i'm facing a problem, i have fetch function fired in saga
const fetchComments = () =>
fetch(url, {
method: 'POST',
})
.then((r) => r.json())
.then((r) => {
console.log('FETCH', r);
//return r;
});
And when i console.log response without returning it, it works fine and i get an object that has a propperty data, propperty items inside data which is an array of objects item f.e., and every item has propperty text which is a string, "10 -/)(:$##2! 20"* in my specific case. Uncommenting return r affects order in items arrays, specifically reverses it, and string in text propperty is being sliced, leaving me with "#2! 20".
I've tried console.trace() in saga, but this did not lead to anything, all executed functions and methods in both cases are the same.
Related
It's been a while since I've used redux so I may be taking the wrong approach here.
I am creating an autocomplete input.
If the input string is over 1 character, it will search a DB table column for possible options that the user can click to set the field.
I have the input field's value attribute tied to the redux store. My problem is there is a visible delay between pressing a key and seeing it show up in the input field, it makes a round trip to the database before your input is reflected in the input field (and store)...
<input
onChange={ (e) => dispatch(searchForProductInputOptions(e.target.value)) }
onFocus={ (e) => dispatch(setFocusForAutocomplete(e.target.name))}
className={css(styles.input)}
name={`${field.name}`}
autoComplete='off'
placeholder={`Search ${field.name}`}
value={ state.product[state.activePane][field.name].name}
/>
Here is the async thunk:
export const searchForProductInputOptions = createAsyncThunk(
'product/searchInput',
async (searchString, thunkAPI) => {
let model = thunkAPI.getState().productReducer.activeField;
if(searchString.length > 1) {
const response = await searchFieldInDatabase({model, searchString});
return response;
} else {
//short circuit this?
return searchString
}
// The value we return becomes the `fulfilled` action payload
}
);
You can see, for the first character I'm just sending the data back -- it's not async. I would like to send the search string back immediately, to update the state, but of course I need the result from the promise as well.
I looked into the .addCase(method.pending) but couldn't find a solution -- I felt like maybe I wasn't doing this right. Do you dispatch two methods from the onChange? What's the preferred method to send back synchronous data and then fire off the async request.
I have a component that renders a table of Inventoried computer equipment. Here is the relevant code for initial render:
let oEquiptByType = reactive({
Laptop: [],
iPad: [],
"Document Camera": [],
"Overhead Projector": [],
Chromebook: [],
Desktop: [],
MacBook: [],
Scanner: [],
});
// ======== Props =========== //
const props = defineProps({
propFormData: {},
});
// Now let's use Stein to retrieve the SS data
// eslint-disable-next-line no-unused-vars
const fetchSheetsData = function () {
const store = new SteinStore(
"https://api.steinhq.com/v1/storages/618e81028d29ba2379044caa"
);
store
.read("HS - Classrooms")
.then((data) => {
scrapDataHSClassrooms.value = data;
emptyRowsRemoved.value.forEach((item) => {
// Let's construct an object that separates equipment by type
// Check if property exists on oEquiptByType object
const exists = Object.prototype.hasOwnProperty.call(
oEquiptByType,
item["Equipment"]
);
// If item(row) is good lets push the row onto the corresponding Object Array
// in oEquiptByType. This will construct an object where each object property corresponds
// to an equipment category. And each oEquiptByType entry is an array where each array
// element is a row from the SS. e.g., oEquiptByType["Laptop"][3] is a row from
// SS and is a laptop.
if (exists) {
oEquiptByType[item["Equipment"]].push(item);
}
});
})
.catch((e) => {
console.error(e);
failure.value = true;
});
};
// =============== Called on component mount =============================== //
onMounted(fetchSheetsData);
The initial render is fine. Now I have a watcher on the prop so when someone submits a new item for the inventory I push that data onto the corresponding object array (ie, a laptop would be pushed onto the oEquiptByType[props.propFormData.Equipment] via oEquiptByType[props.propFormData.Equipment].push(props.propFormData);
// ================================================================ //
// ======================= Watch effects ========================== //
// ================================================================ //
watch(props.propFormData, () => {
// Push the submitted form item onto the reactive
// oEquiptByType object array. This update of Vue state
// will then be injected into DOM and automagically update browser display.
oEquiptByType[props.propFormData.Equipment].push(props.propFormData);
});
This works fine for the first item I add to backend as you can see here with original and then adding first item :
and after first item added (a laptop)
Notice the oEquiptByType[props.propFormData.Equipment] has the new item added. Great.
But now when I add a second item (a MacBook) is added this is resulting state:
Notice the Macbook array has been updated but also the Laptop array's last item has been overwritten with the Mac book entry??? And this behavior continues for any additional items added from a user. I have read docs over and do not see anything that would explain this behavior. I'm hoping maybe someone with more than my limited experience with Vue can help me out. Any additional info needed please let me know. Thanks...
