Question

所以，让我说我想在ActiveRecord范围内检查nils：

public class CommandService : ICommandService
{
    private readonly IEnumerable<ICommandHandler> _commandHandlers; 
    private readonly ISerializationFormatter _formatter;

    public CommandService(IEnumerable<ICommandHandler> commandHandlers,
        ISerializationFormatter formatter)
    {
        _commandHandlers = commandHandlers;
        _formatter = formatter;
    }

    public void Execute(string command)
    {
        if (command == null)
            throw new ArgumentNullException("command");

        var request = _formatter.Deserialize<CommandRequest>(command);

        var handler = _commandHandlers
            .Single(x => x.CommandType == request.Command.GetType());

        handler.Handle(request.Command);
    }
}

private void ConfigureContainer(Container container)
{
    container.Register(typeof(ICommandHandler<>),new[] { typeof(BusinessLayer).Assembly });

    container.RegisterDecorator(typeof(ICommandHandler<>),
        typeof(WeaklyTypedCommandHandler<>));

    //container.RegisterCollection<ICommandHandler>????
}

Answer 1

您可以返回self来返回默认范围：

class Person < ActiveRecord::Base

  def self.closest(point = nil)
    point.nil? ? self : where(point: point)
  end

end

Answer 2

修改/溶液

正如上面的评论所述，正如@ahmacleod指出的那样，all正是我们正在寻找的

scope :closest, ->(point) { point.nil? ? all : where(point: point) }

结束修改

~~我想我找到了我要找的东西，它是unscoped~~

scope :closest, ->(point) { point.nil? ? unscoped : where(point: point) }

问题在于，如果我将其链接起来，如果我在它们之后使用它，我将失去先前的范围。

Answer 3

您可以将point参数设置为可选。像这样：

scope :closest, -> (point = '') {
  where(point: point)     
}

这样，范围每次都会返回一个ActiveRecord :: Relation。

希望这有帮助：）

ActiveRecord范围＆＃34;默认＆＃34;结果

3 个答案: