README

Delphi Dataset Iterator

A modern, highly decoupled Delphi library implementing the Iterator and Decorator patterns to provide clean, robust, and safe iterations over TDataSet.

This library eliminates boilerplate code (like First, Next, Eof checks, and DisableControls/EnableControls), reducing cognitive load and preventing common bugs like infinite loops and memory leaks.

🚀 Features

• For-In Loop Support: Native enumerator support for any TDataSet descendant.
• Fluent ForEach (Closures): Iterate using anonymous methods.
• Decorator Pattern: Highly extensible state management during iterations without polluting the core logic.
  • Bookmark Decorator: Automatically saves and restores the cursor position.
  • Controls Decorator: Temporarily disables UI controls to boost performance during bulk iterations.
  • First Decorator: Automatically calls .First before iterating.
  • Filter Decorator: Safely ignores active filters during iteration and restores them afterward.
• Clean Code & SOLID: Zero if statements inside the iteration engine, fully extensible via Interfaces.

📦 Installation

Simply add the src folder to your Delphi Library Path, or add DatasetIterator.pas directly to your project.

🛠️ Usage Examples

First, add the unit to your uses clause:

uses DatasetIterator;

1. Modern For-In Loop

By default, the for..in loop uses the Bookmark, Controls, and First decorators automatically.

for var DS in ClientDataset do
begin
  ShowMessage('Name: ' + DS.FieldByName('Name').AsString);
end;

2. Functional ForEach with Custom Decorators

You can explicitly define which decorators should run during the iteration.

ClientDataset.ForEach(
  procedure(DS: TDataSet)
  begin
    ShowMessage('ID: ' + DS.FieldByName('ID').AsString);
  end,
  [TDatasetIterationConfigBookmark, 
   TDatasetIterationConfigControls, 
   TDatasetIterationConfigFirst]
);

3. Ignoring Active Filters (Filter Decorator)

If your dataset is currently filtered but you need to iterate over all records without losing the user's filter state:

ClientDataset.ForEach(
  procedure(DS: TDataSet)
  begin
    // Iterates all records, ignoring the active filter
  end, 
  [TDatasetIterationConfigBookmark, 
   TDatasetIterationConfigFirst, 
   TDatasetIterationConfigFilter] // <-- Disables filter, iterates, and restores it
);

🏗️ Architecture

This project is structured using the Decorator Pattern. The core TDataSetHelper and TDatasetEnumerator handle only the iteration logic. The responsibility of managing the dataset's state (Bookmarks, Controls, Filters) is delegated to classes implementing IDatasetIterationConfigDecorator.

This means you can easily create your own custom decorators without modifying the library's source code!

🤝 Contributing

Contributions, issues, and feature requests are welcome!

📝 License

This project is licensed under the MIT License.