CODEWITHSUNDEEP
delphidelphi-7
Hijerarhija Uzasa
Hijerarhija Uzasa

Reputation: 193

How to sort list by first number?

I have a huge list of users and every user has it's id , but it id numbers are messed up so if anyone can show me how can I sort users by numbers , every value has this form 

1:Stackoverflow
or
145000:Google

If I do that manually I think I will lose my mind since tehere are more than 700000 records.Thanks for your time and help....

Upvotes: 2

Views: 365

Answers (1)

David Heffernan
David Heffernan

Reputation: 613612

Extract the number like this:

function ID(const str: string): Integer;
var
  p: Integer;
begin
  p := Pos(':', str);
  if p=0 then
    raise Exception.CreateFmt('Invalid string format: %s', [str]);
  Result := StrToInt(Copy(str, 1, p-1));
end;

Once you can extract the ID as an integer you can then write a compare function. Like this:

function CompareIDs(List: TStringList; Index1, Index2: Integer): Integer;
begin
  Result := CompareValue(
    ID(List[Index1]), 
    ID(List[Index2])
  );
end;

CompareValue is an RTL function that returns -1, 0 or 1 depending on the relative values of the two operands.

Feed these building blocks into TStringList.CustomSort and your job is done.

MyStringList.CustomSort(CompareIDs);

Upvotes: 10

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