Repeat

What it is

repeat executes the wrapped function multiple times, optionally until a condition is met. It can be used as a decorator or as a standalone helper.

When to use it

  • Polling loops.
  • Retrying with a custom condition.
  • Executing a side effect a fixed number of times.

Async / sync support

WrapperSupport
Func<R>✅ Async
Func1<T, R>✅ Async
Func2<T1, T2, R>✅ Async
FuncSync<R>❌ No

API reference 

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// api-reference
// As a decorator on Func<R>
Func<R> repeat({
  int? times,
  Duration? interval,
  bool Function(R result)? until,
  void Function(int iteration, R result)? onIteration,
});

// As a decorator on Func1<T, R>
Func1<T, R> repeat({
  int? times,
  Duration? interval,
  bool Function(R result)? until,
  void Function(int iteration, R result)? onIteration,
});

// As a decorator on Func2<T1, T2, R>
Func2<T1, T2, R> repeat({
  int? times,
  Duration? interval,
  bool Function(R result)? until,
  void Function(int iteration, R result)? onIteration,
});

Parameters

ParameterTypeDefaultDescription
timesint?nullMaximum number of repetitions. null means infinite, so always provide times or until.
intervalDuration?nullOptional delay between repetitions.
untilbool Function(R)?nullIf provided, stops early when the predicate returns true.
onIterationvoid Function(int, R)?nullCallback invoked after each iteration.

Examples

Basic example 

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var calls = 0;
final counter = Func<int>(() async => ++calls).repeat(times: 3);

print(await counter()); // 3

Real-world example 

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final waitForReady = Func<Status>(() async => await api.status() as Status).repeat(
  times: 20,
  until: (status) => status.ready,
  interval: Duration(seconds: 1),
);

print(await waitForReady());

Best practices

  • Always set a finite times to avoid infinite loops.
  • Use delay to avoid tight polling loops.
  • Combine with timeout() to add a hard deadline.

Common pitfalls

  • No delay polling: Without a delay, the loop can consume excessive CPU.
  • Until predicate never true: If until never matches, repeat returns the last result after times attempts.