Given a reducer example like the following
_({
expandAbility: (state, a: { which: string }) => ({
...state,
report: state.report && {
waitingForIt: false,
content: state.report.content && {
...state.report.content,
interaction: {
expandAbilities: !state.report.content.interaction.expandAbilities.contains(a.which)
? state.report.content.interaction.expandAbilities.add(a.which)
: state.report.content.interaction.expandAbilities.remove(a.which)
}
}
}
}),
})
(state type given below just for question context purposes)
const initialState = {
report: undefined as
| {
waitingForIt?: boolean
content?: {
supportedFightIds: number[]
deathCut: number
reportInfo: any
deathsFull: any
deathsByPlayer: any
deathsByAbility: any
interaction: {
expandAbilities: Set<string>
}
}
}
| undefined,
error: undefined as Error | undefined
}
Is there any kind of trick or "flavor-of-the-moment" library which would allow me to write a reducer update operation like expandAbility in a shorter way? (besides maybe creating some vars to reference inner paths)
There are lots of immutable update utilities out there, check out some options at https://github.com/markerikson/redux-ecosystem-links/blob/master/immutable-data.md#immutable-update-utilities and see what would be the best fit for you.
For starters check out Immutability-helper or immer.
So there are two things you could do to help simplify this. The first thing I like to do is move the logic out of the reducer and instead just pass in a value and say set expandAbilities to action. expandAbilities.
The second is actually something we do at work. We use immutableJS and wrote a single reducer that handles all of our state calls because you can give it a path of the parts of state that need to be updated and the value to update it with so we extracted that out and now it is easy to say dispatch(actions.update({path: ['report', 'content', 'interaction', 'expandAbilities'], value: '123' }))
You can even expand this so you can pass in a list of values that need to be updated and even preform validations around the data.
Related
I have an object in my redux state
const obj = {
name: 'name',
age: 2,
place: 0,
}
I show these values on the page but I want to make two of them editable so that the object can be updated.
For that I'm basically getting values from two inputs and sending them to my action
export const saveEditedData = data => dispatch => {
dispatch({
type: CHANGE_DATA,
data,
});
}
and then in reducer
case 'CHANGE_DATA':
return {
...state,
obj: {
...state.obj,
name: action.data.name,
age: action.data.age,
}
}
The problem that I'm facing is that if one value is updated and another is not then after this action my second value in empty.
My question is what is a good way to determine which field is changed and update only it?
So far I only came up with putting if else in action to dispatch certain thing. Maybe there is a better way?
You can 1. make each field update with individual actions, changeName, changeAge, etc, or 2. filter the action payload to get rid of the unwanted values before putting them in your obj:
case 'CHANGE_DATA':
return {
...state,
obj: {
...state.obj,
...action.data.filter(el => !!el)
}
}
(the !! notation is converting the array elements to booleans when filtering, not strictly necessary but sanitary)
EDIT: Sorry I misunderstood your data shape, see comments.
I have a query called GET_ME and another one called GET_USER_NOTIFICATIONS. Second one it's looking for user id which will come from first query. My problem is that sometimes I receive [TypeError: undefined is not an object (evaluating 'o.props.getMe.me._id')]
Here is my code for this:
export default compose(
withApollo,
graphql(GET_ME, { name: "getMe" }),
graphql(GET_USER_NOTIFICATIONS, {
name: "notification",
skip: props => !props.getMe || !props.getMe.me,
options: props => ({
variables: { r_id: props.getMe.me._id }
})
})
)(Notifications);
Any help?
Can you try doing:
variables: { r_id: props.getMe && props.getMe.me ? props.getMe.me._id : null }
// I use "null" in case the object doesn't exists.
// You can use value that your graphql needs.
(you could also use lodash for simplicity _.get(...))
The error suggests that it's executing the variables assignment although you have set the query to be skipped. But at the time of the assignment either getMe or getMe.me is "undefined".
If that doesn't help, you can use the Render props Apollo components inside of the render method. That way, you can guarantee you can't set the variable without getting access to getMe.me._id.
Let's say, I have a state that looks as follows.
constructor(props) {
super(props);
this.state = {
setting_a: "value-1",
setting_b: "color-green"
}
}
When I change the state of a specific setting (e.g. setting_a), I don't want other settings (e.g. setting_b) to disappear. So I also specify the other settings while changing the state. (which is easy using the spread operator ...state).
this.setState( {...this.state, setting_a: "value-2"});
I noticed though, that some tutorials restate them, and others only specify the changed key-values.
