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About Cache
Cache provides:
- caching of values in memory;
- automatic deletion of values after expiration.
Set
To cache values, use the set method.
Example of using the set method to set values:
void main() {
var cache = Cache();
cache.set('name', 'Alex');
}
Get
To get the values, use the get method or the [] operator.
Example of getting values by key:
void main() {
var cache = Cache();
cache.set('name', 'Alex');
print(cache.get('name'));
print(cache['cache']);
}
Expected output:
Alex
Alex
Update
You can update an existing value and update its lifetime using the update method.
Example of updating a value:
void main(List<String> args) {
var cache = Cache(checkPeriod: const Duration(milliseconds: 250));
cache.set('name', 'Alex',
expirationSetting:
ExpirationSetting(expiration: const Duration(seconds: 1)));
Future.delayed(const Duration(milliseconds: 500), () {
cache.update('name', 'Tom');
});
Future.delayed(const Duration(milliseconds: 1300), () {
print(cache['name']);
});
Future.delayed(const Duration(milliseconds: 1600), () {
print(cache['name']);
cache.dispose();
});
}
Expected output:
Tom
null
Delete
You can delete a value using the delete method.
Example of deleting a value:
void main() {
var cache = Cache();
cache.set('name', 'Alex');
print(cache['name']);
cache.delete('name');
print(cache['name']);
}
Expected output:
Alex
null
Has
You can check the presence of a key value using the has method.
Example of checking for the presence of a value:
void main() {
var cache = Cache();
cache.set('name', 'Alex');
print(cache.has('name'));
print(cache.has('key'));
}
Expected output:
true
false
Expiration
In Cache there is an automatic clearing of values after a specified time.
You can set the lifetime of the value in the cache using the expirationSetting parameter of the set method.
Example of setting the lifetime of a value:
void main() {
var cache = Cache();
cache.set('name', 'Alex',
expirationSetting:
ExpirationSetting(expiration: const Duration(minutes: 15)));
}
To clear the Cache, there is an interval for checking the values to see if their lifetime has expired. By default, it is 600 seconds.
You can independently set the time of the interval for checking values using the checkPeriod parameter when creating an instance of the Cache class.
Example of setting the interval for checking values:
void main() {
var cache = Cache(checkPeriod: const Duration(seconds: 5));
}
If you do not plan to automatically clear the values after a while, you can disable this by using the deleteOnExpire parameter. By default, it is true.
Change expiration
After writing the value, you can change its lifetime using the changeExpiration method.
Example of changing the lifetime of a value:
void main() {
var cache = Cache();
cache.set('name', 'Alex',
expirationSetting:
ExpirationSetting(expiration: const Duration(minutes: 5)));
cache.changeExpiration(
'name', ExpirationSetting(expiration: const Duration(minutes: 1)));
}
Delete callback
When setting the lifetime of a value, you can also assign a handler that will trigger when the value is deleted after its expiration.
If the handler returns true, the value will be deleted. If the handler returns false, the lifetime of the value will be extended by the time set for it.
Example of installing a handler:
void main() {
var cache = Cache();
cache.set('name', 'Alex',
expirationSetting: ExpirationSetting(
expiration: const Duration(minutes: 5),
onDelete: (value) {
print(value);
return true;
}));
}
Clear
You can clear all the values in the cache using the clear method.
Example of clearing the cache value:
void main() {
var cache = Cache();
cache.set('name', 'Alex');
print(cache['name']);
cache.clear();
print(cache['name']);
}
Expected output:
Alex
null