I am building a React app that includes one separate component for CRUD functionality of Products and another separate component for CRUD functionality of Suppliers.
I am using the same saveData method for both components (the Create functionality of CRUD.. that is triggered when the User presses Save after filling in the input fields of Product or Supplier). The saveData method is located in a central ProductsAndSuppliers.js file that is available to both the Products and Supplier components.
In both of the Product & Supplier components, there is a table showing the Products or Suppliers already present as dummy data.
I made a button at the bottom of each page to add a new Product or Supplier... depending on which tab the user has selected on the left side of the screen (Product or Supplier).
Since I am using the same saveData method in both cases, I have the same problem whenever I try to add a new Product or Supplier to each respective table after filling out the input fields. My new Product or Supplier is added.. but twice and I can't figure out why.
I have tried using a spread operator to add the new item to the collection but am having no success:
saveData = (collection, item) => {
if (item.id === "") {
item.id = this.idCounter++;
this.setState((collection) => {
return { ...collection, item }
})
} else {
this.setState(state => state[collection]
= state[collection].map(stored =>
stored.id === item.id ? item : stored))
}
}
Here is my original saveData method that adds the new Product or Supplier, but twice:
saveData = (collection, item) => {
if (item.id === "") {
item.id = this.idCounter++;
this.setState(state => state[collection]
= state[collection].concat(item));
} else {
this.setState(state => state[collection]
= state[collection].map(stored =>
stored.id === item.id ? item : stored))
}
}
my state looks like this:
this.state = {
products: [
{ id: 1, name: "Kayak", category: "Watersports", price: 275 },
{ id: 2, name: "Lifejacket", category: "Watersports", price: 48.95 },
{ id: 3, name: "Soccer Ball", category: "Soccer", price: 19.50 },
],
suppliers: [
{ id: 1, name: "Surf Dudes", city: "San Jose", products: [1, 2] },
{ id: 2, name: "Field Supplies", city: "New York", products: [3] },
]
}
There are issues with both of your implementations.
Starting with the top one:
// don't do this
this.setState((collection) => {
return { ...collection, item }
})
In this case, collection is your component state and you're adding a property called item to it. You're going to get this as a result:
{
products: [],
suppliers: [],
item: item
}
The correct way to do this with the spread operator is to return an object that represents the state update. You can use a computed property name to target the appropriate collection:
this.setState((state) => ({
[collection]: [...state[collection], item]
})
)
* Note that both this and the example below are using the implicit return feature of arrow functions. Note the parens around the object.
In the second code sample you're
mutating the existing state directly which you should not do.
returning an array instead of a state update object.
// don't do this
this.setState(state =>
state[collection] = state[collection].concat(item)
);
Assignment expressions return the assigned value, so this code returns an array instead of an object and I'd frankly be surprised if this worked at all.
The correct implementation is the same as above except it uses concat instead of spread to create the new array:
this.setState(state => ({
[collection]: state[collection].concat(item)
})
);
needlessly fancy, arguably silly id generators:
const nextId = (function idGen (start = 100) {
let current = start;
return () => current++;
})(100);
console.log(nextId()); // 100
console.log(nextId()); // 101
console.log(nextId()); // 102
// ----------------
// a literal generator, just for fun
const ids = (function* IdGenerator(start = 300) {
let id = start;
while (true) {
yield id++;
}
})();
console.log(ids.next().value); // 300
console.log(ids.next().value); // 301
console.log(ids.next().value); // 302
Related
If you have an array as part of your state, and that array contains objects, whats an easy way to update the state with a change to one of those objects?
Example, modified from the tutorial on react:
var CommentBox = React.createClass({
getInitialState: function() {
return {data: [
{ id: 1, author: "john", text: "foo" },
{ id: 2, author: "bob", text: "bar" }
]};
},
handleCommentEdit: function(id, text) {
var existingComment = this.state.data.filter({ function(c) { c.id == id; }).first();
var updatedComments = ??; // not sure how to do this
this.setState({data: updatedComments});
}
}
I quite like doing this with Object.assign rather than the immutability helpers.
handleCommentEdit: function(id, text) {
this.setState({
data: this.state.data.map(el => (el.id === id ? Object.assign({}, el, { text }) : el))
});
}
I just think this is much more succinct than splice and doesn't require knowing an index or explicitly handling the not found case.
If you are feeling all ES2018, you can also do this with spread instead of Object.assign
this.setState({
data: this.state.data.map(el => (el.id === id ? {...el, text} : el))
});
While updating state the key part is to treat it as if it is immutable. Any solution would work fine if you can guarantee it.
Here is my solution using immutability-helper:
jsFiddle:
var update = require('immutability-helper');
handleCommentEdit: function(id, text) {
var data = this.state.data;
var commentIndex = data.findIndex(function(c) {
return c.id == id;
});
var updatedComment = update(data[commentIndex], {text: {$set: text}});
var newData = update(data, {
$splice: [[commentIndex, 1, updatedComment]]
});
this.setState({data: newData});
},
Following questions about state arrays may also help:
Correct modification of state arrays in ReactJS
what is the preferred way to mutate a React state?
I'm trying to explain better how to do this AND what's going on.
First, find the index of the element you're replacing in the state array.
Second, update the element at that index
Third, call setState with the new collection
import update from 'immutability-helper';
// this.state = { employees: [{id: 1, name: 'Obama'}, {id: 2, name: 'Trump'}] }
updateEmployee(employee) {
const index = this.state.employees.findIndex((emp) => emp.id === employee.id);
const updatedEmployees = update(this.state.employees, {$splice: [[index, 1, employee]]}); // array.splice(start, deleteCount, item1)
this.setState({employees: updatedEmployees});
}
Edit: there's a much better way to do this w/o a 3rd party library
const index = this.state.employees.findIndex(emp => emp.id === employee.id);
employees = [...this.state.employees]; // important to create a copy, otherwise you'll modify state outside of setState call
employees[index] = employee;
this.setState({employees});
You can do this with multiple way, I am going to show you that I mostly used. When I am working with arrays in react usually I pass a custom attribute with current index value, in the example below I have passed data-index attribute, data- is html 5 convention.
Ex:
//handleChange method.
handleChange(e){
const {name, value} = e,
index = e.target.getAttribute('data-index'), //custom attribute value
updatedObj = Object.assign({}, this.state.arr[i],{[name]: value});
//update state value.
this.setState({
arr: [
...this.state.arr.slice(0, index),
updatedObj,
...this.state.arr.slice(index + 1)
]
})
}
I'm having two data arrays which are coming from API and sample arrays would be like this
Array 1
[
{userId: 1
description: "Student"
imagePath: "test.png"
status: 1
}]
Array 2
[
{id: 85
accountName: "Rahul"
accountNumber: "11145678"
}
]
In my reactnative app view there's search bar and user should be able to search from these two arrays. So I merged these two arrays into one using
this.searchArray =this.filterArray[0].concat(this.filterArray[1])
So, my searchArray is a single array with Array1 and Array2 data. sample below
[
{userId: 1
description: "Student"
imagePath: "test.png"
status: 1
},
{id: 85
accountName: "Rahul"
accountNumber: "11145678"
}]
My search function is below (I need to search from account number or description)
//Search Filter
searchFilter =searchText=>{
const searchTextData = searchText.toUpperCase();
const userSearch = this.searchArray.filter(item => {
const itemData = `${item.description && item.description.toUpperCase()} ${item. accountName && item.accountName.toUpperCase()}`;
return itemData.indexOf(searchTextData) > -1;
});
}
The search functionality is not working with accountName. It's not getting any results. But if I remove ${item. accountName && item.accountName.toUpperCase()} , then it's working showing data with description. But I need to filter from both
In your array one object can have description or accountNumber so do a check if that exists include it in the itemData variable.