Things got just a little bit more complicated since the introduction of the Component#getDerivedStateFromProps method, ( since React 16.3 ).
static getDerivedStateFromProps(props, state) {
const oldSetting = state.setting_a;
const newSetting = props.setting_a;
if (oldSetting !== newSetting) {
// this is a very similar situation.
return ({ ...state, state.setting_a: props.setting_a});
}
return null;
}
Again, in the above example, I add all previous settings (i.e. ...state), because I don't want the other settings to be removed.
In both these cases, the same question: do I need to specifically repeat values which are already in the state ? Or are the states always merged incrementally, without removing ?
You don't need to copy the state (using spread operator or any idea) when updating the state with setState. The setState method updates the required state only:
this.setState( {setting_a: "value-2"});
So, now you will still get:
state = {
setting_a: "value-2",
setting_b: "color-green"
}
Similarly, it works like that when you return the object in getDerivedStateFromProps. The returned value is applied in the state without mutation.
You only need to copy the state when you want to update the property of state. For eg.:
// initial state
this.state = {
settings: {
a: 'value-1',
b: 'color-green'
}
}
Now, we have a and b property in settings state. So now, if you wanted to update the a, then you'll need to copy the settings:
this.setState((state) => ({settings: {...state.settings, a: 'value-2' } }))
The preceding example is with settings object. You can think similar with array of state. You may just do a google search for how to update the array without mutation?
It depends.
In your first case you could do:
this.setState( prevState => {
prevState.setting_a = "value-2";
return prevState
});
Or just go with:
this.setState({ setting_a: "value-2" });
As per React Docs State Updates are Merged.
As I understand it, when an action is called, all reducers respond. If action exists in the switch case statement of the reducer, it executes. If it doesn't, then the case: default executes which preserves the existing state.
When the action exists in the reducer but the particular property it's trying to update does not exist, it seems to behave OK as there's nothing to update.
For example, I have an action creator that is used to set the visible property of my modals. Each modal has its own Id. My code looks like this:
export default (state = initialState, action) => {
case types.SET_MODAL_IS_VISIBLE:
return Object.assign({}, state,
{ modal22: action.value }
)}
I have the SET_MODAL_IS_VISIBLE in multiple reducers but if modal22 is not defined in a particular reducer, nothing happens and no errors.
Now, I have a scenario that is throwing an error. I have a general purpose date picker component that I built that can be used as a single and independent date picker OR it can be "linked to" another one. The second scenario is useful if I need the user to give me two dates e.g. start and end dates.
I also built a feature where if the date picker is coupled with another one, when the user sets the date in the first date picker, I disable all the dates prior to that date in the second date picker because I don't want the user to unintentionally select an end date that is prior to the start date.
I define my date pickers as below:
const initialState = {
datePickers: {
"startDatePicker": {
activeDate: "8/25/2017",
disabledBefore: "",
linkedTo: "endDatePicker"
},
"endDatePicker": {
activeDate: "",
disabledBefore: "8/25/2017" // This date is set when the user sets the active date in startDatePicker
linkedTo: ""
}
}
}
This scenario is a bit interesting because a state change in one property in my reducer is triggering a state change in another. This is not difficult to do and I have a way of controlling when I do the update.
The action for setting disabled dates looks like below:
...
case types.SET_DISABLED_DATES:
return Object.assign({}, state,
datePickers: Object.assign({}, state.datePickers, {
datePickers[action.datePickerId]: Object.assign({}, state.datePickers[action.datePickerId], {
disabledBefore: action.value
})
})
Please keep in mind that I can and should be able to set disabledBefore even if the date picker is used as an independent one. So, I need my SET_DISABLED_DATES in every reducer.
The problem I'm running into is that whenever I call SET_DISABLED_DATES, I get errors in reducers where the date picker is used as a single/independent one because the date picker Id for its pair is NOT defined in the reducer.
For example, in projectsReducer I may use the date picker as part of a pair so both startDatePicker and endDatePicker are defined and everything works fine.
But I may be using a single instance date picker in the tasksReducer which also responds to the SET_DISABLED_DATES call but it fails because it cannot find the endDatePicker. In this scenario, the tasksReducer is responding to the call I made to set the disabledDates property of endDatePicker in projectsReducer.
I've posted two questions about this already and the only real solution I'm seeing here is that I need to have a condition in my reducer that looks like this:
...
case types.SET_DISABLED_DATES:
if(typeof state.datePickers[action.datePickerId] !== "undefined") { // Making sure that what I'm trying to update exists in the reducer
return Object.assign({}, state,
datePickers: Object.assign({}, state.datePickers, {
datePickers[action.datePickerId]: Object.assign({}, state.datePickers[action.datePickerId], {
disabledBefore: action.value
})
})
} else {
return state;
}
Admittedly, this looks a bit like a kludge but I couldn't really come up with another solution here.
