stream_trigger 1.0.0

The Stream Trigger object does exactly what the name implies. Stream Trigger can be used to either 'trigger' transformations to particular data on data streams, or trigger logic to happen elsewhere, o [...]

example/stream_trigger.dart

// Copyright (c) 2015, Will Squire. All rights reserved. Use of this source code
// is governed by a BSD-style license that can be found in the LICENSE file.

library stream_trigger.example;

import 'package:stream_trigger/stream_trigger.dart';
import 'dart:convert';
import 'dart:io';

main() {
  // This will be our trigger in the stream, the string
  // "<your name>" is encoded in UTF format (List<int> type)
  List<int> utfEncodedString = UTF8.encode("<your name>");

  // Stream Trigger requires a Map object to be supplied,
  // where the maps' keys are the 'triggers' and values are
  // the 'handlers'. (Note, handlers MUST be a function with
  // a return value)
  Map<List<int>,TriggerHandle> triggerHandles = new Map<List<int>,TriggerHandle>();

  triggerHandles[utfEncodedString] = () {
    // Stuff here will be executed when the trigger (which
    // in this case is '<your name>', in a UTF encoded
    // format) occurs in sequence on the stream.
    print("Trigger has invoked handler");

    // This function MUST return what element/s replace the
    // trigger on the stream, if no change is to occur to
    // the trigger element/s, return null. Else return what
    // will replace the trigger on the stream. (Note,
    // other stream objects can also be returned by the
    // handler to 'inject' one stream into another.
    return UTF8.encode("Will Squire");
  };

  // Stream Trigger requires the trigger/handler map on
  // instantiation.
  StreamTrigger streamTrigger = new StreamTrigger(triggerHandles);

  // Next a stream is needed to apply the Stream Trigger
  // to. The Stream Trigger is a type of Stream Transformer
  // and is fed into the .transform() function like so.
  // (Note, '../LICENSE' might not be a valid location on
  // your system, change as needed).
  new File(new Uri.file('../LICENSE').toFilePath())
    .openRead()
    .transform(streamTrigger)
    .transform(UTF8.decoder)
    .listen((String char) {
      // Stream with Stream Trigger alterations taking place,
      // which in the given example, will replace any
      // occurrences of '<your name>' with 'Will Squire'.
      // (Note that no alterations need to be made to the
      // stream, it could simply return null and carry out
      // other operations).
      print(char);
    });

  // A shorter way you might write a Stream Trigger is like 
  // so
  StreamTrigger triggerWithStreamInjection = new StreamTrigger({
    UTF8.encode("A library useful for applications or for sharing on pub.dartlang.org.") : () {
      // Note, a stream of the same type can also be returned 
      // here to merge one stream into another, like so.
      return new File(new Uri.file('../README.md')
        .toFilePath())
        .openRead();
    }
  });
  
  new File(new Uri.file('../pubspec.yaml').toFilePath())
    .openRead()
    .transform(triggerWithStreamInjection)
    .transform(UTF8.decoder)
    .listen((String char) {
      // And get the data here... etc
      print(char);
    });
}