, it looks like Proc.new, proc {...} and lambda {...} all return things that are Proc objects.

[jch]

Thanks for building out this useful feature! I'm going through an cleaning out issues and pulls and would love to merge this. Could you look over the comments I made and see if they're reasonable?

[bradgessler]

Fixed everything per everybody's comments.

[jch]

🤘