Question

我有一个方法如下......

async

我一直收到错误＆＃34;错误的参数数量（0表示1）＆＃34;在＆＃34;采取＆＃34;线。我使用rails 4.0.1是导致问题还是我错过了什么？

编辑查看4.0.1 http://rails.documentation.codyrobbins.com/4.0.10/classes/ActiveRecord/FinderMethods.html#method-i-take

的文档

我将方法更新为

using System;
using System.Windows;
using System.Net.Http;
using System.Threading;
using System.Threading.Tasks;
using System.Collections.Generic;
using System.Collections.Concurrent;

// sample stock quote project implementing multiple async Tasks
// and various Dictionary objects to store results
namespace QuoteServer
{
    public partial class MainWindow : Window
    {
        // quote web service root Url
        private const string _baseUrl = @"http://finance.yahoo.com/d/quotes.csv?f=l1&s=";

        /// <summary>
        /// Sample List of 30 Stock Symbols (Dow Jones Industrial Average) 
        /// </summary>
        List<string> ListDJIA = new List<string>
        {
            "AAPL", "AXP",  "BA",   "CAT",  "CSCO", "CVX",  "DD",   "DIS",  "GE",   "GS",
            "HD",   "IBM",  "INTC", "JNJ",  "JPM",  "KO",   "MCD",  "MMM",  "MRK",  "MSFT",
            "NKE",  "PFE",  "PG",   "TRV",  "UNH",  "UTX",  "V",    "VZ",   "WMT",  "XOM"
        };

        // store results (multiple stock Px) of asynchronous Tasks in various Dictionary objects
        private Dictionary<string, double> _dQuote = new Dictionary<string,double>();
        private ConcurrentDictionary<string, double> _cdQuote = new ConcurrentDictionary<string,double>();
        private SortedDictionary<string, double> _sdQuote = new SortedDictionary<string,double>();

        private CancellationTokenSource _CTS;

        public MainWindow(){ InitializeComponent();}

        /// <summary>start multiple async Tasks to get quote list</summary>
        private async void startButton_Click(object sender, RoutedEventArgs e) {
            _CTS = new CancellationTokenSource();
            try{
                await AccessWebAsync(_CTS.Token);
                resultsTextBox.Text += "\r\nDownloads complete.";
            }
            catch (OperationCanceledException){
                resultsTextBox.Text += "\r\nDownloads canceled.\r\n";
            }
            catch { resultsTextBox.Text += "\r\nDownloads failed.\r\n"; }
            finally { _CTS = null; }
        }

        /// <summary>cancel async Tasks</summary>
        private void cancelButton_Click(object sender, RoutedEventArgs e) {
            if (_CTS != null) _CTS.Cancel();
         }

        /// <summary>
        /// access web service in async mode to run multiple Tasks
        /// </summary>
        /// <param name="CT">CancellationToken</param>
        /// <returns>Task</returns>
        async Task AccessWebAsync(CancellationToken CT)
        {
            _dQuote.Clear();
            _cdQuote.Clear();
            _sdQuote.Clear();
            resultsTextBox.Clear();

            HttpClient _httpClient = new HttpClient();
            List<Task> _taskList = new List<Task>();
            foreach (string _symbol in ListDJIA)
            {
                _taskList.Add(GetQuoteAsync(_symbol, _httpClient, CT));
            }
            await Task.WhenAll(_taskList);

            // test if count is 30 (DJIA stocks)
            resultsTextBox.Text += String.Concat("Dictionary Items: ", _dQuote.Count, Environment.NewLine);
            resultsTextBox.Text += String.Concat("Dictionary Items: ", _cdQuote.Count, Environment.NewLine);
            resultsTextBox.Text += String.Concat("Dictionary Items: ", _sdQuote.Count, Environment.NewLine); 
        }

        /// <summary>
        /// Get quote from web in async mode
        /// </summary>
        /// <param name="Symbol">string</param>
        /// <param name="client">HttpClient</param>
        /// <param name="CT">CancellationToken</param>
        /// <returns>Task</returns>
        async Task GetQuoteAsync(string Symbol, HttpClient client, CancellationToken CT) {
            try {
                HttpResponseMessage _response = await client.GetAsync(_baseUrl + Symbol, CT);
                // bytes array
                byte[] _arrContentBytes = await _response.Content.ReadAsByteArrayAsync();
                // bytes array to string
                string quote = System.Text.Encoding.UTF8.GetString(_arrContentBytes);

                // try parse Stock Px as double
                double _dbl;
                if (double.TryParse(quote,out _dbl))
                {
                    // add item to dictionary (simplest option)
                    _dQuote.Add(Symbol, _dbl);
                    // add item to sorted dictionary (desirable option)
                    _sdQuote.Add(Symbol, _dbl);
                    // add item to concurrent dictionary (guaranteed thread-safe option)
                    _cdQuote.TryAdd(Symbol, _dbl);
                }
            }
            catch { throw; }
        }
    }
}

现在我收到了错误

def self.get(code)
 where(code: normalize_code(code)).
 where('coupon_count > 0').
 where('expires_at > Time.now OR expires_at IS NULL').
 take
end

错误发生在＆＃34; take＆＃34;线

-UPDATE -

我的错误在于coupon_count的where方法。它不在take方法中。我必须弄清楚在接受优惠券之前它不会检查coupon_count字段。

Answer 1

http://apidock.com/rails/ActiveRecord/FinderMethods/take文档似乎说take默认将返回限制为1.

Person.take # returns an object fetched by SELECT * FROM people LIMIT 1我

然而，错误消息告诉我take需要参数。查看下面这个问题（Arrays in Ruby: Take vs Limit vs First）中答案的注释，它基本上总结了在Ruby 1.8.7,1.9.3,2.0.0或2.1.0中不能在没有参数的情况下调用Take。

Answer 2

由于您只选择一个，所以为什么不尝试先使用。

通过查询Rails获取错误

2 个答案: