搜索通用列表 [英] search a Generic list

问题描述

我在修改一般搜索
因为我的类更复杂，我需要创建几个不同的搜索功能

I 'm trouble understanding in modifying the solution from GENERIC SEARCH as my class is more complex and I need to create several different search functions

procedure TForm1.Button1Click(Sender: TObject);
var
  activities: TList<TActivityCategory>;
  search: TActivityCategory;
begin
  activities := TObjectList<TActivityCategory>.Create(
    TDelegatedComparer<TActivityCategory>.Create(
     function(const Left, Right: TActivityCategory): Integer
       begin
       Result := CompareText(Left.Name, Right.Name);
       end)); 

  .....

假设我的TActivityCategory看起来像

Assume my TActivityCategory looks like

  TActivityCategory = class
    FirstName  : String;
    Secondname  : String;
    onemore .....
  end;

如何对我的活动类中的每个String进行搜索？

How to implement a search for every String inside my activtity class ?

推荐答案

在你的位置，我将写一个TObjectList的子类，并添加一个如下所示的自定义搜索方法：

In your place I would write a subclass of TObjectList and add a custom Search method that would look like this:

TSearchableObjectList<T:class> = class(TObjectList<T>)
public
  function Search(aFound: TPredicate<T>): T;
end;

该方法的实现是

function TSearchableObjectList<T>.Search(aFound: TPredicate<T>): T;
var
  item: T;
begin
  for item in Self do
    if aFound(item) then
      Exit(item);
  Result := nil;
end;

此方法的示例是

var
  myList: TSearchableObjectList<TActivitycategory>;
  item: TActivitycategory;
  searchKey: string;
begin
  myList := TSearchableObjectList<TActivitycategory>.Create;
  // Here you load your list
  searchKey := 'WantedName';
  // Let´s make it more interesting and perform a case insensitive search,
  // by comparing with SameText() instead the equality operator
  item := myList.Search(function(aItem : TActivitycategory): boolean begin
            Result := SameText(aItem.FirstName, searchKey);
          end);
  // the rest of your code
end;

上面使用的 TPredicate< T> SysUtils 中声明，所以请务必将其添加到您的uses子句中。

The TPredicate<T> type used above is declared in SysUtils, so be sure to add it to your uses clause.

我相信这是最接近的我们可以在Delphi中找到lambda表达式。

I believe this is the closest we can get to lambda expressions in Delphi.

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