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我正在关注 Ruby on Rails 指南，但遇到了使用 gem“Faker”生成虚假内容的问题。我安装了 faker 并按照说明将用户和照片填充到我的项目中。我在 lib/tasks/populate.rake 中创建了这个文件

lib/tasks/populate.rake

namespace :db do
  desc "Fill database with sample data"
  task populate: :environment do
    10.times do |n|
      puts "[DEBUG] creating user #{n+1} of 10"
      name = Faker::Name.name
      email =  "user-#{n+1}@example.com" 
      password = "password"
      User.create!( name: name,
                    email: email,
                    password: password,
                    password_confirmation: password)
    end

    User.all.each do |user|
      puts "[DEBUG] uploading images for user #{user.id} of #{User.last.id}"
      10.times do |n|
        image = File.open(Dir.glob(File.join(Rails.root, 'sampleimages', '*')).sample)
        description = %w(cool awesome crazy wow adorbs incredible).sample
        user.pins.create!(image: image, description: description)
      end
    end
  end
end

现在我要做的就是将“rake db:populate”放在我的终端（以及正确的文件夹中）。当我这样做时，我得到：

rake db:populate
[DEBUG] creating user 1 of 10
[DEBUG] creating user 2 of 10
[DEBUG] creating user 3 of 10
[DEBUG] creating user 4 of 10
[DEBUG] creating user 5 of 10
[DEBUG] creating user 6 of 10
[DEBUG] creating user 7 of 10
[DEBUG] creating user 8 of 10
[DEBUG] creating user 9 of 10
[DEBUG] creating user 10 of 10
[DEBUG] uploading images for user 15 of 25
rake aborted!
can't convert nil into String
/Users/ScottDAlessandro/code/omrails/lib/tasks/populate.rake:18:in `initialize'
/Users/ScottDAlessandro/code/omrails/lib/tasks/populate.rake:18:in `open'
/Users/ScottDAlessandro/code/omrails/lib/tasks/populate.rake:18:in `block (4 levels) in <top (required)>'
/Users/ScottDAlessandro/code/omrails/lib/tasks/populate.rake:17:in `times'
/Users/ScottDAlessandro/code/omrails/lib/tasks/populate.rake:17:in `block (3 levels) in <top (required)>'
/Users/ScottDAlessandro/code/omrails/lib/tasks/populate.rake:15:in `each'
/Users/ScottDAlessandro/code/omrails/lib/tasks/populate.rake:15:in `block (2 levels) in <top (required)>'
/usr/local/rvm/gems/ruby-1.9.3-p392/gems/rake-10.0.4/lib/rake/task.rb:246:in `call'
/usr/local/rvm/gems/ruby-1.9.3-p392/gems/rake-10.0.4/lib/rake/task.rb:246:in `block in execute'
/usr/local/rvm/gems/ruby-1.9.3-p392/gems/rake-10.0.4/lib/rake/task.rb:241:in `each'
/usr/local/rvm/gems/ruby-1.9.3-p392/gems/rake-10.0.4/lib/rake/task.rb:241:in `execute'
/usr/local/rvm/gems/ruby-1.9.3-p392/gems/rake-10.0.4/lib/rake/task.rb:184:in `block in invoke_with_call_chain'
/usr/local/rvm/gems/ruby-1.9.3-p392/gems/rake-10.0.4/lib/rake/task.rb:177:in `invoke_with_call_chain'
/usr/local/rvm/gems/ruby-1.9.3-p392/gems/rake-10.0.4/lib/rake/task.rb:170:in `invoke'
/usr/local/rvm/gems/ruby-1.9.3-p392/gems/rake-10.0.4/lib/rake/application.rb:143:in `invoke_task'
/usr/local/rvm/gems/ruby-1.9.3-p392/gems/rake-10.0.4/lib/rake/application.rb:101:in `block (2 levels) in top_level'
/usr/local/rvm/gems/ruby-1.9.3-p392/gems/rake-10.0.4/lib/rake/application.rb:101:in `each'
/usr/local/rvm/gems/ruby-1.9.3-p392/gems/rake-10.0.4/lib/rake/application.rb:101:in `block in top_level'
/usr/local/rvm/gems/ruby-1.9.3-p392/gems/rake-10.0.4/lib/rake/application.rb:110:in `run_with_threads'
/usr/local/rvm/gems/ruby-1.9.3-p392/gems/rake-10.0.4/lib/rake/application.rb:95:in `top_level'
/usr/local/rvm/gems/ruby-1.9.3-p392/gems/rake-10.0.4/lib/rake/application.rb:73:in `block in run'
/usr/local/rvm/gems/ruby-1.9.3-p392/gems/rake-10.0.4/lib/rake/application.rb:160:in `standard_exception_handling'
/usr/local/rvm/gems/ruby-1.9.3-p392/gems/rake-10.0.4/lib/rake/application.rb:70:in `run'
Tasks: TOP => db:populate
(See full trace by running task with --trace)

我最关心的是

“rake 中止！无法将 nil 转换为字符串”

它似乎创建了用户，但没有上传任何图片。

问题：

a) 为什么 rake 被中止？

b) 如何删除我创建的用户？我知道的唯一方法是“User.all”，然后是 User.delete（在此处输入一个数字）......有更有效的方法吗？

帮助将不胜感激:) 谢谢！

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1 回答 1

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你的<rails_root>/sampleimages目录是空的。Dir.glob(...)正在返回一个空数组，当您调用sample它时正在返回nil. 当你打电话时，File.open(nil)你会得到异常并 rake 中止。

如果你想删除用户表中的所有行，你可以这样做User.destroy_all。

于 2013-06-08T01:40:52.410 回答