一、需求

系统中存在基本字典数据，且数据量大，需要根据各种条件查询某个字典数据，该如何高效实现？

例如：系统中的菜品字典数据，需要根据菜品ID、菜品编码、菜品名+菜品规格等条件查找菜品

二、思路

1、使用索引的方法

将每个查询条件都建立一个TStringList，并添加条件值，并确保其与菜品对象 TMenuItem 在TList中的位置一样。 查询时，根据条件值找到TStringList中的位置 index，然后直接通过TList[index] 获取菜品对象。

该方法查询时不用遍历整个 TList ，从而提高查询效率。

2、使用哈希方法

将每个查询条件添加到 TDictionary 字典 TFMenuItemHash(TDictionary<string, TMenuItem>)，Key 值为 【条件前缀+菜品对应ID等值】，Value 值为 TMenu 对象地址。查询时，通过FMenuItemHash.TryGetValue 获取。

注意：程序结束时，需要遍历 TFMenuItemHash，释放 TFMenuItemHash 对应的 TMenu 对象

三、代码实现

这里只展示思路2对应的代码实现。

unit uMenuItem;interfaceusesWinapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, System.Generics.Collections;//定义查询条件类型  按菜品ID  菜品Key  菜品编码  菜品名称  菜品名称+规格  菜品ID+规格
typeTMenuItemListType = (mltID, mltKey, mltCode, mltName, mltNameUnit, mltIDUnit, mltKeyUnit);
constMenuItemListTypeArry: array [TMenuItemListType] of string = ('mltID', 'mltKey', 'mltCode', 'mltName', 'mltNameUnit', 'mltIDUnit', 'mltKeyUnit');type//菜品类TMenuItem = class//...菜品ID、菜品名等属性end;//菜品字典列表类TMenuItemLst = classprivateFMenuItemHash: TDictionary<string, TMenuItem>;//添加Key值到 FMenuItemHash 中procedure AddMenuItem(MenuItemType: TMenuItemListType; AKey: string; AMenuItem: TMenuItem);//从 FMenuItemHash 中获取 key 值对应的 TMenuItem 对象function GetMenuItem(MenuItemType: TMenuItemListType; AKey: string): TMenuItem;function InitData(): boolean;function GetCount: integer;function GetItems(Index: integer): TMenuItem;protectedFList: TList<TMenuItem>;publicconstructor Create(); overload;destructor Destroy; override;property Count: integer read GetCount;property Items[Index: integer]: TMenuItem read GetItems; default;procedure Clear;procedure ClearFoodCannotSaleList;procedure Delete(iIndex: integer);function IndexOf(AMenuItem: TMenuItem): integer;function Refresh(): Boolean;//按菜品ID查询function GetMenuItemByFoodID(AFoodID: int64): TMenuItem;//按菜品规格查询function GetMenuItemByUnitKey(AUnitKey: string): TMenuItem;//按菜品编码查询function GetMenuItemByFoodCode(AFoodCode: string): TMenuItem;//按菜品名称查询function GetMenuItemByFoodName(AFoodName: string): TMenuItem;//按菜品名称+规格查询function GetMenuItemByFoodNameUnit(AFoodName, AFoodUnit: string): TMenuItem;//按菜品ID+规格查询function GetMenuItemByFoodIDUnit(AFoodID: int64; AFoodUnit: string): TMenuItem;//按菜品Key+规格查询function GetMenuItemByFoodKeyUnit(AFoodKey, AFoodUnit: string): TMenuItem;
end;implementation{ TMenuItemLst }procedure TMenuItemLst.Clear;
vari: integer;
beginfor i := 0 to FList.Count - 1 dobeginFList[i].Free;end;FList.Clear;FMenuItemHash.Clear;
end;constructor TMenuItemLst.Create;
beginFList := TList<TMenuItem>.Create;FMenuItemHash := TDictionary<string, TMenuItem>.Create;
end;procedure TMenuItemLst.Delete(iIndex: integer);
beginTMenuItem(FList[iIndex]).Free;FList.Delete(iIndex);
end;destructor TMenuItemLst.Destroy;
beginClear;FList.Free;FMenuItemHash.Free;inherited;
end;function TMenuItemLst.GetCount: integer;
beginResult := FList.Count;
end;procedure TMenuItemLst.AddMenuItem(MenuItemType: TMenuItemListType;AKey: string; AMenuItem: TMenuItem);
beginFMenuItemHash.AddOrSetValue(MenuItemListTypeArry[MenuItemType] + AKey, AMenuItem);
end;function TMenuItemLst.GetMenuItem(MenuItemType: TMenuItemListType;AKey: string): TMenuItem;
beginFMenuItemHash.TryGetValue(MenuItemListTypeArry[MenuItemType] + AKey, Result);
end;function TMenuItemLst.GetItems(Index: integer): TMenuItem;
beginResult := nil;if (Index >= 0) and (Index < FList.Count) thenResult := TMenuItem(FList[Index]);
end;function TMenuItemLst.GetMenuItemByFoodCode(AFoodCode: string): TMenuItem;
beginResult := GetMenuItem(mltCode, AFoodCode);
end;function TMenuItemLst.GetMenuItemByFoodID(AFoodID: int64): TMenuItem;
beginResult := GetMenuItem(mltID, AFoodID.ToString);
end;function TMenuItemLst.GetMenuItemByFoodIDUnit(AFoodID: int64;AFoodUnit: string): TMenuItem;
beginResult := GetMenuItem(mltIDUnit, AFoodID.ToString + AFoodUnit);
end;function TMenuItemLst.GetMenuItemByFoodKeyUnit(AFoodKey,AFoodUnit: string): TMenuItem;
beginResult := GetMenuItem(mltKeyUnit, AFoodKey + AFoodUnit);
end;function TMenuItemLst.GetMenuItemByFoodName(AFoodName: string): TMenuItem;
beginResult := GetMenuItem(mltName, AFoodName);
end;function TMenuItemLst.GetMenuItemByFoodNameUnit(AFoodName,AFoodUnit: string): TMenuItem;
beginResult := GetMenuItem(mltNameUnit, AFoodName + AFoodUnit);
end;function TMenuItemLst.GetMenuItemByUnitKey(AUnitKey: string): TMenuItem;
beginResult := GetMenuItem(mltKey, AUnitKey);
end;function TMenuItemLst.IndexOf(AMenuItem: TMenuItem): integer;
beginResult := FList.IndexOf(AmenuItem);
end;function TMenuItemLst.InitData(): boolean;
vari: integer;menuItem: TMenuItem;foodID, foodUnitKey, foodCode, foodName, foodUnit: string;
beginresult := false;trytry//循环数据集， 假如已从数据库中查询了所有菜品字典数据for i := 0 to 10000 dobegin//初始化菜品对象，在 TMenuItemLst 类释放时，需要循环释放 TMenuItemmenuItem := TMenuItem.Create();foodID := menuItem.FoodID;foodUnitKey := menuItem.FoodUnitKey;foodCode := menuItem.FoodCode;foodName := menuItem.FoodName;foodUnit := menuItem.FoodUnit;if foodID <> '' then           //添加菜品ID的Key值AddMenuItem(mltID, foodID, menuItem);if foodUnitKey <> '' then      //添加菜品Key的Key值AddMenuItem(mltKey, foodUnitKey, menuItem);if FoodCode <> '' then         //添加菜品编码的Key值AddMenuItem(mltCode, foodCode, menuItem);if foodName <> '' thenAddMenuItem(mltName, foodName, menuItem);if (foodName <> '') or (foodUnit <> '') thenAddMenuItem(mltNameUnit, foodName + foodUnit, menuItem);if (foodID <> '') or (foodUnit <> '') thenAddMenuItem(mltIDUnit, foodID + foodUnit, menuItem);if (foodUnitKey <> '') or (foodUnit <> '') thenAddMenuItem(mltKeyUnit, foodUnitKey + foodUnit, menuItem);FList.Add(menuItem);end;result := true;excepton E: Exception dobeginraise Exception.Create(E.Message);end;end;finallyend;
end;function TMenuItemLst.Refresh(): Boolean;
beginend;end.