Question

我使用领域数据库，并从数据库在后台队列中加载数据。来自数据库的数据必须在后台加载，之后必须重新加载视图（TableView）。我如何在主线程的tableView上重新加载数据？

这种加载数据的方法：

func loadMenu(category: String) -> [Recipe] {

        var ingredient = [Ingredient]()
        var stage = [CookStage]()
        var photo = [PhotoDish]()
        var recipe = [Recipe]()
        DispatchQueue(label: "background").async {
            autoreleasepool {
                let realm = try! Realm()

                let data = realm.objects(Dish.self).filter("type = '\(category)'")
                print(data)
                for (index, value) in data.enumerated() {

                    for valIngredient in value.ingredient {
                        let ing = ["recipeID": valIngredient.recipeID,
                                   "name": valIngredient.name,
                                   "count": valIngredient.count,
                                   "weight": valIngredient.weight,
                                   "photo": valIngredient.photoURL,
                                   "image": self.loadImage(url: valIngredient.photoURL, dir: "ingredients") ] as [String: AnyObject]
                        let newIngredient = Ingredient(dict: ing as Dictionary<String,AnyObject>)
                        ingredient.append(newIngredient)
                    }
                    for valCook in value.cook {
                        let cook = ["stage": valCook.stage,
                                    "recipeID": valCook.recipeID,
                                    "photoUrl": valCook.photoUrl,
                                    "photo": self.loadImage(url: valCook.photoUrl, dir: "stage")] as [String:AnyObject]
                        let newStage = CookStage(dict: cook as Dictionary<String, AnyObject>)
                        stage.append(newStage)
                    }
                    for valFoto in value.foto {
                        let foto = ["url": valFoto.url,
                                    "recipeID": valFoto.recipeID,
                                    "image": self.loadImage(url: valFoto.url, dir: "compleate")] as [String:AnyObject]
                        let newPhoto = PhotoDish(dict: foto as Dictionary<String, AnyObject>)
                        photo.append(newPhoto)
                    }
                    let newElement = Recipe(name: value.name, count: value.eat, complexity: value.complexity, time: value.time, category: value.category, type: value.type, about: value.about, ingredient: ingredient, cook: stage, photo: photo, idOwner: value.idOwner, shared: value.shared, planing: value.planing, recipeID: value.recipeID)
                    recipe.append(newElement)
                }
            }
        }
        return recipe
    }

Answer 1

将数据加载到后台线程后，请使用：

DispatchQueue.main.async {
    myTable.reloadData()
}

Answer 2

//请使用完成处理程序。

#include <utility>

template <char ... Chars>
struct type_string_t {
    static constexpr const char data[sizeof... (Chars)] = {Chars...};
};

template <char s(std::size_t), std::size_t... I>
auto type_string_impl(std::index_sequence<I...>) {return type_string_t<s(I)...>();};

#define type_string(s) decltype (type_string_impl<[](std::size_t i) {return s[i];}> \
(std::make_index_sequence<sizeof (s)>()))

static_assert (std::is_same<type_string("String_A"),
                            type_string("String_A")>::value);
static_assert (!std::is_same<type_string("String_A"),
                             type_string("String_B")>::value);

在后台加载数据并重新加载tableView

2 个答案: