I have an array of users in my store set up like this:
{users: {user_id: 1, user_name: Adam, user_score: 100},
{user_id: 2, user_name: Bob, user_score: 200},
{user_id: 3, user_name: Charlie, user_score: 300}}
My project is receiving JSON data from the server that is set up like this:
{user_id: 1, score: 10}
I want to find where the user_id of the passed data matches the existing user set's user_id and update the score to the score that was passed in.
For example, if the reducer receives {user_id:2, score:10} how do I change the score to 10 where the user id equals 2 in the original state. While avoiding mutation, of course!
What would be the best way to use do this? Normalizr? Lodash? update()?
Seems pretty simple, I must be missing something obvious here.
Thanks.
I would suggest using immutable.js for this purpose.
Pass the id of the user which you want to update to the action and from there pass it to the reducer and use immutable to update the user data.
So you code in immutable would be something like
const data = Immutable.fromJS(state)
const newState = data.setIn(['users', user_id, 'score'], 10);
return newState.toJS()
P.S: I havent tested the above but it should work(if not modify a little)
You can read about immutable here.
Also I would suggest going through a similar answer here
In your reducer, you can iterate through the existing users array and set a new value for the one that matches the user_id.
function usersReducer(state = [], action) {
switch (action.type) {
case 'UPDATE_SCORE':
var { user_id, score } = action
return state.map(u => {
if (u.user_id === user_id) {
// for the matching user, return an
// object with the updated score
return Object.assign({}, u, { score })
} else {
// for all other users, return the
// existing object
return u
}
})
default:
return state
}
}
Related
I'm making a kind of twitter-style clone using React and Redux. I currently have an object of posts ("lings"), that each contain a nested object of replies. They look like this:
{
id: 5,
userName: "Gordon Maloney",
lingBody: "this is a ling",
lingRepliesObj: [
{
replyId: 0,
replyBody: "this is a reply",
},
{
replyId: 1,
replyBody: "this is a second reply",
},
],
},
I'm trying to build an action that allows users to add a reply, by adding to that nested object. The action pushes the ID of the post being replied to, and then the reply itself - when I console log them, it comes through fine, but I just cannot for the life of me work out:~
a) how to be adding to the right item in the object - it's being passed to the action as "parentId" - but I can't work out how to get it from there into the action reducer
b) I am also definitely doing something wrong trying to add the action payload into the array itself.
The action reducer looks like this (currently just pushing the array index of 5 arbitrarily, but that's what I'm wanting to replace with the parentId)
case ActionTypes.POST_REPLY:
console.log(...state.lings[5].lingRepliesObj);
console.log(action.payload);
return {
...state,
lings: [...state.lings[5].lingRepliesObj, {...action.payload}],
};
And the action itself like this:
export const postReply = (values) => {
console.log("You posted a new reply: ", values);
return {
type: "POST_REPLY",
payload: {
replyId: "new-id",
replyAuthor: "reply tester",
replyType: "correction",
correctionBody: values.replyCorrection,
replyBody: values.replyReply,
},
};
};
Am I even close? 😣
My GitHub for it is here: https://github.com/gordonmaloney/Lingr and the relevant files are:
src/components/actions/newReplyAction
src/components/reducers/lings
src/components/LingReply
I have an array of 6 objects which have a uid and nothing else. This is so I can repeat over them and have some placeholder content until an object is ready to be added into the array. I set a unique key when a new object is selected. However if I select the same object twice, even though I'm setting a unique key. It seems to update the unique key on the duplicate item (even though the unique key is different).
Might be easier to see the code/app in action here, an example of the problem would be clicking squirtle then blastoise, take a note of the uid's shown. Then click squirtle again and for some reason it updates the old squirtle with the new squirtles uid causing a duplicate key error. https://codesandbox.io/s/l75m9z1xwq or see code below. Math.random is just placeholder until I can get this working correctly.
const initState = {
party: [
{ uid: 0 },
{ uid: 1 },
{ uid: 2 },
{ uid: 3 },
{ uid: 4 },
{ uid: 5 }
]
};
When I click on something this is triggered:
handleClick = pokemon => {
// setup a uid, will need a better method than math.random later
pokemon.uid = Math.random();
this.props.addToParty(pokemon);
};
This then calls a dispatch which triggers the following reducer. Which essentially just checks if the object has no normal ID then replace the content with the payload sent over. It does this but also somehow updates any previous objects with the same uid even though the if statement does not run against them.
const rootReducer = (state = initState, action) => {
if (action.type === "ADD_POKEMON") {
let foundFirstEmptyPoke = false;
const newArray = state.party.map((pokemon, index) => {
if (typeof pokemon.id === "undefined" && foundFirstEmptyPoke === false) {
foundFirstEmptyPoke = true;
pokemon = action.payload; // set the data to the first object that ios empty
}
// if we get to the last pokemon and it's not empty
if (index === 5 && foundFirstEmptyPoke === false) {
pokemon = action.payload; // replace the last pokemon with the new one
}
return pokemon;
});
return {
party: newArray
};
}
return state;
};
The problem here is that, when you click to select a pokemon, you mutate the data you retrieved from the API:
handleClick = pokemon => {
pokemon.uid = Math.random(); // HERE
this.props.addToParty(pokemon);
};
You actually mutate the react state. What you should do is clone your pokemon data object, add an uid to the clone you just generated and update your redux state with it:
handleClick = pokemon => {
this.props.addToParty({
...pokemon,
uid: Math.random()
});
};
That way, no references to the actual react state are kept. Because that was what was happening when you say it updates the old squirtle with the new squirtles uid. When you tried to add another pokemon, you updated the data you retrieved from your API which was also referenced from your first pokemon slot (from your redux state).
In react/redux it's always better to not mutate objects:
this.props.addToParty({...pokemon, uid: Math.random()});
You are mutating the state. Use spread syntax *** to copy the state before updating.
return {
...state,
party: newArray
}
I wrote simple reducer for User entity, and now I want to apply best practices for it, when switching action types and returning state. Just to mention, I extracted actions types in separate file, actionsTypes.js.
Content of actionsTypes.js :
export const GET_USERS_SUCCESS = 'GET_USERS_SUCCESS';
export const GET_USER_SUCCESS = 'GET_USER_SUCCESS';
export const ADD_USER_SUCCESS = 'ADD_USER_SUCCESS';
export const EDIT_USER_SUCCESS = 'EDIT_USER_SUCCESS';
export const DELETE_USER_SUCCESS = 'DELETE_USER_SUCCESS';
First question, is it mandatory to have actions types for FAILED case? For example, to add GET_USERS_FAILED and so on and handle them inside usersReducer?
Root reducer is:
const rootReducer = combineReducers({
users
});
There is code of usersReducer, and I put comments/questions inside code, and ask for answers (what are best practices to handle action types):
export default function usersReducer(state = initialState.users, action) {
switch (action.type) {
case actionsTypes.GET_USERS_SUCCESS:
// state of usersReducer is 'users' array, so I just return action.payload where it is array of users. Will it automatically update users array on initial state?
return action.payload;
case actionsTypes.GET_USER_SUCCESS:
// What to return here? Just action.payload where it is just single user object?
return ;
case actionsTypes.ADD_USER_SUCCESS:
// what does this mean? Can someone explain this code? It returns new array, but what about spread operator, and object.assign?
return [...state.filter(user => user.id !== action.payload.id),
Object.assign({}, action.payload)];
case actionsTypes.EDIT_USER_SUCCESS:
// is this ok?
const indexOfUser = state.findIndex(user => user.id === action.payload.id);
let newState = [...state];
newState[indexOfUser] = action.payload;
return newState;
case actionsTypes.DELETE_USER_SUCCESS:
// I'm not sure about this delete part, is this ok or there is best practice to return state without deleted user?
return [...state.filter(user => user.id !== action.user.id)];
default:
return state;
}
}
I'm not an experienced developer but let me answer your questions what I've learned and encountered up to now.
First question, is it mandatory to have actions types for FAILED case?
For example, to add GET_USERS_FAILED and so on and handle them inside
usersReducer?
This is not mandatory but if you intend to give a feedback to your clients it would be good. For example, you initiated the GET_USERS process and it failed somehow. Nothing happens on client side, nothing updated etc. So, your client does not know it failed and wonders why nothing happened. But, if you have a failure case and you catch the error, you can inform your client that there was an error.
To do this, you can consume GET_USERS_FAILED action type in two pleases for example. One in your userReducers and one for, lets say, an error or feedback reducer. First one returns state since your process failed and you can't get the desired data, hence does not want to mutate the state anyhow. Second one updates your feedback reducer and can change a state, lets say error and you catch this state in your component and if error state is true you show a nice message to your client.
state of usersReducer is 'users' array, so I just return
action.payload where it is array of users. Will it automatically
update users array on initial state?
case actionsTypes.GET_USERS_SUCCESS:
return action.payload;
This is ok if you are fetching whole users with a single request. This means your action.payload which is an array becomes your state. But, if you don't want to fetch all the users with a single request, like pagination, this would be not enough. You need to concat your state with the fetched ones.
case actionsTypes.GET_USERS_SUCCESS:
return [...state, ...action.payload];
Here, we are using spread syntax.
It, obviously, spread what is given to it :) You can use it in a multiple ways for arrays and also objects. You can check the documentation. But here is some simple examples.
const arr = [ 1, 2, 3 ];
const newArr = [ ...arr, 4 ];
// newArr is now [ 1, 2, 3, 4 ]
We spread arr in a new array and add 4 to it.
const obj = { id: 1, name: "foo, age: 25 };
const newObj = { ...obj, age: 30 };
// newObj is now { id: 1, name: "foo", age: 30 }
Here, we spread our obj in a new object and changed its age property. In both examples, we never mutate our original data.
What to return here? Just action.payload where it is just single user
object?
case actionsTypes.GET_USER_SUCCESS:
return ;
Probably you can't use this action in this reducer directly. Because your state here holds your users as an array. What do you want to do the user you got somehow? Lets say you want to hold a "selected" user. Either you can create a separate reducer for that or change your state here, make it an object and hold a selectedUser property and update it with this. But if you change your state's shape, all the other reducer parts need to be changed since your state will be something like this:
{
users: [],
selectedUser,
}
Now, your state is not an array anymore, it is an object. All your code must be changed according to that.
what does this mean? Can someone explain this code? It returns new
array, but what about spread operator, and object.assign?
case actionsTypes.ADD_USER_SUCCESS:
return [...state.filter(user => user.id !== action.payload.id), Object.assign({}, action.payload)];
I've already tried to explain spread syntax. Object.assign copies some values to a target or updates it or merges two of them. What does this code do?
First it takes your state, filters it and returns the users not equal to your action.payload one, which is the user is being added. This returns an array, so it spreads it and merges it with the Object.assign part. In Object.assign part it takes an empty object and merges it with the user. An all those values creates a new array which is your new state. Let's say your state is like:
[
{ id: 1, name: "foo" },
{ id: 2, name: "bar" },
]
and your new user is:
{
id: 3, name: "baz"
}
Here what this code does. First it filters all the user and since filter criteria does not match it returns all your users (state) then spread it (don't forget, filter returns an array and we spread this array into another one):
[ { id: 1, name: "foo"}, { id: 2, name: "bar" } ]
Now the Object.assign part does its job and merges an empty object with action.payload, a user object. Now our final array will be like this:
[ { id: 1, name: "foo"}, { id: 2, name: "bar" }, { id: 3, name: "baz" } ]
But, actually Object.assign is not needed here. Why do we bother merging our object with an empty one again? So, this code does the same job:
case actionsTypes.ADD_USER_SUCCESS:
return [...state.filter(user => user.id !== action.payload.id), action.payload ];
is this ok?
case actionsTypes.EDIT_USER_SUCCESS:
const indexOfUser = state.findIndex(user => user.id === action.payload.id);
let newState = [...state];
newState[indexOfUser] = action.payload;
return newState;
It seems ok to me. You don't mutate the state directly, use spread syntax to create a new one, update the related part and finally set your state with this new one.
I'm not sure about this delete part, is this ok or there is best
practice to return state without deleted user?
case actionsTypes.DELETE_USER_SUCCESS:
return [...state.filter(user => user.id !== action.user.id)];
Again, it seems ok to me. You filter the deleted user and update your state according to that. Of course there are other situations you should take into considiration . For example do you have a backend process for those? Do you add or delete users to a database? If yes for all the parts you need to sure about the backend process success and after that you need to update your state. But this is a different topic I guess.
I'm very new to Redux, and confused as to how to update nested state.
const initialState = {
feature: '',
scenarios: [{
description: '',
steps: []
}]
}
I know that to just push to an array in an immutable way, we could do,
state = {
scenarios: [...state.scenarios, action.payload]
}
And to push into a specific attribute, as this SO answer suggests
How to access array (object) elements in redux state, we could do
state.scenarios[0].description = action.payload
But my question is, how would we access a particular attribute in an object array without mentioning the index? is there a way for us to push it to the last empty element?
All suggestions are welcome to help me understand, thank you in advance :)
Redux helps to decouple your state transformations and the way you render your data.
Modifying your array only happens inside your reducers. To specify which scenario's description you want to modify is easy to achieve by using an identifier. If your scenario has in id, it should be included in your action, e.g.
{
"type": "update_scenario_description",
"payload": {
"scenario": "your-id",
"description": "New content here"
}
}
You can have a reducer per scenario. The higher level reducer for all scenarios can forward the action to the specific reducer based on the scenario id, so that only this scenario will be updated.
In your ui, you can use the array of scenarios and your scenario id to render only the specific one you're currently viewing.
For a more detailed explanation, have a look at the todo example. This is basically the same, as each todo has an id, you have one reducer for all todos and a specific reducer per todo, which is handled by it's id.
In addition to the accepted answer, I'd like to mention something in case someone still wants to "access a particular attribute in an object array without mentioning the index".
