小编Dan*_*ier的帖子

我试图在FreeBSD上编译Echoprint codegen,但是失败了.但这里是我所得到的,当我尝试运行make或make install

> make
"Makefile", line 35: Missing dependency operator
"Makefile", line 39: Need an operator
"Makefile", line 41: Need an operator
"Makefile", line 50: warning: duplicate script for target "%.o" ignored
"Makefile", line 53: warning: duplicate script for target "%.o" ignored
"Makefile", line 56: warning: duplicate script for target "%.o" ignored
"Makefile", line 61: Missing dependency operator
"Makefile", line 62: warning: duplicate script for target "ifeq" ignored
"Makefile", line 62: warning: duplicate script for target "(,Darwin)" …

每个人都说模式匹配是函数式语言的一个很好的特性.为什么？

我不能简单地使用ifs和切换案例的一切吗？

我想了解使用模式匹配而不是常规过程编程ifs和switch case的优点

我正在使用Rails 4.1枚举字段

class User
    enum category: [ :client, :seller, :provider ]
end

当用户注册时,他从选择框中选择他的类别.默认为空,因为我想强制用户选择一个选项.

如果用户没有选择任何选项,我想返回带有验证消息的表单.这是注册表单中的选择框代码

    <%= f.select :category, [], {}, class: "form-control" do  %>
        <option value="99">Choose an option</option>

        <% User.categories.each do |cat,code| %>
            <option value="<%= code %>" <% if params["user"] && code.to_s == params["user"]["category"] %>selected='selected'<%end%> ><%= t(cat) %></option>
        <% end %>
    <% end %>

当控制器创建用户时,它不会向记录添加验证错误,而是引发异常.怎么避免这个？

ArgumentError - '99' is not a valid category:
  (gem) activerecord-4.1.1/lib/active_record/enum.rb:103:in `block (3 levels) in enum'
  (gem) activerecord-4.1.1/lib/active_record/attribute_assignment.rb:45:in `_assign_attribute'
  (gem) activerecord-4.1.1/lib/active_record/attribute_assignment.rb:32:in `block in assign_attributes

我有一个向自己发送消息的akka​​ actor:

  def receive = {
    while (...) {
       self ! "some message"
    }
  }

我想使用Throttler来控制此actor发送给自己的消息流.

  val throttler = system.actorOf(Props(new TimerBasedThrottler(15 msgsPer (1.minute))))
  throttler ! SetTarget(Some(self))

然后更改while循环以向throttler发送消息:

    while (...) {
       throttler ! "some message"
    }

问题是我不知道如何从actor内部访问"系统",以创建节流器.这该怎么做？有没有更好的方法？

我知道有一些Java的ActiveResource 客户端库,比如RAPA和JactiveResource

问题是:有没有简单的方法在Java中创建ActiveResource 的服务器端？

在RubyOnRails中,您需要做的就是使用Inherited Resources gem.Java中有类似的东西吗？

什么是Ruby最好的Twitter API库？

我想做一些简单的事情,比如:

• 搜索日期范围的细节关键字
• 开始关注人
• 推特消息

如何使用您推荐的库来完成这些操作？

我想从AWS EC2控制面板运行Ubuntu GPU实例,但组合框没有要选择的g2.2xlarge选项.看起来GPU实例仅适用于Amazon AMI.当我选择Ubuntu时,它不会列出GPU.有没有办法使它工作？

我在Scala中有一个类型:

  type Fingerprint = Seq[(Int, Int)]

我想覆盖toString这种类型.我怎样才能做到这一点？

我有一个这样的简单形式:

<form name="serachForm" method="post" action="/home/search">   
  <input type="text" name="searchText" size="15" value="">
  <input class="image" name="searchsubmit" value="Busca" src="/images/btn_go_search.gif" align="top" border="0" height="17" type="image" width="29">
</form>

和这种方法的控制器:

  def busca
    puts params[:searchText]
  end

当我单击表单中的图像按钮时,我得到一个ActionController :: InvalidAuthenticityToken.这是完整的StackTrace:

/Library/Ruby/Gems/1.8/gems/actionpack-2.2.2/lib/action_controller/request_forgery_protection.rb:86:in verify_authenticity_token' /Library/Ruby/Gems/1.8/gems/activesupport-2.2.2/lib/active_support/callbacks.rb:178:in send'/Library/Ruby/Gems/1.8/gems/activesupport-2.2.2/lib/active_support /callbacks.rb:178:in evaluate_method' /Library/Ruby/Gems/1.8/gems/activesupport-2.2.2/lib/active_support/callbacks.rb:166:in 调用'/Library/Ruby/Gems/1.8/gems/actionpack-2.2.2/lib/action_controller/filters.rb:225:in call' /Library/Ruby/Gems/1.8/gems/actionpack-2.2.2/lib/action_controller/filters.rb:629:in run_before_filters'/ Library /Ruby/Gems/1.8 / gems /actionpack-2.2.2/lib/action_controller/filters.rb:615:in call_filters' /Library/Ruby/Gems/1.8/gems/actionpack-2.2.2/lib/action_controller/filters.rb:610:in perform_action_without_benchmark'/ Library/Ruby/Gems/1.8/gems/actionpack-2.2.2/lib/action_controller / benchmarking.rb:68:in perform_action_without_rescue' /Library/Ruby/Gems/1.8/gems/actionpack-2.2.2/lib/action_controller/benchmarking.rb:68:in perform_action_without_rescue' /Library/Ruby/Gems/1.8/gems/actionpack-2.2.2/lib/action_controller/rescue.rb:136:in perform_action_without_caching' /Library/Ruby/Gems/1.8/gems/actionpack-2.2.2/lib/action_controller/caching/sql_cache.rb:13:inperform_action'/ Library/Ruby/Gems/1.8/gems/activerecord-2.2.2/lib/active_record/connection_adapters/abstract/query_cache.rb:34:in cache' /Library/Ruby/Gems/1.8/gems/activerecord-2.2.2/lib/active_record/query_cache.rb:8:in cache'/ Library/Ruby/Gems/1.8/gems/actionpack -2.2 .2/lib/action_controller/caching/sql_cache.rb:12:in perform_action' /Library/Ruby/Gems/1.8/gems/actionpack-2.2.2/lib/action_controller/base.rb:524:in send process_without_filters' /Library/Ruby/Gems/1.8/gems/actionpack-2.2.2/lib/action_controller/filters.rb:606:in '/Library /Ruby/Gems/1.8/gems/actionpack-2.2.2/lib/action_controller/base.rb:524:in process_without_session_management_support'/ Library /Ruby/Gems/1.8/gems/actionpack-2.2.2/lib/action_controller/session_management.rb:134:in process' /Library/Ruby/Gems/1.8/gems/actionpack-2.2.2/lib/action_controller/base.rb:392:in process'/ Library/Ruby/Gems/1.8/gems/rails-2.2.2/lib/webrick_server.rb …

我在Interbase中有一个数据库,我想使用ActiveRecord直接从我的Rails应用程序访问它.我该怎么做？