Update:
Put a JSON.Stringify in watch function
Update two:
here is lineage of prop.FormData-
we start in form-modal and emit the form data like:
emit("emiterUIUpdate", formAsPlainObject);
then catch the data in the parent App.vue:
<FormModal
v-show="isModalVisible"
#close="closeModal"
#emiterUIUpdate="updateUI"
>
<DisplayScrap :propFormData="formData" />
const formData = reactive({});
// Method to be called when there is an emiterUIUpdate event emiited
// from form-modal.vue #param(data) is the form data sent from the
// form submission via the event bus. We will then send this data back
// down to child display-scrap component via a prop.
const updateUI = (data) => {
Object.assign(formData, data);
};
and then as posted previous in display-scrap.vue the prop propFormData is defined and watched for in the watch function. hope that helps..
It seems like the watch is getting triggered more often than you expect.
Might be that changes to props.propFormData are atomic and every incremental change triggers changes to the props, which in turn triggers the watch.
Try console logging the value of props.propFormData with JSON.stringify to see what changes are triggering it.
What happens here:
Your form modal emits the emiterUIUpdate event on Ok or Save (button)
Parent takes the object emitted and use Object.assing to copy all properties of emitted object to a formData reactive object. Instead of creating completely new object, you are just replacing the values of all properties of that object all and over again
The formData object is passed by a prop to child component and whenever it changes, it is pushed to target array
As a result, you have a multiple references to same object (formData hold by a parent component) and all those references are to same object in memory. Every Object.assign will overwrite properties of this object and all references will reflect those changes (because all references are pointing to the same object in memory)
Note that this has nothing to do with Vue reactivity - this is simple JavaScript - value vs reference
There is no clear answer to what to do. There are multiple options:
Simplest (and not clearest)
just do not use Object.assign - create new object every time "Save" is clicked
change formData to a ref - const formData = ref({})
replace the value of that ref on emiterUIUpdate event - formData.value = { ...data }
your watch handler in the child will stop working because you are watching props in a wrong way - instead of watch(props.propFormData, () => { use watch(() => props.propFormData, () => {
Better solution
the data should be owned by parent component
when modal emits new data (Save), Parent will just add the newly generated object into a list
share the data with DisplayScraps component using a prop (this can be a simple list or a computed creating object similar to oEquiptByType)
I've always struggled to get my head around Redux-thunk, as it really don't understand what great purpose it serves. For example, here's a random Redux-Thunk example I found from a website:
export const addTodo = ({ title, userId }) => {
return dispatch => {
dispatch(addTodoStarted());
axios
.post(ENDPOINT, {
title,
userId,
completed: false
})
.then(res => {
setTimeout(() => {
dispatch(addTodoSuccess(res.data));
}, 2500);
})
.catch(err => {
dispatch(addTodoFailure(err.message));
});
};
};
It's seemingly simple, addTodo is a function that takes in the title and userId and returns a function with dispatch as a parameter, which then uses dispatch once and then again for the response of the HTTP request. Because in this case Redux-Thunk is being used, you would just do dispatch(addTodo(x,x));
Why would I not just do something like this though?
function addTodo(dispatch, title,userId){
dispatch(addTodoStarted());
axios
.post(ENDPOINT, {
title,
userId,
completed: false
})
.then(res => {
setTimeout(() => {
dispatch(addTodoSuccess(res.data));
}, 2500);
})
.catch(err => {
dispatch(addTodoFailure(err.message));
});
}
Then from anywhere, I can just call addTodo(dispatch, x, x);
Why would I use the Redux-Thunk example over my own?
Here are few points through which i will try to explain why should go with redux-thunk.
Its middle ware so it will make dispatch and state object available in every action you define without touching you component code.
When you pass dispatch function which is either from props or from mapDispatchToProps(react-redux) which creates closure. This closure keeps memory consumed till asyc operation finished.
When ever you want to dispatch any action, after completing or in async operation you need to pass dispatch function and in this case you need to modify two files like your component and actions.
If something is already available and tested with lot effort and community support why not use it.
your code will be more readable and modular.
Worst case for both approach, say after completing project, need to change thunk approach, you can easily mock thunk middle ware with your custom middle ware code and resolve it but in case of passing dispatch function it will refactoring all code and search and replace and find way to manage it.
