Сортировка TStringList по первой букве фамилии в Delphi

Delphi , Базы данных , Сортировка и Фильтр

Sorting TStringList by the first character after whitespace in Delphi

When working with strings in Delphi, you might encounter a scenario where you need to sort a TStringList not by the entire string, but by a specific part of it, such as the first character after whitespace. This can be useful when you have a list of full names and you want to sort them by last name. In this article, we'll explore how to achieve this using a custom sort function.

The Problem

You have a TStringList in Delphi containing full names (first name followed by last name, e.g., "John Smith"). You want to sort this list by last name, specifically by the first character after the space. Additionally, the strings may contain Unicode characters, such as Persian characters.

The Solution

To sort a TStringList by a specific part of the string, you can use the CustomSort method of TStringList. This method allows you to supply a custom compare function that compares two strings based on your specific requirements.

First, let's create a function that splits a full name into last name and the rest:

procedure SplitName(const Name: string; out Last, Rest: string);
var
  P: Integer;
begin
  P := Pos(' ', Name);
  if P = 0 then begin
    Last := Trim(Name);
    Rest := '';
  end else begin
    Last := Trim(Copy(Name, P+1, MaxInt));
    Rest := Trim(Copy(Name, 1, P-1));
  end;
end;

Next, we'll implement the custom compare function:

function NameCompareFunc(List: TStringList; Index1, Index2: Integer): Integer;
var
  Last1, Last2, Rest1, Rest2: string;
begin
  SplitName(List[Index1], Last1, Rest1);
  SplitName(List[Index2], Last2, Rest2);
  Result := AnsiCompareText(Last1, Last2);
  if Result = 0 then begin
    Result := AnsiCompareText(Rest1, Rest2);
  end;
end;

In this function, we first split the strings at index1 and index2 into last name and the rest. We then compare the last names using AnsiCompareText, which performs locale-aware comparison. If the last names are the same, we perform a secondary comparison on the rest of the name.

Finally, we can sort the TStringList using the custom compare function:

NameBuffer.CustomSort(NameCompareFunc);

Example

Here's an example demonstrating the usage of the custom compare function:

procedure TForm1.ButtonSortClick(Sender: TObject);
begin
  NameBuffer := TStringList.Create;
  NameBuffer.Separator := ';';
  NameBuffer.StrictOn := True;

  NameBuffer.Add('John Smith');
  NameBuffer.Add('Jane Doe');
  NameBuffer.Add('Ali Karimi');
  NameBuffer.Add('Sarah Johnson');

  NameBuffer.CustomSort(NameCompareFunc);

  Memo1.Lines.Assign(NameBuffer);
end;

In this example, clicking the "Sort" button will add some full names to the NameBuffer TStringList, sort it using the custom compare function, and display the sorted list in a TMemo component.

Conclusion

Sorting a TStringList by a specific part of the string, such as the first character after whitespace, can be achieved using the CustomSort method and a custom compare function. This approach allows you to sort strings based on your specific requirements, making it a powerful tool for handling complex sorting scenarios in Delphi.

Создано по материалам из источника по ссылке.

Эта статья объясняет, как отсортировать TStringList в Дельфи по первому символу после пробела в строке, полезно для сортировки списка полных имен по фамилии.

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