Conditionally composing a selector using reselect

Question

export const mySelector = createSelector(
    [selectorA, selectorB], // but I want selectorB or selectorC to be chosen here using logic
    (foo, bar) => {
        // ...
    }
);

I want to conditionally use selectorB or selectorC when creating this selector based on the state in the store (i.e. the value returned by another selector).

How can I do this?

Have not tried reselect. What issue are you having using logic to determine the value? — guest271314, Nov 03 '17 at 12:56

score 10 · Accepted Answer · answered Nov 04 '17 at 22:51

10

Just to point out that the approach suggested in the accepted answer would evaluate both selectorB and selectorC on each selectorCorB call. Which is not probably the desired behaviour.

An actual conditional call might be implemented like this:

export const selectorCorB = createSelector(
    selectorStateX
    (...arguments) => arguments,
    (x, arguments) => x ? selectorB(...arguments) : selectorC(...arguments)
);

answered Nov 04 '17 at 22:51

Andrea Carraro

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`(...arguments) => arguments,` this would call the selector on any state change – Kevin K. Sep 17 '21 at 11:44

Shishir Arora · Answer 2 · 2017-11-03T13:12:51.300

then make a selectorCorB composing selectorB, selectorC , selectorX

selectorX is the selector of that variable x from store which decides either selectorB or selectorC

const selectorCorB = createSelector(
  selectorB,
  selectorC,
  selectorStateX,
  (b, c, x) => x? b: c
) 

mySelector = createSelector(
    [selectorA, selectorCorB], // will be A AND B OR C depending on x
    (foo, cOrb) => {
        // ...
    }
);

Conditionally composing a selector using reselect

2 Answers2