SolidJS•16mo ago

Is it possible to subscribe to particular properties in a object wrapped by a store?

I have a usecase in which I have an object with say 100+ properties. I have some function which I would like to execute only when property 52 changes. Is it possible to do something like this?

    const someFunction = () => {
        if (props.data["property52"]) {
            // do something...
        } else {
            // do nothing
        }
    }

    const someFunction = () => {
        if (props.data["property52"]) {
            // do something...
        } else {
            // do nothing
        }
    }

Will this function only trigger whenever the value of property52 updates? Or when any value of the data object changes?

6 Replies

apollo79•16mo ago

If you have the data object as a store, it will only update when property52 updates, if it is a plain object, it will update if you replace the complete data object Here you will only see two logs of "rerunning": https://playground.solidjs.com/anonymous/d232c219-e131-4917-9bb0-c44e3c934b68

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TicTacManOP•16mo ago

Hi, thanks for the explanation! Do you know if there is a way to access the old value of store?

apollo79•16mo ago

Where do you want to access it?

TicTacManOP•16mo ago

Inside the getCalculatedValue function in: https://playground.solidjs.com/anonymous/8597e5cc-d702-4f6d-b8c6-ff4320bd1694

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TicTacManOP•16mo ago

Just a short description of what im trying to do: The third input field is a calculated field whose dependencies are supplied via an array called dependencies. Now I want to trigger an API call whenever any of the dependencies of the third field change In this case, input field 3 depends on data properties 50-55. Input field 1 changes property value 51 (so a change in field 1 should trigger an API call) and input field 2 changes property value 66 (a change in field 2 should not trigger an API call) The issue with my current example is that I need to maintain a separate array called "changedFields". Because on initial render, I would like field 3 to be empty since none of its dependencies have changed. the If I had access to the old value of the store, I would not need changedFields

apollo79•16mo ago

Okay... So what you could do would be just adding a isFirstRun variable or storing the current contents of the store after every rerun of getCalculatedValue, which would be much heavier I think. From what I can see, probably the isFirstRun is the cheaper version here. But the example is maybe a bit oversimplified, because I don't really know why you have that many fields, so there might be a better solution, but I can't see it from the context atm

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Is it possible to subscribe to particular properties in a object wrapped by a store?