# Filter console

A console program that goes deeper into `TAtlasDataFilter`, `TAtlasFilterEdit`, `TAtlasDBGrid.ExportCSV` and
`TAtlasDBLookupCombo`, using a six-row FireDAC `TFDMemTable` of customers and a three-row table of categories.
It checks, in order:

1. contains, prefix and exact matching, case-insensitive, with the record count after each `Apply`;
2. that the text match composes with the dataset's own `Filter` expression and with an existing
   `OnFilterRecord` handler, and that `Clear` restores both;
3. that a second filter cannot take over the dataset, that `Apply` refuses to run during an edit, and that an
   unknown field name keeps the previous filter;
4. that typing into a `TAtlasFilterEdit` applies the filter and clearing it removes the filter;
5. CSV export of the filtered, visible columns, of the selected rows only, to `customers.csv`, and the refusal
   to export while an edit is pending;
6. lookup selection by display text and by key, with the master record left in edit state and the lookup
   cursor left where it was.

The controls are created on a form that is never shown; the data-aware controls need a parent window, not a
visible one. Every step checks its own result. The program exits with code 0 when all checks pass, or prints
the failed check and exits with code 1. It needs no input, database server or network.

## Build and run

Open `FilterConsole.dpr` in Delphi 13; the IDE creates the project file. Add the Atlas Info `src` folder and the Atlas VCL `src` folder to the project's search path, then build and run for Win32 or Win64. No packages need to be installed. The program needs no input. It checks its own results and stops with an error if any of them differs from the output below.

It writes `customers.csv` to the current directory.

## Expected output

```
1. Text matching
  ok  contains "ar" matches 4 of 6 names, case-insensitive
  ok  Filter.Text holds the lower-cased text
  ok  the filter is installed on the dataset
  ok  prefix "a" matches Acorn Design and Anchor Marine
  ok  exact match finds one record
  ok  Clear shows every record again
2. Composing with an existing filter
  ok  the native expression alone keeps 4 records
  ok  text match AND native expression keeps 2 records
  ok  Clear restores the native expression
  ok  text match runs after the existing OnFilterRecord handler
  ok  Clear restores the existing handler
3. Ownership and editing rules
  ok  a second controller cannot take over the dataset
  ok  Apply refuses to run while a record is being edited
  ok  an unknown field keeps the previous filter
4. TAtlasFilterEdit drives the controller
  ok  typing "ce" leaves Cedar Systems
  ok  clearing the edit clears the filter
5. CSV export of the visible rows
  ok  header plus the two filtered records
  ok  hidden columns are left out of the header
  ok  numbers and booleans use invariant text
  ok  export restores the current record
  ok  SelectedOnly exports the selected rows
  wrote ...\customers.csv
  ok  export refuses pending edits instead of posting them
6. Lookup selection
  ok  SelectText finds "Priority" from a prefix
  ok  the master field changed, nothing was posted
  ok  the lookup cursor did not move
  ok  an unknown text returns False
  ok  an unknown key raises and leaves the record alone
  ok  SelectKey followed by Post stores the key
PASS: 28 checks
```

`customers.csv` holds the two customers whose names start with "a", without the hidden `CategoryID` column:

```
ID,Name,Balance,Active
1,Acorn Design,1200.5,true
6,Anchor Marine,300,true
```

## Adapting it

Point `Filter.DataSet` at your own dataset and change the field names passed to `Apply`. To filter as the user
types, keep the `TAtlasFilterEdit` part and drop the direct `Apply` calls. To export something other than the
filtered rows, change which grid columns are visible before calling `ExportCSV`.