Question

我有一个看起来像这样的循环

struct Flight_Details {
    char destination[99];
    char departure[99];
    char time_depart[80];
    char time_arrive[80];
    int flight_number;
};

switch (menu)
        {
            case MENU::NEW_FLIGHT: {
                Flight_Details flight_d;
                cout << "Enter Departure: ";
                cin >> flight_d.destination;
                cout << "Enter Destination: ";
                cin >> flight_d.departure;
                cout << "Enter Departure Time: ";
                cin >> flight_d.time_depart;
                cout << "Please enter arriving time: ";
                cin >> flight_d.time_arrive;
                cout << "Flight Number: ";
                cin >> flight_d.flight_number;

                ofstream file;
                file.open("Flgiht_Details.data", ios::binary);

                if (!file) cout << "Could create/open file";
                else {
                    file.write((char*)&flight_d, sizeof(flight_d));
                    file.close();
                }
                break;
            }
            case MENU::OUTPUT_FILE: {

                ifstream readFile;
                readFile.open("Flgiht_Details.data");
                if (!readFile) cout << "Couldn't open file";
                else {
                    readFile.seekg(0, ios::end);
                    int fileSize = readFile.tellg();
                    int countOfFlights = fileSize / sizeof(Flight_Details);
                    readFile.seekg(0, ios::beg);

                    Flight_Details* flight = new Flight_Details[countOfFlights];
                    readFile.read((char*)flight, countOfFlights *sizeof(Flight_Details));
                    readFile.close();

                    for (int i = 0; i < countOfFlights; i++)
                    {
                        cout << flight[i].destination << "\n" << flight[i].departure << "\n" << flight[i].time_depart << "\n" << flight[i].time_arrive << "\n" << flight[i].flight_number << "\n\n";
                    }
                    break;
                }
            }

            case MENU::EDIT: {
                Flight_Details* flight_d;
                ifstream readFile;
                readFile.open("Flgiht_Details.data");
                if (!readFile) cout << "Couldn't open file";
                else {
                    readFile.seekg(0, ios::end);
                    int fileSize = readFile.tellg();
                    int countOfFlights = fileSize / sizeof(Flight_Details);
                    readFile.seekg(0, ios::beg);

                    Flight_Details* flight = new Flight_Details[countOfFlights];
                    readFile.read((char*)flight, countOfFlights * sizeof(Flight_Details));
                    readFile.close();

                    ofstream file;
                    char edit[50];
                    cout << "Edit: ";
                    cin.getline(edit, 50);

                    for (int i = 0; i < countOfFlights; i++)
                    {
                        if (strcmp(flight_d[i].destination, edit) == 0)
                        {
                            //edit file
                        }
                    }

                }
            }       
        }

完美地显示属于用户的集合，然后显示每个集合中有多少个故事。

但是，我想使用这样做的助手。

视图中的

URIError: URI malformed
at decodeURIComponent( < anonymous > )
at Url.parse(url.js: 269: 19)
at Object.urlParse[as parse](url.js: 75: 5)
at Object.validateUrl[as validate](C: \node\ node_modules\ npm\ node_modules\ n opt\ lib\ nopt.js: 172: 13)
at validate(C: \node\ node_modules\ npm\ node_modules\ nopt\ lib\ nopt.js: 221: 24)
at validate(C: \node\ node_modules\ npm\ node_modules\ nopt\ lib\ nopt.js: 187: 11)
at C: \node\ node_modules\ npm\ node_modules\ nopt\ lib\ nopt.js: 104: 12
at Array.map(native)
at C: \node\ node_modules\ npm\ node_modules\ nopt\ lib\ nopt.js: 70: 15
at Array.forEach(native)

C: \node\ node_modules\ npm\ lib\ npm.js: 45
throw new Error('npm.load() required') ^

在帮手

中

<% @user.collections.each do |collection| %>
       <h1 class="impact"> <%= collection.name %><br></h1>
        <%=  collection.stories.count %>
<% end %>

我收到错误消息

<% @user.collections.each do |collection| %>
       <h1 class="impact"> <%= collection.name %><br></h1>
        <%=  number_of_stories_in_collection %>
<% end %>

感谢任何帮助，谢谢！

Answer 1

'collection'变量不是实例变量，因此帮助程序无法看到它。

将您的观点更改为：

<% @user.collections.each do |collection| %>
   <h1 class="impact"> <%= collection.name %><br></h1>
    <%=  number_of_stories_in(collection) %>
<% end %>

你的助手方法：

def number_of_stories_in(collection)
    collection.stories.count
end

这样您就可以正确地将变量传递给帮助程序。

Answer 2

扩展@ Richard的答案和一点点优化以避免n + 1个查询..

<% @user.collections.includes(:stories).each do |collection| %>
  <h1 class="impact"> <%= collection.name %><br></h1>
  <%=  render_stories_count(collection) %>
<% end %>

助手：

module CollectionsHelper
  def number_of_stories_in(collection)
    collection.stories.length
  end

  def render_stories_count(collection)
    if (count = number_of_stories_in(collection)).zero?
      'No stories in this collection yet'
    else
      "#{count} #{'story'.pluralize(count)}"
    end
  end
end

每个do循环中的Helper方法不起作用

2 个答案: