I am new to Vue.js and experiencing an issue with Vuex modules and Axios. I have a "post" component that retrieves a slug from the router and fetches data with Axios which is then retrieved with Vuex Getters.
I am able to retrieve data successfully but then I still see this error on my DevTools, "TypeError: Cannot read property 'name' of undefined"
Due to this error I am not able to pass this.post.name to Vue-Meta.
Codes
Post.vue
computed: {
...mapGetters(["post"]),
},
mounted() {
const slug = this.$route.params.slug;
this.fetchPost({ slug: slug });
},
methods: {
...mapActions(["fetchPost"]),
/store/modules/post.js
const state = {
post: [],
};
const getters = {
post: (state) => {
return post;
}
};
const actions = {
async fetchPost({ commit }, arg) {
try {
await axios.get("/post/" + arg.slug).then((response) => {
commit("setPost", response.data);
});
} catch (error) {
console.log(error);
}
},
};
const mutations = {
setPost: (state, post) => (state.post = post),
};
export default {
state,
getters,
actions,
mutations,
};
Your getter is utterly wrong: a state getter is supposed to be a function that takes in the entire state as a param and retrieves whatever you're interested in from it. Your version...
const getters = {
post: (state) => {
return post;
}
};
...takes in the state as a param but doesn't use it. Instead, it returns a variable (post) which has not been defined in that context.
Which will always return undefined, regardless of current value of state.post.
And, as you already know, JavaScript can't access property 'name' of undefined.
To get the current value of state.post, use:
const getters = {
post: state => state.post
}
Or
const getters = {
post: (state) => { return state.post; }
}
... if you fancy brackets.
Also, out of principle, I suggest initializing your post with an empty object {} instead of an empty array [].
Changing variable types as few times as possible is a very good coding habit, providing huge benefits in the long run.
Edit (after [mcve])
You have a bigger problem: the import from your axios plugin returns undefined. So you can't call get on it. Because you wrapped that call into a try/catch block, you don't get to see the error but the endpoint is never called.
I don't know where you picked that plugin syntax from but it's clearly not exporting axios. Replacing the import with import axios from 'axios' works as expected.
Another advice would be to namespace your store module. That's going to become useful when you'll have more than one module and you'll want to specifically reference a particular mutation/action on a specific module. You'll need to slightly change mapActions and mapGetters at that point.
See it working here.
Related
For example, could I iterate over Vuex data in a Vue file and choose the data needing updating, then pass the found data to an action, which commits it and then the mutation only makes the update?
The reason I'm unsure about it is because the typical format of a Vuex mutation contains the parameter for 'state', so I assume it needs to be used, and the only way to do that is either by doing all the looping inside the mutation, or to pass indexes to it to more quickly find the exact fields needing changing.
For who asked, a code example:
someVueFile.vue
computed: {
...mapState({
arrayOfObjects: (state) => state.someVuexStore.arrayOfObjects
}),
},
methods: {
myUpdateMethod() {
let toBePassedForUpdate = null;
let newFieldState = "oneValue";
this.arrayOfObjects.forEach((myObject) => {
if (myObject.someDataField !== "oneValue") {
toBePassedForUpdate = myObject.someDataField;
}
})
if (toBePassedForUpdate) {
let passObject = {
updateThis: toBePassedForUpdate,
newFieldState: newFieldState
}
this.$store.dispatch("updateMyObjectField", passObject)
}
}
}
someVuexStore.js
const state = {
arrayOfObjects: [],
/* contains some object such as:
myCoolObject: {
someDataField: "otherValue"
}
*/
}
const mutations = {
updateMyObjectField(state, data) {
data.updateThis = data.newFieldState;
}
}
const actions = {
updateMyObjectField(state, data) {
state.commit("updateMyObjectField", data);
}
}
Yes, it's alright to mutate state passed in through the payload argument rather than state. Vuex doesn't bother to distinguish between the two. In either case, it's the same state, and neither option detracts from the purposes of using mutations.
To feel more sure of that, you can ask what are the purposes of mutations and of enforcing their use. The answer is to keep a centralized, trackable location for concretely defined changes to state.
To illustrate this is a good thing, imagine an app with 1000 components, each one changing state locally, outside of a mutation, and in different ways. This could be a nightmare to debug or comprehend as a 3rd party, because you don't know how or where state changes.
So mutations enforce how and a centralized where. Neither of these are damaged by only using the payload argument in a mutation.
I would do all of the logic from one action, you can desctructured the context object in the action signature like so :
actions: {
myAction ({ state, commit, getters, dispacth } ,anyOtherParameter) {
let myVar = getters.myGetter//use a getter to get your data
//execute logic
commit('myCommit', myVar)//commit the change
}
}
If you need to do the logic in your component you can easily extract the getter and the logic from the action.
I'm getting TypeErrors when using NgRx select functions when accessing nested properties.
I have my root store configured in app.module.ts like this:
StoreModule.forRoot({ app: appReducer }),
where app reducer is just a standard reducer. It sets the state correctly; I can see that in the redux dev tools. The selectors for some nested properties that are erroring are:
const getAppFeatureState = createFeatureSelector<IAppState>('app');
export const getAppConfig = createSelector(getAppFeatureState, state => {
return state.appConfig.data;
});
export const getConfigControls = createSelector(getAppConfig, state => {
console.log({ state }) // logs values from initial state
return state.controls;
});
export const getConfigDropdowns = createSelector(
getConfigControls,
state => state.dropdowns,
);
When I subscribe to these selectors in app.compontent.ts like this
ngOnInit() {
this.store.dispatch(new appActions.LoadAppConfig());
this.store
.pipe(select(appSelectors.getConfigDropdowns))
.subscribe(data => {
console.log('OnInit Dropdowns Data: ', data);
});
}
app.component.ts:31 ERROR TypeError: Cannot read property 'dropdowns' of null
at app.selectors.ts:18
When I add logging to the selectors higher up the chain, I can see that the only elements logged are the initialState values, which are set to null. I don't think this selector function should fire until the value changes from its initial value. But since it doesn't, its unsurprising that I'm getting this error, since it is trying to access a property on null. Is it a necessity that initialState contain the full tree of all potential future nested properties in order not to break my selectors?
How can I prevent this selector firing when its value is unchanged?
Also, Is the StoreModule.forRoot configured correctly? It is somewhat puzzling to me that creating a "root" store, creates the app key in my redux store parallel to my modules' stores, ie, the module stores are not underneath app.
Edit:
Adding general structure of app.reducer.ts. I use immer to shorten boilerplate necessary for updating nested properties, however I have tried this reducer also as the more traditional kind with spread operator all over the place and it works identically.
import produce from 'immer';
export const appReducer = produce(
(
draftState: rootStateModels.IAppState = initialState,
action: AppActions,
) => {
switch (action.type) {
case AppActionTypes.LoadAppConfig: {
draftState.appConfig.meta.isLoading = true;
break;
}
/* more cases updating the properties accessed in problematic selectors */
default: {
return draftState; // I think this default block is unnecessary based on immer documentation
}
}
}
Edit: Add initialState:
const initialState: rootStateModels.IAppState = {
user: null,
appConfig: {
meta: {isError: false, isLoading: false, isSuccess: false},
data: {
controls: {
dropdowns: null,
}
},
},
};
Because you updated your question the answer is https://www.learnrxjs.io/learn-rxjs/operators/filtering/distinctuntilchanged
it allows to emit values only when they have been changed.
store.pipe(
map(state => state.feature.something),
distinctUntilChanged(),
)
requires state.feautre.something to have been changed.
The right way would be to use createSelector function that returns memorized selectors that works in the same way as distinctUntilChanged.
You can use filter operator to make sure it emits values only for valid values, and after that you can use pluck operator to emit value of respective nested property.
store.pipe(
filter(value => state.feature.something),
pluck('feature', 'something'),
)
The dispatch method is async.
So:
ngOnInit() {
this.store.dispatch(new appActions.LoadAppConfig());
this.store
.pipe(select(appSelectors.getConfigDropdowns))
.subscribe(data => {
console.log('OnInit Dropdowns Data: ', data);
});
}
Here the subscription runs faster than the dispatch so the select returns with null value from your initial state. Simply check this in the selector or add initial state. EX:
const getAppFeatureState = createFeatureSelector<IAppState>('app');
export const getAppConfig = createSelector(getAppFeatureState, state => {
return state.appConfig.data;
});
export const getConfigControls = createSelector(getAppConfig, state => {
console.log({ state }) // logs values from initial state
return state.controls;
});
export const getConfigDropdowns = createSelector(
getConfigControls,
state => state ? state.dropdown : null,
);
Ok, I took a look again in code and updated my answer.
Can you try below given sample.
this.store
.pipe(
// Here `isStarted` will be boolean value which will enable and disable selector.
//This can be derived from initial state, if null it wont go to next selector
switchMap(data => {
if (isStarted) {
return never();
} else {
return of(data);
}
}),
switchMap(data => select(appSelectors.getConfigDropdowns))
)
.subscribe(data => {
console.log("OnInit Dropdowns Data: ", data);
});
I'm trying to write a Vue plugin that's a simple abstraction to manage auth state across my app. This will need to access other Vue plugins, namely vuex, vue-router and vue-apollo (at the moment).
I tried extending Vue.prototype but when I try to access the plugin's properties how I would normally - eg. this.$apollo - I get the scope of the object, and therefore an undefined error. I also tried adding vm = this and using vm.$apollo, but this only moves the scope out further, but not to the Vue object - I guess this is because there is no instance of the Vue object yet?
export const VueAuth = {
install (Vue, _opts) {
Vue.prototype.$auth = {
test () {
console.log(this.$apollo)
}
}
}
}
(The other plugins are imported and added via. Vue.use() in the main app.js)
Alternatively, I tried...
// ...
install (Vue, { router, store, apollo })
// ...
but as a novice with js, I'm not sure how this works in terms of passing a copy of the passed objects, or if it will mutate the originals/pass by ref. And it's also very explicit and means more overhead if my plugin is to reach out to more plugins further down the line.
Can anyone advise on a clean, manageable way to do this? Do I have to instead alter an instance of Vue instead of the prototype?
In the plugin install function, you do not have access to the Vue instance (this), but you can access other plugins via the prototype. For example:
main.js:
Vue.use(Apollo)
Vue.use(VueAuth) // must be installed after vue-apollo
plugin.js:
export const VueAuth = {
install (Vue) {
Vue.prototype.$auth = {
test () {
console.log(Vue.prototype.$apollo)
}
}
}
}
I found a simple solution for this issue:
In plugin installer you need to add value to not just prototype, but Vue itself to be able to use it globally.
There is a code example:
Installer:
import apiService from "../services/ApiService";
// Service contains 'post' method
export default {
install(Vue) {
Vue.prototype.$api = apiService;
Vue.api = apiService;
}
};
Usage in other plugin:
import Vue from "vue";
...
const response = await Vue.api.post({
url: "/login",
payload: { email, password }
});
Usage in component:
const response = await this.$api.post({
url: "/login",
payload: { email, password }
});
I'm not sure if that's a good solution, but that made my scenario work perfectly.
So, I got around this by converting my property from a plain ol' object into a closure that returns an object, and this seems to have resolved my this scoping issue.
Honestly, I've jumped into Vue with minimal JS-specific knowledge and I don't fully understand how functions and the likes are scoped (and I'm not sure I want to look under that rock just yet......).
export const VueAuth = {
install (Vue, opts) {
Vue.prototype.$auth = function () {
let apollo = this.$apolloProvider.defaultClient
let router = this.$router
return {
logIn: function (email, password) {
apollo.mutate({
mutation: LOGIN_MUTATION,
variables: {
username: email,
password: password,
},
}).then((result) => {
// Result
console.log(result)
localStorage.setItem('token', result.data.login.access_token)
router.go(router.currentRoute.path)
}).catch((error) => {
// Error
console.error('Error!')
console.error(error)
})
},
logOut: function () {
localStorage.removeItem('token')
localStorage.removeItem('refresh-token')
router.go()
console.log('Logged out')
},
}
}
It's a rudimental implementation at the moment, but it'll do for testing.
I am trying to separate my axios calls from my main vue instance by importing them instead of calling them directly in the created hook.
I have this in a separate file called data.js
import axios from 'axios'
export default{
myData() {
return axios.get(`http://localhost:8080/data.json`)
.then(response => {
// JSON responses are automatically parsed.
return response.data;
})
.catch(e => {
return this.myErrors.push(e)
});
},
And in my vue instance I have the following:
import myDataApi from '#/api/data.js'
export default {
name: 'app',
components: {
myDataApi, // not sure if this is correct
},
data: function () {
return {
myInfo: '',
}
},
created() {
this.myInfo = myDataApi.myData();
console.log('this.myInfo= ', this.myInfo)
},
I am trying to populate myInfo with the json called by myData. This returns [object Promise] in Vue devtools and the as Promise {<pending>} in the console.
All the data I need is inside that Promise {<pending>} in an array called [[PromiseValue]]:Object so I know it is working, I just need to know the correct way implementing this.
