which type of comparer does mobx use ?

[prashantkn94]

I see there are different type of comparers in packages/mobx/src/utils/comparer.ts . But which type of comparison is actually done on the observables value before deciding whether to re-trigger render for React component.
Also, what comparer is used for reactivity in general ?

[mweststrate]

reference equality, which is in 98% of the cases the right choice. Not 100% sure whether that is `===` or `Object.is` from top of my head

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On Thu, Aug 31, 2023 at 8:03 PM prashantkn94 ***@***.***> wrote: I see there are different type of comparers in packages/mobx/src/utils/comparer.ts . But which type of comparison is actually done on the observables value before deciding whether to re-trigger component for React. Also, what comparer is used for reactivity in general ? — Reply to this email directly, view it on GitHub <#3751>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAN4NBBM3SSFDXA6U5MGKBDXYDGYLANCNFSM6AAAAAA4GOH6YY> . You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>

[prashantkn94]

reference equality would fail in case the observable is an object if any value of the key of the object is changed

[mweststrate]

no it normally won't, make sure to read up on the docs first to see how reactivity works in MobX.

[prashantkn94]

I have read the docs on reactivity. Let's say we have an observable object like below

@observable obj = { name: 'first', lastName": 'last' };

and we update it like below:

obj.name = "myName"

Now the reference of the obj is still the same but mobx will re-trigger the render. Please explain

[mweststrate]

MobX traps read and writes to all properties of observable objects, so if you read obj.name in observer, it will be detected and matched against future mutations of that property. See https://mobx.js.org/understanding-reactivity.html#understanding-reactivity or the original blog post: https://www.mendix.com/blog/making-react-reactive-pursuit-high-performing-easily-maintainable-react-apps/

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On Fri, Sep 1, 2023 at 4:31 PM prashantkn94 ***@***.***> wrote: I have read the docs on reactivity. Let's say we have an observable object like below @observable obj = { name: 'first', lastName": 'last' }; and we update it like below: obj.name = "myName" Now the reference of the obj is still the same but mobx will re-trigger the render. Please explain — Reply to this email directly, view it on GitHub <#3751 (reply in thread)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAN4NBEBGHISABRERKNZ4TTXYHWSLANCNFSM6AAAAAA4GOH6YY> . You are receiving this because you commented.Message ID: ***@***.***>