I'm using DataMapper 1.2.0 and trying to define a custom property type to save in the database. I'm trying to understand how I'm supposed to do this, but I keep getting a NoMethodError
.
The object is a Dog
, but this type comes from a gem I don't control so I can't make it inherit from DataMapper::Property::Object
, so I think I need to create a new type which will be the custom property(DatabaseDog
). My understanding from the documentation is that it needs two methods:
#load(value)
takes a string from the database and returns the Dog
it represents#dump(value)
takes a Dog
and returns a string that will be persisted in the databaseThe fact that I keep getting an error makes me think I'm misunderstanding this.
How should I create this custom type properly?
Edit: I changed the dump method a bit and found it keeps receiving a string. Why is #dump
receiving a string as an argument? Shouldn't it be receiving the Dog
object that I'm assigning?
# The setup
require 'dm-core'
require 'dm-migrations'
require 'dm-sqlite-adapter'
class Dog
attr_accessor :name
end
class DatabaseDog < DataMapper::Property::Text
def load(value)
d = Dog.new
d.name = value
d
end
def dump(value)
puts "got here: #{value.inspect}"
if value.nil?
value
else
value.name
end
end
end
class User
include DataMapper::Resource
property :id, Serial, key: true
property :pet, DatabaseDog
end
DataMapper.setup(:default, "sqlite3://#{File.join(Dir.pwd, "users.db")}")
DataMapper.finalize
DataMapper.auto_upgrade!
# Finally, the test
ein = Dog.new
ein.name = "Ein"
spike = User.create
spike.pet = ein
spike.save #=> NoMethodError
got here: nil
got here: "#<Dog:0x007fca399b7d40>"
./test.rb:19:in `dump': undefined method `name' for "#<Dog:0x007fba19960c00>":String (NoMethodError)
from (...)/test/.bundle/gems/dm-core-1.2.0/lib/dm-core/property.rb:700:in `valid?'
from (...)/test/.bundle/gems/dm-core-1.2.0/lib/dm-core/resource/persistence_state/dirty.rb:88:in `block in valid_attributes?'
from (...)/test/.bundle/gems/dm-core-1.2.0/lib/dm-core/resource/persistence_state/dirty.rb:87:in `each_key'
from (...)/test/.bundle/gems/dm-core-1.2.0/lib/dm-core/resource/persistence_state/dirty.rb:87:in `valid_attributes?'
from (...)/test/.bundle/gems/dm-core-1.2.0/lib/dm-core/resource/persistence_state/dirty.rb:21:in `commit'
from (...)/test/.bundle/gems/dm-core-1.2.0/lib/dm-core/resource.rb:956:in `_persist'
from (...)/test/.bundle/gems/dm-core-1.2.0/lib/dm-core/resource.rb:987:in `block in update_with_hooks'
from (...)/test/.bundle/gems/dm-core-1.2.0/lib/dm-core/resource.rb:984:in `catch'
from (...)/test/.bundle/gems/dm-core-1.2.0/lib/dm-core/resource.rb:984:in `update_with_hooks'
from (...)/test/.bundle/gems/dm-core-1.2.0/lib/dm-core/resource.rb:1021:in `save_self'
from (...)/test/.bundle/gems/dm-core-1.2.0/lib/dm-core/resource.rb:1006:in `block in _save'
from (...)/test/.bundle/gems/dm-core-1.2.0/lib/dm-core/resource.rb:1222:in `run_once'
from (...)/test/.bundle/gems/dm-core-1.2.0/lib/dm-core/resource.rb:1005:in `_save'
from (...)/test/.bundle/gems/dm-core-1.2.0/lib/dm-core/resource.rb:405:in `save'
from ./test.rb:42:in `<main>'
According to the documentation DatabaseDog should inherit from DataMapper::Property::Object instead of DataMapper::Property::Text.