我已经成功创建了一个数据库并使用以下方式执行了我的第一次迁移：
class CreateUsers < ActiveRecord::Migration
def change
create_table :users do |t|
t.string :name
t.string :email
t.timestamps
end
end
end
当我尝试重置数据库时，我得到以下内容：
rake aborted!
can't convert nil into String
我不确定导致此问题的原因或如何调试，以便提供任何帮助。
我正在运行Rails 3.1
错误的完整痕迹是：
** Invoke db:reset (first_time)
** Invoke db:drop (first_time)
** Invoke db:load_config (first_time)
** Invoke rails_env (first_time)
** Execute rails_env
** Execute db:load_config
** Execute db:drop
** Invoke db:setup (first_time)
** Invoke db:create (first_time)
** Invoke db:load_config
** Execute db:create
db/test.sqlite3 already exists
** Invoke db:schema:load (first_time)
** Invoke environment (first_time)
** Execute environment
** Execute db:schema:load
-- create_table("users", {:force=>true})
-> 0.0050s
-- initialize_schema_migrations_table()
-> 0.0053s
-- assume_migrated_upto_version(20111212200427, ["/Users/xxxx/My_Work/Resources/Rails/Books/Rails-Tutorial/Sample-App/sample_app/db/migrate"])
-> 0.0055s
** Invoke db:seed (first_time)
** Invoke db:abort_if_pending_migrations (first_time)
** Invoke environment
** Execute db:abort_if_pending_migrations
** Execute db:seed
rake aborted!
can't convert nil into String
/Users/xxxx/.rvm/gems/ruby-1.9.3-p0/gems/railties-3.1.0/lib/rails/engine.rb:487:in `exist?'
/Users/xxxx/.rvm/gems/ruby-1.9.3-p0/gems/railties-3.1.0/lib/rails/engine.rb:487:in `load_seed'
/Users/xxxx/.rvm/gems/ruby-1.9.3-p0/gems/activerecord-3.1.0/lib/active_record/railties/databases.rake:299:in `block (2 levels) in <top (required)>'
/Users/xxxx/.rvm/gems/ruby-1.9.3-p0/gems/rake-0.9.2.2/lib/rake/task.rb:205:in `call'
/Users/xxxx/.rvm/gems/ruby-1.9.3-p0/gems/rake-0.9.2.2/lib/rake/task.rb:205:in `block in execute'
/Users/xxxx/.rvm/gems/ruby-1.9.3-p0/gems/rake-0.9.2.2/lib/rake/task.rb:200:in `each'
/Users/xxxx/.rvm/gems/ruby-1.9.3-p0/gems/rake-0.9.2.2/lib/rake/task.rb:200:in `execute'
/Users/xxxx/.rvm/gems/ruby-1.9.3-p0/gems/rake-0.9.2.2/lib/rake/task.rb:158:in `block in invoke_with_call_chain'
/Users/xxxx/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/1.9.1/monitor.rb:211:in `mon_synchronize'
/Users/xxxx/.rvm/gems/ruby-1.9.3-p0/gems/rake-0.9.2.2/lib/rake/task.rb:151:in `invoke_with_call_chain'
/Users/xxxx/.rvm/gems/ruby-1.9.3-p0/gems/rake-0.9.2.2/lib/rake/task.rb:176:in `block in invoke_prerequisites'
/Users/xxxx/.rvm/gems/ruby-1.9.3-p0/gems/rake-0.9.2.2/lib/rake/task.rb:174:in `each'
/Users/xxxx/.rvm/gems/ruby-1.9.3-p0/gems/rake-0.9.2.2/lib/rake/task.rb:174:in `invoke_prerequisites'
/Users/xxxx/.rvm/gems/ruby-1.9.3-p0/gems/rake-0.9.2.2/lib/rake/task.rb:157:in `block in invoke_with_call_chain'
/Users/xxxx/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/1.9.1/monitor.rb:211:in `mon_synchronize'
/Users/xxxx/.rvm/gems/ruby-1.9.3-p0/gems/rake-0.9.2.2/lib/rake/task.rb:151:in `invoke_with_call_chain'
/Users/xxxx/.rvm/gems/ruby-1.9.3-p0/gems/rake-0.9.2.2/lib/rake/task.rb:176:in `block in invoke_prerequisites'
/Users/xxxx/.rvm/gems/ruby-1.9.3-p0/gems/rake-0.9.2.2/lib/rake/task.rb:174:in `each'
/Users/xxxx/.rvm/gems/ruby-1.9.3-p0/gems/rake-0.9.2.2/lib/rake/task.rb:174:in `invoke_prerequisites'
/Users/xxxx/.rvm/gems/ruby-1.9.3-p0/gems/rake-0.9.2.2/lib/rake/task.rb:157:in `block in invoke_with_call_chain'
/Users/xxxx/.rvm/rubies/ruby-1.9.3-p0/lib/ruby/1.9.1/monitor.rb:211:in `mon_synchronize'
/Users/xxxx/.rvm/gems/ruby-1.9.3-p0/gems/rake-0.9.2.2/lib/rake/task.rb:151:in `invoke_with_call_chain'
/Users/xxxx/.rvm/gems/ruby-1.9.3-p0/gems/rake-0.9.2.2/lib/rake/task.rb:144:in `invoke'
/Users/xxxx/.rvm/gems/ruby-1.9.3-p0/gems/rake-0.9.2.2/lib/rake/application.rb:116:in `invoke_task'
/Users/xxxx/.rvm/gems/ruby-1.9.3-p0/gems/rake-0.9.2.2/lib/rake/application.rb:94:in `block (2 levels) in top_level'
/Users/xxxx/.rvm/gems/ruby-1.9.3-p0/gems/rake-0.9.2.2/lib/rake/application.rb:94:in `each'
/Users/xxxx/.rvm/gems/ruby-1.9.3-p0/gems/rake-0.9.2.2/lib/rake/application.rb:94:in `block in top_level'
/Users/xxxx/.rvm/gems/ruby-1.9.3-p0/gems/rake-0.9.2.2/lib/rake/application.rb:133:in `standard_exception_handling'
/Users/xxxx/.rvm/gems/ruby-1.9.3-p0/gems/rake-0.9.2.2/lib/rake/application.rb:88:in `top_level'
/Users/xxxx/.rvm/gems/ruby-1.9.3-p0/gems/rake-0.9.2.2/lib/rake/application.rb:66:in `block in run'
/Users/xxxx/.rvm/gems/ruby-1.9.3-p0/gems/rake-0.9.2.2/lib/rake/application.rb:133:in `standard_exception_handling'
/Users/xxxx/.rvm/gems/ruby-1.9.3-p0/gems/rake-0.9.2.2/lib/rake/application.rb:63:in `run'
/Users/xxxx/.rvm/gems/ruby-1.9.3-p0/gems/rake-0.9.2.2/bin/rake:33:in `<top (required)>'
/Users/xxxx/.rvm/gems/ruby-1.9.3-p0/bin/rake:19:in `load'
/Users/xxxx/.rvm/gems/ruby-1.9.3-p0/bin/rake:19:in `<main>'
Tasks: TOP => db:reset => db:setup => db:seed