Reputation: 41
Maybe this is not necessarily a reselect question
const makeSelectError = () => createSelector(
selectGlobal,
(globalState) => globalState.get('error')
);
and in reselect we use
const mapStateToProps = createStructuredSelector({
error: makeSelectError(),
});
why can't we use like below?
const makeSelectError = createSelector(
selectGlobal,
(globalState) => globalState.get('error')
);
and use like below in reselect
const mapStateToProps = createStructuredSelector({
error: makeSelectError,
});
Are there any issues/disadvantages with my code, or is that a standard practice?
Upvotes: 2
Views: 5187
Reputation: 1584
Not only is the second way valid and correct it has other advantages.
With the first snippet you provide:
const makeSelectError = () => createSelector(
selectGlobal,
(globalState) => globalState.get('error')
);
makeSelectError
is a factory function in that every time it is called it is returning a new and unique selector.
This means that every time a simple mapStateToProps
function is called a new selector will be made and the result of the selector will be computed again.
This means that you will be losing the key benefit of reselect
that is memoization.
So for simple cases you could just do the following:
const getSomePieceOfState = state => state.someArea.someDetail;
const getAnotherPieceOfState = state => state.anotherArea.anotherItem;
const getSomeCombinedState = createSelector(
getSomePieceOfState,
getAnotherPieceOfState,
(somePiece, anotherPiece) => somePiece + anotherPiece
);
const mapStateToProps = state => ({
someProp: getSomeCombinedState(state)
});
Note. it's common to prefix the name of selectors with get
and to prefix the name of a selector factory (a function that returns a selector) with makeGet
.
Some times creating a selector factory is necessary though if you wan't to make a selector that is dependant on a property that is not in the state.
You can read more about that here Accessing React Props in Selectors
Upvotes: 4
Reputation: 2261
You're doing it absolutely right in the second example. This is a standard practice.
There's no need to do wrap makeSelectError
to another function.
Upvotes: 1