Again, the problem is that for as long as all reducers respond to SET_DISABLED_DATES, it's guaranteed that a particular date picker will not be there and the Object.assign() will throw an error.
Any suggestions? Is the simple condition in the reducer the way to go here? Is it a kludge?
P.S. I tried this code and it works fine and fixes the problem. On the one hand, I feel this is a bit of an anti-pattern but on the other hand, it just seems like a good idea to make sure the property I want to update in my reducer exists before attempting to update it. I'd appreciate your feedback on this. Thanks.
You are just doing basic validation in the reducer before setting the state. That is perfectly fine. I don't think it will be a good practice to check the store in the action creator to prevent dispatching actions on objects not in the store (how would you do that anyway!).
What I don't understand is, how can a datepicker be linked to another datepicker that isn't in the store? Maybe dispatch a create and teardown action on the component's didMount and willUnmount?
I don't know your full requirements but I think we can make it a lot simpler. I'd do something like this:
The store:
{
datePickers: {
id1: {
value: '',
minValue: '',
maxValue: '',
},
id2: {
value: '',
minValue: '',
maxValue: '',
}
}
}
Now, unless you are making some kind of coupled datepicker components that will always behave in pairs, I believe the cleanest approach would be to set the disabled value in the linked datepicker in the mapDispactchToProps function in your parent component.
That is where you would set ids to the components, and you know exactly which component should be disabled before another.
Something like:
dispatch => ({
setArrivalDate(value) {
dispatch(datePickerActions.setValue(arrivalDateId, value);
dispatch(datePickerActions.setMaxValue(depatureDateId, value);
},
setDepatureDate(value) {
dispatch(datePickerActions.setValue(depatureDateId, value);
dispatch(datePickerActions.setMinValue(arrivalDateId, value);
}
})
This may not be abstract enough, but is clean.
You could do the same thing if you have a paired component, but you'd still need to know which date comes before another. It'd be a hassle to make a generic abstraction around it.
Remove the bold part in your code below
...
case types.SET_DISABLED_DATES:
if(typeof state.datePickers[action.datePickerId] !== "undefined") { // Making sure that what I'm trying to update exists in the reducer
return Object.assign({}, state,
datePickers: Object.assign({}, state.datePickers, {
datePickers[action.datePickerId]: Object.assign({}, state.datePickers[action.datePickerId], {
disabledBefore: action.value
})
})
} else {
return state;
}
Also, a little bit of es6 spread and a helper switchcase function makes this code much more readable.
const newReducer = (state = defaultState, action) => switchcase({
[types.SET_DISABLED_DATES]:
state.datePickers[action.datePickerId] === undefined
? state
: ({ ...state,
datePickers: { ...state.datePickers,
[action.datePickerId]: { ...state.datePickers[action.datePickerId],
disabledBefore: action.value,
},
},
}),
})(state)(action.type);
Using lodash/fp/set, the code becomes
const reducerWithLodash = (state = defaultState, action) =>
switchcase({
[types.SET_DISABLED_DATES]:
state.datePickers[action.datePickerId] === undefined
? state
: set({...state}, `datePickers.${action.datePickerId}.disabledBefore`, action.value)
})(state)(action.type)
I haven't tested the lodash version, so please take that with a grain of salt (Dan Abramov seems to approve)
I've an confusion. I'm trying to add array variable in setState. My code is working properly but wanted to confirm some doubt before committing my code.
Which is right way to store array in state variable ?
var names = ['Jake', 'Jon', 'Thruster'];
this.setState({
state: names
});
Or
this.setState((state) => {
state.items.push(names[0]);
return state;
});
What is necessary of return statement here ?
Can some one please explain me the difference here ? I searched in google but I'm still confused.
var names = ['Jake', 'Jon', 'Thruster'];
this.setState({
names //according to Airbnb rules
});
or
this.setState({
names: names
});
this.state.names = ['Jake', 'Jon', 'Thruster'];
setState takes a second argument - callback, that will called after setting State properties
setState({property1: value1, ...}, () => { //some code after State changed })
The first approach is much more common and in my opinion, easier to read. The issue with your code is you don't need to use the key state, because the function you are calling is "setting state". The key should be something like firstNames.
this.setState({
firstNames: names
});
You could also just pass the object in the function like this because setState takes an object as a parameter.
var namesObject = {
firstNames: names
}
this.setState(namesObject);
I would read more about it here and keep doing small tutorials on this an you'll get the hang of it.
https://facebook.github.io/react/docs/react-component.html#setstate