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// Generic types for FreeSparta.com and FreePascal!
// by Maciej Izak (hnb), 2014
program TComparerProject;
{$MODE DELPHI}
{$APPTYPE CONSOLE}
uses
SysUtils, Generics.Collections, Generics.Defaults;
type
{ TCustomer }
TCustomer = record
private
FName: string;
FMoney: Currency;
public
constructor Create(const Name: string; Money: Currency);
property Name: string read FName write FName;
property Money: Currency read FMoney write FMoney;
function ToString: string;
end;
TCustomerComparer = class(TComparer<TCustomer>)
function Compare(constref Left, Right: TCustomer): Integer; override;
end;
{ TCustomer }
constructor TCustomer.Create(const Name: string; Money: Currency);
begin
FName := Name;
FMoney := Money;
end;
function TCustomer.ToString: string;
begin
Result := Format('Name: %s >>> Money: %m', [Name, Money]);
end;
// Ascending
function TCustomerComparer.Compare(constref Left, Right: TCustomer): Integer;
begin
Result := TCompare.&String(Left.Name, Right.Name);
if Result = 0 then
Result := TCompare.Currency(Left.Money, Right.Money);
end;
// Descending
function CustomerCompare(constref Left, Right: TCustomer): Integer;
begin
Result := TCompare.&String(Right.Name, Left.Name);
if Result = 0 then
Result := TCompare.Currency(Right.Money, Left.Money);
end;
var
CustomersArray: TArray<TCustomer>;
CustomersList: TList<TCustomer>;
Comparer: TCustomerComparer;
Customer: TCustomer;
begin
CustomersArray := TArray<TCustomer>.Create(
TCustomer.Create('Derp', 2000),
TCustomer.Create('Sheikh', 2000000000),
TCustomer.Create('Derp', 1000),
TCustomer.Create('Bill Gates', 1000000000));
Comparer := TCustomerComparer.Create;
Comparer._AddRef;
// create TList with custom comparer
CustomersList := TList<TCustomer>.Create(Comparer);
CustomersList.AddRange(CustomersArray);
WriteLn('CustomersList before sort:');
for Customer in CustomersList do
WriteLn(Customer.ToString);
WriteLn;
// default sort
CustomersList.Sort; // will use TCustomerComparer (passed in the constructor)
WriteLn('CustomersList after ascending sort (default with interface from constructor):');
for Customer in CustomersList do
WriteLn(Customer.ToString);
WriteLn;
// construct with simple function
CustomersList.Sort(TComparer<TCustomer>.Construct(CustomerCompare));
WriteLn('CustomersList after descending sort (by using construct with function)');
WriteLn('CustomersList.Sort(TComparer<TCustomer>.Construct(CustomerCompare)):');
for Customer in CustomersList do
WriteLn(Customer.ToString);
WriteLn;
// construct with method
CustomersList.Sort(TComparer<TCustomer>.Construct(Comparer.Compare));
WriteLn('CustomersList after ascending sort (by using construct with method)');
WriteLn('CustomersList.Sort(TComparer<TCustomer>.Construct(Comparer.Compare)):');
for Customer in CustomersList do
WriteLn(Customer.ToString);
WriteLn;
WriteLn('CustomersArray before sort:');
for Customer in CustomersArray do
WriteLn(Customer.ToString);
WriteLn;
// sort with interface
TArrayHelper<TCustomer>.Sort(CustomersArray, TCustomerComparer.Create);
WriteLn('CustomersArray after ascending sort (by using interfese - no construct)');
WriteLn('TArrayHelper<TCustomer>.Sort(CustomersArray, TCustomerComparer.Create):');
for Customer in CustomersArray do
WriteLn(Customer.ToString);
WriteLn;
CustomersList.Free;
Comparer._Release;
ReadLn;
end.
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