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https://github.com/filipw/async-expiring-lazy
AsyncExpiringLazy
https://github.com/filipw/async-expiring-lazy
Last synced: 7 days ago
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AsyncExpiringLazy
- Host: GitHub
- URL: https://github.com/filipw/async-expiring-lazy
- Owner: filipw
- License: mit
- Created: 2016-11-01T13:46:25.000Z (about 8 years ago)
- Default Branch: master
- Last Pushed: 2024-10-19T15:02:09.000Z (26 days ago)
- Last Synced: 2024-10-31T14:36:15.258Z (14 days ago)
- Language: C#
- Size: 57.6 KB
- Stars: 37
- Watchers: 4
- Forks: 7
- Open Issues: 2
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# Async Expiring Lazy
See [blog article](https://www.strathweb.com/2016/11/lazy-async-initialization-for-expiring-objects/) for more background details and a [follow up post](https://www.strathweb.com/2021/07/eager-refresh-of-values-for-asyncexpiringlazy/) for further update.
## Installation
Grab the Nuget package called [Strathweb.AsyncExpiringLazy](https://www.nuget.org/packages/Strathweb.AsyncExpiringLazy/). It is cross compiled for .NET Standard 1.1, .NET Standard 2.0 and .NET Framework 4.6.1 and compatible with:
- .NET Framework 4.6.1
- all version of .NET Core
- Xamarin
- Mono
- Universal Windows Platform
Latest version: [](https://www.nuget.org/packages/Strathweb.AsyncExpiringLazy/)
## Usage
The code sample shows creating a lazy epxiring value with `AsyncExpiringLazy` and letting it get recreated on first reuse after expiration.
```csharp
var testInstance = new AsyncExpiringLazy(async (metadata, ct) =>
{
await Task.Delay(1000, ct);
return new ExpirationMetadata
{
Result = new TokenResponse
{
AccessToken = Guid.NewGuid().ToString()
}, ValidUntil = DateTimeOffset.UtcNow.AddSeconds(2)
};
});
// 1. check if value is created - shouldn't
Assert.False(await testInstance.IsValueCreated());
// 2. fetch lazy expiring value
var token = await testInstance.Value();
// 3a. verify it is created now
Assert.True(await testInstance.IsValueCreated());
// 3b. verify it is not null
Assert.NotNull(token.AccessToken);
// 4. fetch the value again. Since it's lifetime is 2 seconds, it should be still the same
var token2 = await testInstance.Value();
Assert.Same(token, token2);
// 5. sleep for 2 seconds to let the value expire
await Task.Delay(2000);
// 6a. verify the value expired
Assert.False(await testInstance.IsValueCreated());
// 6b. fetch again
var token3 = await testInstance.Value();
// 7. verify we now have a new (recreated) value - as the previous one expired
Assert.NotSame(token2, token3);
// 8. invalidate the value manually before it has a chance to expire
await testInstance.Invalidate();
// 9. check if value is created - shouldn't anymore
Assert.False(await testInstance.IsValueCreated());
```
The next code sample shows creating a lazy epxiring value with `AsyncExpiringEager` and letting it get recreated silently as soon as it expires.
Pay attetion to the different from the previous example at step `6a`.
```csharp
using var testInstance = new AsyncExpiringEager(async (metadata, ct) =>
{
await Task.Delay(1000, ct);
return new ExpirationMetadata
{
Result = new TokenResponse
{
AccessToken = Guid.NewGuid().ToString()
}, ValidUntil = DateTimeOffset.UtcNow.AddSeconds(2)
};
});
// 1. check if value is created - shouldn't
Assert.False(testInstance.IsValueCreated());
// 2. fetch lazy expiring value
var token = await testInstance.Value();
// 3a. verify it is created now
Assert.True(testInstance.IsValueCreated());
// 3b. verify it is not null
Assert.NotNull(token.AccessToken);
// 4. fetch the value again. Since it's lifetime is 2 seconds, it should be still the same
var token2 = await testInstance.Value();
Assert.Same(token, token2);
// 5. sleep for 2 seconds to let the value expire
await Task.Delay(2000);
// 6a. verify the value was eagerly created just before it expired
Assert.True(testInstance.IsValueCreated());
// 6b. fetch again
var token3 = await testInstance.Value();
// 7. verify we now have a new (recreated) value - as the previous one expired
Assert.NotSame(token2, token3);
// 8. invalidate the value manually before it has a chance to expire
testInstance.Invalidate();
// 9. check if value is created - shouldn't anymore
Assert.False(testInstance.IsValueCreated());
```
## License
[MIT](https://github.com/filipw/async-expiring-lazy/blob/master/LICENSE)