I don't have a development environment enabled to test this at the moment, but I do notice that you are trying to assign a variable the moment that the component is initialized. This object is a promise, but you're not handling the promise after it is resolved inside the component where you have imported it.
I would recommend trying to handle the promise inside of the actual component, something like:
import myDataApi from '#/api/data.js'
export default {
name: 'app',
components: {
myDataApi, // not sure if this is correct
},
data: function () {
return {
myInfo: '',
}
},
created() {
myDataApi.myData()
.then((data) => {
this.myInfo = data
console.log('this.myInfo= ', this.myInfo);
});
.catch((e) => handleError) // however you want to handle it
},
Just to add to #LexJacobs answer. I omitted the parenthesis around data in .then() as seen below. Vue was squawking about data not being available even though it was. This solved that problem, although to be honest I don't know why.
myDataApi.myData()
.then(data => {
this.dataHasLoaded = true;
this.myInfo = data;
})
.catch(e => {
this.myErrors.push(e)
});
Fiddle : here
I am creating a webapp with Vue 2 with Vuex. I have a store, where I want to fetch state data from a getter, What I want is if getter finds out data is not yet populated, it calls dispatch and fetches the data.
Following is my Vuex store:
const state = {
pets: []
};
const mutations = {
SET_PETS (state, response) {
state.pets = response;
}
};
const actions = {
FETCH_PETS: (state) => {
setTimeout(function() {
state.commit('SET_PETS', ['t7m12qbvb/apple_9', '6pat9znxz/1448127928_kiwi'])
}, 1000)
}
}
const getters = {
pets(state){
if(!state.pets.length){
state.dispatch("FETCH_PETS")
}
return state.pets
}
}
const store = new Vuex.Store({
state,
mutations,
actions,
getters
});
But I am getting following error:
Uncaught TypeError: state.dispatch is not a function(…)
I know I can do this, from beforeMount of Vue component, but I have multiple components which uses same Vuex store, so I have to do it in one of the components, which one should that be and how will it impact other components.
Getters can not call dispatch as they are passed the state not context of the store
Actions can call state, dispatch, commit as they are passed the context.
Getters are used to manage a 'derived state'.
If you instead set up the pets state on the components that require it then you would just call FETCH_PETS from the root of your app and remove the need for the getter
I know this is an older post and I'm not sure if this is good practice, but I did the following to dispatch from a getter in my store module:
import store from "../index"
And used the store inside my getter like this:
store.dispatch("moduleName/actionName")
I did this to make sure data was made available if it was not already present.
*edit:
I want you to be aware of this: Vue form - getters and side effects
This is related to #storsoc note.
If you need to dispatch from your getter you probably are already implementing your state wrong. Maybe a component higher up should already have fetched the data before (state lifting). Also please be aware that getters should only be used when you need to derive other data from the current state before serving it to your template otherwise you could call state directly: this.$store.state.variable to use in methods/computed properties.
Also thing about your lifecycle methods.. you could for example in your mounted or created methods check if state is set and otherwise dispatch from there. If your getter / "direct state" is inside a computed property it should be able to detect changes.
had the same Problem.. also wanted all Vue-Instances to automaticly load something, and wrote a mixin:
store.registerModule('session', {
namespaced: true,
state: {
session: {hasPermission:{}},
sessionLoaded:false
},
mutations: {
changeSession: function (state, value)
{
state.session = value;
},
changeSessionLoaded: function (state)
{
state.sessionLoaded = true;
}
},
actions: {
loadSession(context)
{
// your Ajax-request, that will set context.state.session=something
}
}
});
Vue.mixin({
computed: {
$session: function () { return this.$store.state.session.session; },
},
mounted:function()
{
if(this.$parent==undefined && !this.$store.state.session.sessionLoaded)
{
this.$store.dispatch("session/loadSession");
this.$store.commit("changeSessionLoaded");
}
},
});
because it loads only one per vue-instance and store and it it inlcuded automaticly in every vue-instance, there is no need to define it in every main-app
I use a getter to configure a dynamic page. Essentially, something like this:
getter: {
configuration: function () {
return {
fields: [
{
component: 'PlainText',
props: {},
setPropsFromPageState: function (props, pageState, store) {
// custom logic
}
}
]
};
}
}
Then in the page component, when I am dynamically setting the props on a dynamic component, I can call the setPropsFromPageState(field.props, this.details, this.$store) method for that component, allowing logic to be set at the config level to modify the value of the props being passed in, or to commit/dispatch if needed.
Basically this is just a callback function stored in the getter that is executed in the component context with access to the $store via it.