function FlashcardScreen() {
useFirestoreConnect('flashcards')
const projects = useSelector(state => {
state.firestore.data.flashcards
})
console.log(projects)
return(// some ui element)
}
My Question is when I console.log(state.firestore.data.flashcards) I get my data. But when I console.log(projects) I don't get it. Why? And does it have anything to do with redux-thunk?
In order to work, the arrow function in the selector should return some value e.g.
const projects = useSelector(state => {
return state.firestore.data.flashcards
})
Or simply remove the curly brackets
const projects = useSelector(state => state.firestore.data.flashcards)
Related
I have a FlatList component that uses Redux (indirectly) as the source for the data prop. See below
const mapStateToProps = state => ({
rdx_activeUsers: state.profile.activeUsers,
});
convertRdxActiveUsersObjectToUsableArray = () => {
let activeUsersArray = [];
Object.values(this.props.rdx_activeUsers).forEach(userObj => {
activeUsersArray.push(userObj);
});
return activeUsersArray;
};
//-----------------------------------------------------------------------
render() {
let usableArray4FlatList = this.convertRdxActiveUsersObjectToUsableArray();
return (
<View>
<FlatList
data={usableArray4FlatList}
Whenever an active user is added or removed in Firebase DB, I have listeners that increase or reduce the size of the Redux object rdx_activeUsers.......the goal is that this change in Redux should trigger the render() function (due to Redux being used in the convertRdxActiveUsersToUsableArray function....which is present in the render() function).
I can see via debugging tool that Redux rdx_activeUsers object is updating correctly whenever I add or remove a user....however the FlatList only rerenders dynamically when I add a user (i.e. the Redux object rdx_activeUsers increases in size)...but not when I remove one (i.e the Redux object rdx_activeUsers decreases in size).
I also tried adding prop extraData={this.props.rdx_activeUsers} ...but this didnt make any difference
UPDATE AS OF 12/31
Below are my reducers......
case ACTIVE_USER_CHILD_ADDED is successfully updating Redux AND triggering the rerender
case ACTIVE_USER_CHILD_REMOVED is successfully updating Redux BUT NOT triggering the rerender....looks like thats where the issue is
case ACTIVE_USER_CHILD_ADDED:
const key2Add = action.payload.userId;
const val2Add = action.payload;
return { ...state, activeUsers: { ...state.activeUsers, [key2Add]: val2Add } };
case ACTIVE_USER_CHILD_CHANGED:
const key2Updel = action.payload.userId;
const val2Updel = action.payload;
if (val2Updel.active) {
return { ...state, activeUsers: { ...state.activeUsers,[key2Updel]: val2Updel } };
}
if (state.activeUsers) {
const updatedstate = state;
delete updatedstate.activeUsers[key2Updel];
return {...updatedstate};
}
//else
return state;
case ACTIVE_USER_CHILD_REMOVED:
const key2Del = action.payload.userId;
const oldState = state;
delete oldState.activeMsgUsers[key2Del];
return {...oldState};
Below shows my action creators
export const _actActiveUserChildAdded = userObj => {
return {
type: ACTIVE_USER_CHILD_ADDED,
payload: userObj,
};
};
export const _actActiveUserChildChanged = userObj => {
return {
type: ACTIVE_USER_CHILD_CHANGED,
payload: userObj,
};
};
export const _actActiveUserChildRemoved = userObj => {
return {
type: ACTIVE_USER_CHILD_REMOVED,
payload: userObj,
};
};
change case ACTIVE_USER_CHILD_REMOVED like following it should work, you are modifying the object which was mutating the state object instead of returning a new object.
case ACTIVE_USER_CHILD_REMOVED:
const key2Del = action.payload.userId;
const {activeUsers:{[key2Del]:_,...restActiveUsers}} = state;
return {...state,activeUsers:{...restActiveUsers}};
This piece of code does not trigger a rerender
case ACTIVE_USER_CHILD_REMOVED:
const key2Del = action.payload.userId;
const oldState = state;
delete oldState.activeMsgUsers[key2Del];
return {...oldState};
By returning {...oldState} all the references inside this.state stay the same, and no update is triggered
fast solution
Put return {...oldState, activeMsgUsers: {...activeMsgUsers}} instead
better solution
Don't use delete, use Array.filter instead to create a new object reference
best solution
Refactor your conponent to hooks and make activeMsgUsers a standalone state, if you do it correctly, calling setActiveMsgUsers returning the destructured old state you cannot have that problem
try this
const mapStateToProps = state => ({
rdx_activeUsers: state.profile.activeUsers,
});
//-----------------------------------------------------------------------
render() {
let activeUsersArray = [];
Object.values(this.props.rdx_activeUsers).forEach(userObj => {
activeUsersArray.push(userObj);
});
return (
<View>
<FlatList
data={activeUsersArray}
I'm new in react native world and i'm on a new project with store (manage by redux).
I encounter an issue with custom hooks and useEffect
here my custom hooks
const useTheme = () => {
const [activeTheme, setActiveTheme] = useState();
const { id: universID, defaultTheme: universDefaultTheme } = useSelector(
(state) => state.univers
);
const { theme } = useSelector((state) => state);
const { themes: activeThemes } = useSelector((state) => state.settings);
const dispatch = useDispatch();
//set theme when univers change
useEffect(() => {
console.log('TODO TOO MANY CALLS!!!!!', universID);
if (universID) {
setTheme(
activeThemes.find((theme) => theme.univers === universID)?.theme
);
}
}, [universID]);
//get active theme of current univers
useEffect(() => {
setActiveTheme(
activeThemes.find((theme) => theme.univers === universID)?.theme
);
}, [activeThemes]);
... rest of code ...
return {
theme,
activeTheme,
setTheme,
};
}
on components i use
const {
theme: { colors },
} = useTheme();
My issue is that on every import the useEffect(()=>{},[universID]) is trigger. UniversID come from redux store.
If i understand clearly when i import useTheme() the reference of universID change because there are copy of universID from store created, and reference change.
if i pass universID as arguments to useTheme hooks there are no problem, cause reference is the same. But if i do this i need tu make a useSelector(universID) on every components who import useTheme hooks.
My understanding of mecanism is good ?
There are a way to get universID from store with the same reference on every import, for not trigger useEffect(,[universID]) on every import ? without pass universID as arguments of useTheme (i.e. useRef, useCallback) ?
Thanks for the time past to read (or better, to answer ;))
When kept in the component body, the following code works fine. Inside useEffect, it checks the asyncstorage and dispatches an action (the function is longer but other checks/dispatches in the function are of the same kind - check asyncstorage and if value exists, dispatch an action)
useEffect(() => {
const getSettings = async () => {
const aSet = await AsyncStorage.getItem('aSet');
if (aSet) {
dispatch(setASet(true));
}
};
getSettings();
}, [dispatch]);
I'm trying to move it to a custom hook but am having problems. The custom hook is:
const useGetUserSettings = () => {
const dispatch = useDispatch();
useEffect(() => {
const getSettings = async () => {
const aSet = await AsyncStorage.getItem('aSet');
if (aSet) {
dispatch(setASet(true));
}
};
getSettings();
}, [dispatch]);
};
export default useGetUserSettings;
Then in the component where I want to call the above, I do:
import useGetUserSettings from './hooks/useGetUserSettings';
...
const getUserSettings = useGetUserSettings();
...
useEffect(() => {
getUserSettings();
}, [getUserSettings])
It returns an error:
getUserSettings is not a function. (In 'getUserSettings()', 'getUserSettings' is undefined
I've been reading rules of hooks and browsing examples on the internet but I can get it working. I've got ESlint set up so it'd show if there were an invalid path to the hook.
Try the following.
useEffect(() => {
if (!getUserSettings) return;
getUserSettings();
}, [getUserSettings]);
The hook doesn't return anything, so it's not surprising that the return value is undefined ;)
I'm new to hooks and ran across this setup on SO and wanted to confirm that this is the correct pattern. I was getting the RN "unmounted component" leak warning message before and this seemed to solve it. I'm trying to mimic in some way compnentDidMount. This is part of a phone number verify sign up flow and onMount I want to just check for navigation and then fire off a side effect, set mounted true and then unmount correctly.
const SMSVerifyEnterPinScreen = ({ route, navigation }) => {
const [didMount, setDidMount] = useState(false)
const { phoneNumber } = route.params
useEffect(() => {
if(navigation) {
signInWithPhoneNumber(phoneNumber)
setDidMount(true)
}
return () => setDidMount(false)
}, [])
if (!didMount) { return null }
async function signInWithPhoneNumber(phoneNumber) {
const confirmation = await auth().signInWithPhoneNumber('+1'+phoneNumber)
...
}
return (
...
)
}
RN 0.62.2 with react-nav 5 - thanks!
Since signInWithPhoneNumber is a async function and will setState you will see warning it the component is unmounted before the response is available
In order to handle such scenarios you can keep a variable to keep track whether its mounted or not and then only set state is the mounted variable is true
However you do not need to return null if component has unmounted since that doesn't accomplish anything. The component is removed from view and will anyways not render anything.
Also you do not need to maintain this value in state, instead use a ref
const SMSVerifyEnterPinScreen = ({ route, navigation }) => {
const isMounted = useRef(true)
const { phoneNumber } = route.params
useEffect(() => {
if(navigation) {
signInWithPhoneNumber(phoneNumber)
}
return () => {isMounted.current = false;}
}, [])
async function signInWithPhoneNumber(phoneNumber) {
const confirmation = await auth().signInWithPhoneNumber('+1'+phoneNumber)
...
}
return (
...
)
}
I am facing problem exactly like what is mentioned in the link below:
https://github.com/facebook/react-native/issues/8589
Wish to load from AsyncStorage and set a few global variables. Because the rest of the pages depending on those variables.
If I use async await or then() I still can't stop the rest of the pages from rendering before the global variables are set.
I tried to make every component async, but unfortunately I can't get it working as well.
Mainly because of this line:
const _App = (props) => {
return (
<I18nextProvider i18n={i18next}>
<App />
</I18nextProvider>);
}
// registerComponent() can't accept anything that is Async
AppRegistry.registerComponent(appName, () => _App);
Try this
const _App = (props) => {
const [loaded, setLoaded] = useState(false)
useEffect(()=>{
const functionName = async () => {
await registerComponent()
setLoaded(true)
}
functionName()
},[])
if(!loaded) return <View><Text>Some Fancy loading stuff here</Text></View>
return (
<I18nextProvider i18n={i18next}>
<App />
</I18nextProvider>);
}