CronJob

Using the WaCron Class for Scheduling Tasks

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The WaCron class is a powerful tool for scheduling and managing tasks at specified intervals. Below are practical examples demonstrating how to use this class effectively in different scenarios.

Example 1: Basic Task Execution Every 5 Seconds

To execute a task every 5 seconds, use the following configuration:

final cronJob = WaCron(
  schedule: '*/5 * * * * *', // Run every 5 seconds
  onCron: (count, cron) async {
    print('Task executed $count times');
  },
);

cronJob.start();

Explanation:

• Schedule: '*/5 * * * * *' indicates the job should run every 5 seconds.
• Callback Function: Prints the execution count each time the task runs.

Example 2: Delayed Start

If you want to start the task but delay the first execution, set delayFirstMoment to true:

final cronJob = WaCron(
  schedule: '*/10 * * * * *', // Run every 10 seconds
  onCron: (count, cron) async {
    print('Task executed $count times');
  },
  delayFirstMoment: true, // Delay the first execution
);

cronJob.start();

Explanation:

• delayFirstMoment: true: The first execution will only occur after the first scheduled interval, i.e., 10 seconds after starting.

Example 3: Immediate Execution on Start

To execute the task immediately upon starting, set delayFirstMoment to false:

final cronJob = WaCron(
  schedule: '*/15 * * * * *', // Run every 15 seconds
  onCron: (count, cron) async {
    print('Task executed $count times');
  },
  delayFirstMoment: false, // Immediate execution
);

cronJob.start();

Explanation:

• delayFirstMoment: false: Executes the task immediately upon starting, then continues according to the cron schedule.

Example 4: Convert Duration to Cron Expression

If you prefer to use a duration instead of a cron string, convert a Duration to a cron expression:

String cronExpr = WaCron.durationToCron(Duration(seconds: 30));
print(cronExpr); // Outputs: "*/30 * * * * *"

final cronJob = WaCron(
  schedule: cronExpr, // Use the converted cron expression
  onCron: (count, cron) async {
    print('Task executed $count times');
  },
);

cronJob.start();

Explanation:

• WaCron.durationToCron(Duration(seconds: 30)): Converts the duration into a cron expression that runs every 30 seconds.

Example 5: Stopping a Cron Job

To stop a running cron job and release resources:

final cronJob = WaCron(
  schedule: '*/60 * * * * *', // Run every 60 seconds
  onCron: (count, cron) async {
    print('Task executed $count times');
  },
);

cronJob.start();

// After some time, stop the cron job
Future.delayed(Duration(minutes: 5), () {
  cronJob.close();
  print('Cron job stopped.');
});

Explanation:

• cronJob.close(): Stops the cron job and releases resources. In this example, the cron job will be stopped after running for 5 minutes.

Summary

The WaCron class allows you to:

• Schedule tasks to run at specified intervals using cron expressions.
• Delay the first execution or run immediately.
• Convert Duration to cron expressions.
• Stop the cron job and clean up resources.

By configuring WaCron with the appropriate schedule and options, you can handle various task scheduling needs in your application efficiently.