Try doing this
searchFilter =searchText=>{
const searchTextData = searchText.toUpperCase();
const userSearch = this.searchArray.filter(item => {
const itemData = `${item.hasOwnProperty('description'))?item.description.toUpperCase():''} ${item.hasOwnProperty('accountNumber')?item.accountNumber:''}`;
return itemData.indexOf(searchTextData) > -1;
});
}
First merge the two objects into one:
Object.keys(arr2[0]).forEach(key => {
arr1[0][key] = arr2[0][key]
})
Then create the search function:
function searchObject(obj, value){
return Object.keys(obj).some(key => {
return obj[key] === value
})
}
let arr1=[{userId:1,description:"Student",imagePath:"test.png",status:1}],arr2=[{id:85,accountName:"Rahul",accountNumber:"11145678"}];
Object.keys(arr2[0]).forEach(key => {
arr1[0][key] = arr2[0][key]
})
function searchObject(obj, prop, value){
return obj[prop] === value
}
console.log(searchObject(arr1[0], "accountName", "asdf"))
console.log(searchObject(arr1[0], "accountName", "Rahul"))
I have a cart data in this form
const cart = {
'1': {
id: '1',
image: '/rice.jpg',
price: 32,
product: 'Yellow Corn',
quantity: 2,
},
'2': {
id: '2',
image: '/rice.jpg',
price: 400,
product: 'Beans',
quantity: 5,
},
'3': {
id: '3',
image: '/rice.jpg',
price: 32,
product: 'Banana',
quantity: 1,
},
};
In the reducer file I have a function removeItem that is being consumed by the reducer
const removeItem = (items, id) => {
items[id] && delete items[id];
return items;
};
case REMOVE_ITEM: {
const { cart } = state;
const {
payload: { id },
} = action;
return {
...state,
cart: removeItem(cart, id),
};
}
In the component I am using this handleRemove() to handle the deletion
handleRemove = id => {
const {
actions: { removeItem },
} = this.props;
const payload = { id };
removeItem(payload);
};
Now in the redux developer tool, the change is working effectively but the component view is not updating.
Change removeItem function to below code
const removeItem = (items, id) => {
items[id] && delete items[id];
return {...items};
};
This is because component gets change only if reference changes. You can refer this link for more explanation
You need to create a copy of the cart, as otherwise React won't detect the change, because it does reference comparison and you return the same object.
Try to do the removeItem() in this way.
const removeItem = (items, id) => {
let itemsClone = [...items]; // Copies all items into a brand new array
itemsClone [id] && delete itemsClone [id]; // You perform the delete on the clone
return itemsClone ; // you return the clone
};
Do not mutate redux state, redux does not perform a deep diff check in your objects, when you do not mutate and create new objects, it is automatically detected as a different object, because its plain old js objects.
this would be good for further reading : immutable-update-patterns
so your removeItem method should be,
const removeItem = (items, id) => {
let {[id]: remove, ...rest} = items
return rest;
}
You can also use a library to do this, such as dot-prop-immutable , which has set, remove, merge methods to do relevant operations without mutating the object.
I am deleting an one id in an array, how do I setState after filtering it here?
https://codesandbox.io/s/react-example-1m2qn
const Debtors = () => {
const debtors = [
{
id: 1,
name: "John",
relation: "friend",
statement: [
{ id: 1, date: 2010, amount: "1000", purpose: "John" },
{ id: 2, date: 2014, amount: "2000", purpose: "john" }
]
},
,
{
id: 2,
name: "Jack",
relation: "Friend",
statement: [
{ id: 1, date: 2010, amount: "1000", purpose: "jack" },
{ id: 2, date: 2014, amount: "2000", purpose: "jack" }
]
}
];
const [newDebtors, setdebtors] = React.useState(debtors);
const handleDelete = (stat, i) => {
const newList = newDebtors[0].statement.filter(x => x.id !== stat.id);
// How to set debtors here ?
// setdebtors({ ...newDebtors, statement[0]: newList });
console.log(newList)
// How to set debtors here ?
There's two problems:
1) You are iterating off the original debtors object in your render, instead of the newDebtors state you created via useState(), which is why there does not appear to be any UI change.
