Question

I’m working on a text game engine, and have run into a snag while developing the exploration module. When I try and instantiate my Location class with a block argument from a fixture, I’m getting this error:

ArgumentError, “wrong number of arguments (3 for 2)

for this code:

# in lib/explore/models/location.rb, line 15
class Location < RoundTable::Controllers::ActionDelegate
  # ... code omitted for brevity

  def initialize(slug, params = nil, &block)
    # ... code omitted for brevity

    if block_given?
      parser = Explore::Parsers::LocationParser.new(self)
      parser.instance_eval &block
    end # if
  end # constructor

  # ... code omitted for brevity
end # class Location

# in spec/fixtures/models/locations.rb, line 38
location :mushroom_kingdom, :name => "Mushroom Kingdom" do
  edges = Explore::Fixtures[:edges]
  edges.each do |key, value|
    go value.location, *value.params
  end # each
end # location

# in spec/models/location_spec.rb, line 193
context "initialized with block" do
  let :fixture do fixtures[:mushroom_kingdom] end

  subject { described_class.new fixture.slug, fixture.params, &fixture.block }

  it { puts subject.inspect }
end # context initialized with block

It’s pretty obviously a syntax error somewhere, where a block isn’t getting converted to a proc or vice versa, but I’ve been over the code a dozen times and can’t find it. If any eagle-eyed readers can help me out, I would be eternally grateful.

Source Files:

• location.rb (Github)
• location_spec.rb (Github)
• (fixtures) locations.rb (Github)

The full source is available on Github, but is split between two repositories:

• the engine (Github)
• the plugin (Github)

To run code or specs, the plugin code needs to be placed inside the engine directory in vendor/modules/plugins/explore.

Backtrace:

1) RoundTable::Vendor::Plugins::Explore::Models::Location initialization with block 
     Failure/Error: it { expect { described_class.new fixture.slug, fixture.params, &fixture.block }.not_to raise_error ArgumentError }
       expected no ArgumentError, got #<ArgumentError: wrong number of arguments (3 for 2)>
     # ./spec/models/location_spec.rb:33:in `block (4 levels) in <top (required)>'

2) RoundTable::Vendor::Plugins::Explore::Models::Location initialized with block 
     Failure/Error: subject { described_class.new fixture.slug, fixture.params, &fixture.block }
     ArgumentError:
       wrong number of arguments (3 for 2)
     # ./lib/explore/parsers/location_parser.rb:39:in `go'
     # ./spec/fixtures/models/locations.rb:41:in `block (2 levels) in <module:Models>'
     # ./spec/fixtures/models/locations.rb:40:in `each'
     # ./spec/fixtures/models/locations.rb:40:in `block in <module:Models>'
     # ./lib/explore/models/location.rb:49:in `instance_eval'
     # ./lib/explore/models/location.rb:49:in `initialize'
     # ./spec/models/location_spec.rb:196:in `new'
     # ./spec/models/location_spec.rb:196:in `block (3 levels) in <top (required)>'
     # ./spec/models/location_spec.rb:198:in `block (3 levels) in <top (required)>'

Edit 2012年06月06日:

• Replaced sample code with actual, non-conforming code
• Added links to full project

Answer 1

rspec sometimes swallows backtraces in ways that aren’t completely helpful (i think you can use the -b option to suppress this ) – the error is (I think) elsewhere.

From my reading of the code, mushroom kingdom’s block is instance_evaled on an instance of Explore::Parsers::LocationParser

This class defines a go method like so

def go(location, params = {})

but mushroom kingdom does

go value.location, *value.params

where value.params is the hash of options used to create an edge at the bottom of your edges fixtures file. In at least one case, that hash has 2 objects in it, so when you splat that you end up calling go with 3 arguments. Given that go appears to take a hash as its second argument, was that splat really intentional?