ruby – LoadError：没有这样的文件加载 – dm-sqlite-adapter

以下是我的Sinatra App的代码：

require 'rubygems'
require 'sinatra'
require 'dm-core'
require 'dm-timestamps'
# Also tried require 'datamapper',but the same issue shows up

DataMapper::setup(:default,"sqlite3://#{Dir.pwd}/raffle.db")

class Raffle 
    include DataMapper::Resource

    property :id,Serial
    property :firstName,String
    property :lastName,String
    property :email,String
    property :created_at,DateTime

end

# Create,upgrade,or migrate DB Tables
DataMapper.auto_upgrade!

我有宝石安装,作为宝石列表输出：

*** LOCAL GEMS ***

activemodel (3.0.9,3.0.3)
activerecord (3.0.9,3.0.3)
activesupport (3.0.9,3.0.3)
addressable (2.2.6)
arel (2.0.10,2.0.4)
bcrypt-ruby (2.1.4)
builder (2.1.2)
bundler (1.0.15)
data_objects (0.10.6)
datamapper (1.1.0)
diff-lcs (1.1.2)
dm-aggregates (1.1.0)
dm-constraints (1.1.0)
dm-core (1.1.0)
dm-migrations (1.1.0)
dm-serializer (1.1.0)
dm-timestamps (1.1.0)
dm-transactions (1.1.0)
dm-types (1.1.0)
dm-validations (1.1.0)
do_sqlite3 (0.10.6)
fastercsv (1.5.4)
ffi (0.6.3)
i18n (0.5.0,0.4.2)
json (1.5.3,1.4.6)
mime-types (1.16)
rack (1.3.0,1.2.1)
rack-test (0.5.6)
rake (0.8.7)
require_all (1.2.0)
rspec (2.6.0)
rspec-core (2.6.4)
rspec-expectations (2.6.0)
rspec-mocks (2.6.0)
shotgun (0.9)
sinatra (1.2.6,1.1.0)
sqlite3 (0.1.1)
stringex (1.2.1)
tilt (1.3.2,1.1)
typhoeus (0.2.4,0.2.0)
tzinfo (0.3.29,0.3.23)
uuidtools (2.1.2)

任何建议/洞察总是赞赏.