You need: newDebtors[0].statement.map
2) You need to pass in the item index in your handleDelete() so it knows what item in the array to update. You can have the function do something like this:
In the onClick:
<a
href="javascript:;"
onClick={() => handleDelete(stat, i, 0)}
>
In the handleDelete():
const handleDelete = (stat, i, arrayIndex) => {
const updatedDebtors = newDebtors.map((item, index) => {
if (index === arrayIndex) {
return {
...item,
statement: item.statement.filter(
statement => statement.id !== stat.id
)
};
} else {
return item;
}
});
setDebtors(updatedDebtors);
};
See sandbox for full solution: https://codesandbox.io/s/react-example-x7uoh
You should do it like that:
setdebtors((prevState) => {
let newArray = Array.from(prevState); // Copy the array
// Manipulate the array as you wish
return newArray; // return it
});
The problem is you are mutating the array of "debtors" you need to map through the array of debtors and change any properties in the object.
const handleDelete = (stat, i) => {
const newList = newDebtors.map((debtor, i) => {
if (i === 0) {
debtor.statement = debtor.statement.filter(x => x.id !== stat.id);
}
return debtor;
});
setdebtors(newList);};
An even better approach is to use "useReducer" which is used for mutating more complex pieces of state, like you have here. THe docs are very helpful useReducer
Hmm I dont know what exactly you are trying to do,
Is this what you are looking for?
const handleDelete = (stat, i) => {
const newList = newDebtors[0].statement.filter(x => x.id !== stat.id);
const newFirstItem = {...newDebtors[0],statement: newList}
const newDebtorList = newDebtors.filter(x => x.id !== newFirstItem.id);
newDebtorList.unshift(newFirstItem);
setdebtors(newDebtorList);
}
I know this seems complex but you kinda actually need to do this as you cannot mutate an array in the state...
What I did here is I first created a new statement list(newList), then created a newFirstItem to be set as the new newDebtors[0], then created a new array(newDebtorList) of all the elements of newDebtors except the first one, I modified this array by pushing the newFirstItem to the 0th position(using unshift)
Finally updated the state with this new array...
hope it helps :)
Note: this is for changing the 0th element if you have the id please change the code accordingly
I have a collection of items stored in state:
this.state = {
items: [
{ name: "foo", description: "a foo", index: 0 },
{ name: "bar", description: "a bar", index: 1 },
{ name: "herp", description: "a herp", index: 2 },
{ name: "derp", description: "a derp", index: 3 }
]
};
The index property represents the ordinal position of each item in the collection. At some point I need to re-order these items. For example, "derp" may need to be moved to the front, so the indices of the other items need to be updated:
{ name: "derp", description: "a derp", index: 0 },
{ name: "bar", description: "a bar", index: 1 },
{ name: "herp", description: "a herp", index: 2 },
{ name: "foo", description: "a foo", index: 3 }
I am currently updating the state using update from the immutability-helper package. However, I am certain this is not the correct way to do it (although it works):
// originalIndex is a variable holding the original index
// newIndex is a variable holding the new index
// initialise updatedItems so we can update within the loop
let updatedItems = update(this.state.items, { [originalIndex]: {'index': {$set: newIndex}}});
for (var i = newIndex; i < this.state.items.length; i++) {
if (i !== originalIndex) {
updatedItems = update(updatedItems, { [i]: {'index': {set$: parseInt(this.state.items[i].index) + 1}}});
}
}
This feels like a massive hack.
My question is, is it possible to call update with conditional logic, and so can this loop be replaced with a single call to update?
Assuming that we pull the index property out of each item, you can create the new list like this:
const items = this.state.items.slice();
const value = items[oldIndex];
items.splice(oldIndex, 1); // remove the one you want to move
items.splice(newIndex, 0, value); // add it back to the desired index
this.setState({ items });
That is, use slice to make a (shallow) copy of the list, then use splice to swap the elements around.
Since you're only moving one element at a time, you can save a line using:
const [value] = items.splice(oldIndex, 1);
This assigns the first element of the array returned by splice to value.
If you want to keep index (why?), then you need to reassign the indices:
this.setState({ items: items.map((item, index) => ({ ...item, index })) });
Why not sort the item before hand, on render() :
render(){
let toDisplay = this.state.items.sort( (a,b) => {
if (a.index <= b.index) {
return -1;
}
if (a.index > b.index) {
return 1;
}
return 0;
});
return(
<div className='foo'>
{
toDisplay.map((item, i) => {
return(
<div className="bar" key={i}>{ item.name }</div>
);
})
}
</div>
);
}
Then you can update the state.items only by using :
this.setState({
items: yourUpdatedItems
});