'use strict'
const initialState = {
feature: '',
scenarios: [{
description: '',
steps: []
}]
}
let blank = {}
Object.keys(initialState.scenarios[0]).map(scene => {
if (scene === 'steps'){
blank[scene] = [1, 2]
} else {
blank[scene]=initialState.scenarios[0][scene]
}
})
const finalState = {
...initialState,
scenarios: blank
}
console.log(initialState)
console.log(finalState)
However, if scenarios property of initialState instead of being an object inside an array, had it been a simple object like scenarios:{description:'', steps: []}, the solution would have been much simpler:
'use strict'
const initialState = {
feature: '',
scenarios: {
description: '',
steps: []
}
}
const finalState = {
...initialState,
scenarios: {
...initialState.scenarios, steps: [1, 2, 4]
}
}
console.log(initialState)
console.log(finalState)
I have an immutable List that looks like this:
this.state = {
suggestedUsers: fromJS([
{
user: {
client_user_id: "1234567890",
full_name: "marty mcfly",
image: "imageURL",
role_name: "Associate Graphic Designer",
selected: false
}
},
{
user: {
client_user_id: "0987654321",
full_name: "doc",
image: "imageURL",
role_name: "Software Engineer",
selected: false
}
}
)]
This is used in a div that displays this information in the UI.
When I click on the div, I have a function that is fired that looks like this:
selectUser(clientUserId){
// set assessments variable equal to the current team from the state
let assessments = fromJS(this.state.suggestedUsers)
let selectAssessor
// set a variable called selectedUsers equal to the results of filtering over the current suggestedUsers from the state
let selectedUsers = assessments.filter((obj) => {
// store immutable retrieval of the client user id in a variable called userId
let userId = obj.getIn(["user", "client_user_id"])
// when the user clicks 'Add' user, if the id of the user matches the selected user id
// the user, represented here by obj, is pushed into the selectedUsers array stored in the state.
if(userId === clientUserId){
return obj.setIn(["user", "selected"], true)
}
// If the user id is not equal to the selected user, that team member is kept in the
// current team array represented by the state.
return userId !== clientUserId
})
// update the state with the current representation of the state determined by the user
// selected team members for assessment requests
this.setState({
suggestedUsers: selectedUsers
})
}
The core of my question is this:
I would like to update the value of the 'selected' key in the users object to false, when this function is invoked.
I'm aware that I can't mutate the List I'm filtering over directly, but I've tried may different approaches to getting the selected value updated (i.e. using updateIn, and setIn). I know I need to set the result of calling setIn to a variable, and return that to the List I'm filtering over, but I can't get the value to update in the existing List. Any help is greatly appreciated. Thanks!
I've verified that this works the way it should when I change the value manually. How can I change it with immutable by updating this one List.
=========================================================================
Thank you to the community for your feedback. Filtering, and mapping did turn out to be overkill. Using immutability-helper, I am able to update the selected value of a particular user at the index that is clicked. One caveat that was not mentioned is using merge to bring your updated data into your previous data. After updating with immutability helper, I push the updated value into an array, then make it a List, and merge it into my original data. Code below:
let users = this.state.teamAssessments
let selectedArray = []
users.map((obj, index) => {
let objId = obj.getIn(["user", "client_user_id"])
if(objId === clientUserId){
const selectedUser = update(this.state.teamAssessments.toJS(), {
[index]: {
user : {
selected: {
$set: true
}
}
}
})
selectedArray.push(selectedUser)
}
})
let updatedArray = fromJS(selectedArray).get(0)
let mergedData = users.merge(updatedArray)
this.setState({
teamAssessments: mergedData
})
You need immutability-helper. Basically, instead of cloning the entire object you just modify small pieces of the object and re-set the state after you are finished.
import update from 'immutability-helper';
const newData = update(myData, {
x: {y: {z: {$set: 7}}},
a: {b: {$push: [9]}}
});
this.setState({varName: newData});
In other words, I would ditch the fromJS and the modifying of the array while enumerating it. First, enumerate the array and create your updates. Then, apply the updates separately. Also, to me the "selected" var seems redundant as you know if they are selected because the name of the array after filtration is "selectedUsers."
If I understand your question correctly, here's what I would suggest:
selectUser(clientUserId) {
let suggestedUsers = this.state.suggestedUsers.map(
userBlock =>
userBlock.setIn(
['user', 'selected'],
userBlock.getIn(['user', 'client_user_id']) === clientUserId
)
);
this.setState({
suggestedUsers,
});
}
To confirm -- you are just trying to modify state.suggestedUsers to have selected be true for the selected user, and false for everyone else? Sounds perfect for Immutable's map function (rather than filter, which will just return the elements of the list for which your predicate function returns something truthy).
BTW, you have an error in your object passed into fromJS -- you need an extra }, after the first assessor_assessment block.