In one of my vuex modules I'm loading data 3 times step by step with 3 different API requests using then():
actions: {
loadRoamingHistory: function loadRoamingHistory(context, roamingFilter): Promise<Array<RoamingHistoryEvent>> {
return new Promise((resolve) => {
store.dispatch('network/loadNetworks').then(() => {
store.dispatch('country/loadCountries').then(() => {
providerApi.loadRoamingHistory(roamingFilter).then(data => {
// read already loaded networks and countries from store
let networks = context.rootState.network.networks;
let countries = context.rootState.country.countries;
// .. some data processing using informations from
// networks and countries request, that are not allways available at this point..
console.log('data processing');
commitSetRoamingHistoryEvents(context, data.roamingHistoryEvent);
resolve();
}).catch(err => console.log(err));
});
});
});
}
}
I also added console.log() commands to the network and country vuex setters in order to see what is executed first:
mutations: {
setNetworks: function setNetworks(state: NetworkState, networks: Array<Network>) {
console.log('networks loaded');
state.networks = networks;
},
I would expect the 3 requests to be executed one by one, but the log messages shows that sometimes it is executed in different order, for example log messages goes like this:
networks loaded
countries loaded
networks loaded
data processing
countries loaded
Notice that data processing should be last log, otherwise I cannot process the data correctly. Why it is executed in random order and what could be done in order to fix it?
first of all, I need to correct myself, dispatch is an action, it is asynchronous, so you're correct to use promises with them. (I'm used to mapping actions, so I don't see them much)
anyway, the point of promises was to alleviate the "callback hell". so if your structure is nested like this:
action
action
action
action
you're defeating the point of using a promise in the first place.
Instead the point is to chain them in a readable fashion like so
action
action
action
action
actions: {
loadRoamingHistory: function loadRoamingHistory(context, roamingFilter): Promise<Array<RoamingHistoryEvent>> {
return store.dispatch('network/loadNetworks')
.then(() => {
return store.dispatch('country/loadCountries')
})
.then(() => {
return providerApi.loadRoamingHistory(roamingFilter)
})
.then(data => {
// read already loaded networks and countries from store
let networks = context.rootState.network.networks;
let countries = context.rootState.country.countries;
// .. some data processing using informations from
// networks and countries request, that are not allways available at this point..
console.log('data processing');
return commitSetRoamingHistoryEvents(context, data.roamingHistoryEvent);
})
.catch(err => console.log(err));
}
}
note that...
- the initial promise is not defined. Because the dispatch is asynchronous, it already creates a promise, we just add additional calls to it.
- when returning a promise inside a promise, the next then() will handle it, whether it is withing this function or outside of it
- your catch at the end will log an error anywhere along the chain of promises
I have the following function that validates that rangeFrom is not superior to rangeTo and that the rangeFrom does not already exist in the list of ranges.
How can rewrite this using RxJS?
const isTagAlreadyExist = (tags, currentTag) => _(tags)
.filter(x => x.id !== currentTag.id)
.some(x => _.inRange(currentTag.rangeTo, x.rangeFrom, x.rangeTo))
.value();
const validateRangeFrom = (tags, currentTag) => {
const errors = {};
if (isNumeric(currentTag.rangeFrom)) {
if (!_.inRange(currentTag.rangeFrom, 0, currentTag.rangeTo)) {
errors.rangeFrom = 'FROM_TAG_CANNOT_BE_GREATER_THAN_TO_TAG';
} else if (isTagAlreadyExist(tags, currentTag)) {
errors.rangeFrom ='TAG_ALREADY_EXISTS';
}
}
return {
errors
};
};
The question is: what parts do you want to rewrite to rxjs? Those are two pure functions that run synchronously from what I can see, I do not really see much a usecase for rxjs here - of course you could always utilize your functions within an rxjs stream:
const validateRangeFrom$ = (tags, currentTag) => {
return Observable.of(currentTag)
.map(tag => validateRangeFrom(tags, tag));
}
validateRangeFrom$(myTags, currentTag)
.subscribe(errors => console.log(errors));
But as you can see, this does not make much sense if you simply wrap it inside a stream, the essence of useful reactive programming is, that everything is reactive, not just some small parts, so for your example, you should start with having tags$ and currentTag$ as observables - let's assume that you have that, then you could do something like:
const tags$: Observable<ITag[]>... // is set somewhere, and emits a new array whenever it is changed
const currentTag$: Observable<ITag>... // is set somewhere and emits the tag whenever a new currentTag is set
const validateRangeFrom$ = Observable
.combineLatest(tags$, currentTag$, (tags, tag) => ({tags, tag}))
.map(({tags, tag}) => validateRangeFrom(tags, tag));
validateRangeFrom$.subscribe(errors => console.log(errors));
This will automatically trigger the validation for you whenever a new tags-array is emitted or a new currentTag is selected/set - but again: your validation-method is kept the same - as even in reactive programming you have to do validation and logic-operations at some point, the reactive part usually just concerns the flow of the data (see: tags$ and currentTag$)