Mega Code Archive
Sorting your items with control over the sort algorithm
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Title: Sorting your items with control over the sort algorithm
Question: We need to sort items in a list but we want to adress the objects in the list to do the sort .
Answer:
Did you ever wanted to sort some lists with your own sorting algoritme?
Here some ways of doing just that.
In this example we show you how to sort a TList and a TStringList
using the objects in it to do the sorting on.
Notice the diverence :)
We assume you initialized the lists and filled it with TMyObject's
type
TForm1 = Class(TForm)
AListBox : TListBox ;
Public
StringList: TStringList;
MyList : TList ;
end;
TMyObject = class
SomeInt : integer;
SomeString : string;
end;
//For a TList Declare the function like this
//TListSortCompare = function (Item1, Item2: Pointer): Integer;
function MySort(Item1, Item2: Pointer): Integer;
// And for ATStringList
// TStringListSortCompare = function(List: TStringList; Index1, Index2:
// Integer): Integer;
function MyStringListSort (List: TStringList; Index1, Index2: Integer):integer;
implementation
function MySort(Item1, Item2: Pointer): Integer;
begin
// Bigger is 1, smaller is -1 and equals is 0
if TMyObject(Item1).SomeInt result := 1
else if TMyObject(Item1).SomeInt TMyObject(Item2).SomeInt then
result := -1
else
result = 0;
end;
function MyStringListSort (List: TStringList; Index1, Index2: Integer):integer;
begin
// Bigger is 1, smaller is -1 and equals is 0
if TMyObject(List.Objects[Item1]).SomeInt [Item2]).SomeInt then
result := 1
else if TMyObject(List.Objects[Item1]).SomeInt TMyObject(List.Objects
[Item2]).SomeInt then
result := -1
else
result = 0;
end;
procedure SomeClick(Sender : TObject);
begin
// if its a TList you are sorting then do it like this
MyList.Sort(MySort) ;
// if its a stringlist you are sorting then do it like this
StringList.CustomSort(MyStringListSort);
//if you want to make it visible then just assign mylist to a Tlistbox.Items
AListBox.items.assign(StringList);
end;
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