Comments (2)
Hi!
You can pass the { lazy: true }
flag to do not run it immediately. If you pass it you have to call the returned reaction once later to kick-off the observation process. See the related docs section.
import { observable, observe } from '@nx-js/observer-util';
const counter = observable({ num: 0 });
+ // does not call countLogger
const countLogger = observe(() => console.log(counter.num), { lazy: true });
// this does not react yet, the returned reaction has to run once to kick off the observation process
counter.num++;
// this runs the reaction and starts the observation
countLogger()
// this also runs the reaction (observation is already started)
counter.num++;
This is useful when you don't own the control flow of the program. See my other lib (react-easy-state) for a real life example of the usage.
EDIT: you are right about side effect. The purpose of reactions are automated side-effects. Data derivation should always be done with JS getters instead.
from observer-util.
Ok, than the docs make sense as they are – thanks for clarification.
from observer-util.
Related Issues (20)
- Mutating observables in reactions is forbidden HOT 2
- 4.2.0 broke something HOT 3
- Trap "toJSON" to allow serialization of proxies HOT 2
- Deeply observe object HOT 12
- Is it possible to receive the type of change when observing a value? HOT 9
- Observables arrays don't appear to observe correctly HOT 3
- Question about scheduler batching and observe optimizations. HOT 2
- Problem when changing whole objects HOT 1
- Understanding reactions HOT 1
- Angular 7 Integration HOT 1
- Not sure I'm understanding this at all HOT 4
- Object.defineProperty should trigger reactions HOT 3
- computed properties no cache? HOT 3
- Observing through a Proxy HOT 2
- `construct` trap fails for observed constructors HOT 1
- Bug or user error? Copying observable to other position in array converts it to the raw item
- should observe explicit array length changes
- Shallow observing HOT 1
- rawToProxy WeakMap.set is never called
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from observer-util.