我很迷惑.我尝试使用print,但我知道人们适用putStrLn.它们之间有什么真正的区别？
print $ function
putStrLn $ function
我是Haskell的新手,我注意到@在阅读代码时有特定的作用,有人知道究竟做了什么？
添加gem和bundle安装后,我试图生成回形针,但是我收到错误？
在GemFile中
gem "paperclip", "~> 4.1"
在命令行中:
$ rails generate paperclip user avatar
我得到的错误:
/Users/amirna/.rvm/gems/ruby-2.1.1/gems/railties-4.1.0/lib/rails/generators/actions/create_migration.rb:13:in `migration_file_name': protected method `migration_file_name' called for #<PaperclipGenerator:0x007fc6c7e43690> (NoMethodError)
from /Users/amirna/.rvm/gems/ruby-2.1.1/gems/railties-4.1.0/lib/rails/generators/actions/create_migration.rb:34:in `existing_migration'
from /Users/amirna/.rvm/gems/ruby-2.1.1/gems/thor-0.19.1/lib/thor/actions/empty_directory.rb:112:in `invoke_with_conflict_check'
from /Users/amirna/.rvm/gems/ruby-2.1.1/gems/thor-0.19.1/lib/thor/actions/create_file.rb:60:in `invoke!'