TAtlasCallbackSink

Create constructorinherited from TAtlasLogSink

constructor Create(AOwner: TComponent); override;

Creates the sink, not yet attached to a logger: set Logger to start receiving events. With an owner (a form, a data module or the logger itself) the sink is freed with it.

Destroy destructorinherited from TAtlasLogSink

destructor Destroy; override;

Leaves the logger first, so no event arrives during destruction, then frees the sink.

Logger propertyinherited from TAtlasLogSink

property Logger: TAtlasLogger read FLogger write SetLogger;

The logger this sink receives events from. Setting it registers the sink with that logger (and removes it from the previous one); nil detaches it. The same as calling TAtlasLogger.AddSink and RemoveSink. Either side may be destroyed first: the other is told and lets go.

Sink.Logger := Log;

MinLevel propertyinherited from TAtlasLogSink

property MinLevel: TAtlasLogLevel read FMinLevel write FMinLevel default llTrace;

The sink's own threshold: events below it are ignored by this sink only. It applies after the logger's threshold, so it can only narrow what the logger lets through. Default llTrace.

Files.MinLevel := llInfo;   // the file skips debug and trace

OnEvent event

property OnEvent: TAtlasLogEventHandler read FOnEvent write FOnEvent;

Called once per event that passes MinLevel. Without a handler, events are ignored.

Write methodinherited from TAtlasLogSink

procedure Write(const Event: TAtlasLogEvent);

Writes one event. The logger calls it; you may call it too, for example to replay events from a TAtlasMemorySink into another sink. Events below MinLevel and events at llOff are ignored; otherwise DoWrite runs under the sink's lock. Unlike the logger, Write itself may raise when the output fails.

Flush methodinherited from TAtlasLogSink

procedure Flush;

Pushes buffered output out, under the sink's lock. TAtlasLogger.Flush calls it on every sink and counts failures; called directly it may raise. A callback sink has nothing to flush.

Show the last error in the user interface

Errors from any thread reach the main thread through TThread.Queue.

uses System.Classes, System.SysUtils, Atlas.Log, Atlas.LogSinks;

type
  TErrorForwarder = class
  public
    LastError: string;
    procedure EventLogged(Sender: TObject; const Event: TAtlasLogEvent);
  end;

procedure TErrorForwarder.EventLogged(Sender: TObject; const Event: TAtlasLogEvent);
var
  Text: string;
begin
  Text := AtlasLevelCodes[Event.Level] + ' ' + Event.Message;
  // On the logging thread: hand the text to the main thread.
  TThread.Queue(nil, procedure begin LastError := Text; end);
end;

procedure WatchErrors(Log: TAtlasLogger; Forwarder: TErrorForwarder);
var
  Sink: TAtlasCallbackSink;
begin
  Sink := TAtlasCallbackSink.Create(Log);
  Sink.MinLevel := llError;
  Sink.OnEvent := Forwarder.EventLogged;
  Sink.Logger := Log;
end;