I have a simple app which allows someone to add a numbers into an input, and have those numbers render onto the page (as inputs) which can be edited.
addSiblingValue(evt) {
this.setState({
currentObject: {
...this.state.currentObject,
numberOfSiblings: evt.target.value
}
});
add() {
const array = [...this.state.array, this.state.currentObject];
this.setState({
array
});
}
siblingCountChange(rowIndex, event) {
const array = [...this.state.array];
array[rowIndex].numberOfSiblings = event.target.value;
this.setState({ array });
}
So when I add a number it renders a new input with the value set to the number I've just added, but when I go to change that value, it now is affecting the first input.
The first row of inputs are using their own object currentObject which pushes to to the this.state.array, so I'm not sure why editing anything in that array would affect the currentObject?
Expected behaviour:
User enters a number into the input and clicks add
That input is rendered and can be edited independently
How do I achieve this or what is it I'm doing wrong here?
CodeSandbox
Thank you
When you add this.state.currentObject to the array, it works as an reference, so that the added object in the array and this.state.currentObject are the same object. You can prevent that by adding not the object itself, but a copy of the object into the array:
add() {
const array = [...this.state.array, {"numberOfSiblings": this.state.currentObject.numberOfSiblings}];
this.setState({
array
});
}
siblingCountChange(rowIndex, event) {
const array = [...this.state.array];
array[rowIndex].numberOfSiblings += parseInt(event.target.value);
this.setState({ array });
}
You were not adding the actual number to the current state. I also removed the value from the add like so:
<input
type="text"
onChange={this.siblingCountChange.bind(this, rowIndex)}
/>
You will need to put error handling on the state as a string plus a number leads to NaN error. As you can see the number is parsed before addition.
Thanks to dieckie for pointing me in the right direction. Unfortunately that particular solution did not work, but using Object.assign to create a reference and pushing that to the array did?
Posting here so it helps others/myself in future:
add() {
let copyOfCurrentObject = Object.assign({}, this.state.currentObject);
const array = [...this.state.array, copyOfCurrentObject];
this.setState({
array
})
}
This question was also helpful.
Related
I'm trying to make an add to cart function that first checks if the item being added is already in the cart. If it's in the cart, update its quantity property. If not in the cart, add the entire object to the cart. I think my problem is I'm getting the logic wrong inside my "ADD_ITEM_TO_CART" mutator function.
This is my store with some console.logs() from when I click "addToCart()"
state: {
checkoutCart: [],
},
actions: {
cartAdd({ commit }, payload) {
commit("ADD_ITEM_TO_CART", payload);
},
},
mutations: {
ADD_ITEM_TO_CART(state, payload) {
//CONSOLE.LOG()'s
console.log("state.checkoutCart[0]", state.checkoutCart[0]);
// eslint-disable-next-line
console.log("state.checkoutCart[0].item", state.checkoutCart.item);
console.log("state.checkoutCart", state.checkoutCart);
//IF ITEM ALREADY IN checkoutCart, UPDATE IT'S QUANTITY
if (state.checkoutCart.includes(payload.item)) {
state.checkoutCart.quantity += payload.quantity;
console.log("Item already in cart");
}
//IF ITEM NOT IN checkoutCart, UPDATE THE QUANTITY PROPERTY AND ADD ITEM TO CART
else {
payload.item.quantity = payload.quantity;
state.checkoutCart.push(payload);
}
https://i.imgur.com/rjOOljN.png
I thought this code would work, but it ALWAYS executes the ELSE condition and adds to cart like the
if (state.checkoutCart.includes(payload.item))
isn't being recognized or working at all.
https://i.imgur.com/LLB790Z.png
VueX devtools shows the same thing. An "item" object inside an object inside an array.
I also tried:
ADD_ITEM_TO_CART(state, payload) {
console.log("add_item_to_cart"); <---ONLY PART THAT SHOWS UP IN CONSOLE.LOG() WHEN EXECUTED
//LOOP THROUGH ALL ARRAY ENTRIES TO GAIN ACCESS TO state.checkoutCart.item
for (let i = 0; i < state.checkoutCart.length; i++) {
console.log("i=", i);
console.log("state.checkoutCart.item", state.checkoutCart.item);
//IF ITEM ALREADY IN checkoutCart, UPDATE IT'S QUANTITY
if (state.checkoutCart[i].item.includes(payload.item)) {
state.checkoutCart.quantity += payload.quantity;
console.log("Item already in cart");
return;
};
}
//IF ITEM NOT IN checkoutCart, UPDATE THE QUANTITY PROPERTY AND ADD ITEM TO CART
payload.item.quantity = payload.quantity;
state.checkoutCart.push(payload);
},
because I figured I needed to loop through all the array entries. BUT the for loop doesn't even run, and with this code nothing gets added to the cart at all.
I can't figure out what I'm doing wrong here. Can somebody help? Is my syntax wrong? Or is my logic? Am I accessing the arrays/objects incorrectly? How do I write the "ADD_ITEM_TO_CART" mutator function correctly? I've literally spent all day on this and my brain is shutting down.
EDIT:
https://i.imgur.com/bkU8YSo.png
PAYLOAD
<div v-for="item in items"> <--ACTUALLY PROP FROM PARENT COMPONENT BUT SAME IDEA
<p>
Qty
<select v-model="quantity">
<option value="1">1</option>
<option value="2">2</option>
<option value="3">3</option>
</select>
</p>
<p>
<button type="button" #click="addToCart()">
Add to Cart
</button>
</p>
</div>
let quantity = ref("1");
const addToCart = () => {
console.log("addToCart Running");
store.dispatch("cartAdd", { item: item.value, quantity: quantity.value });
};
That is because your if condition is not checking for what you think.
Array.prototype.includes checks if a value is in the array but there are two cases:
the value is a primary type (string, number, boolean, ...). It compares by value.
the value is an object. Then it compares by reference.
So here, you are checking if the reference of your item object is already included in the array. But it's not, since it's a new object.
Solution: check if there is an object with the same values, not reference.
You can use the some method, and you have to write a condition that checks if two items are equals.
Here is an example if your items have an id:
if (state.checkoutCart.some(item => item.id === payload.item.id))
The problem is indeed inside ADD_ITEM_TO_CART mutation.
As Kapcash has pointed out, two objects having the same properties and the same values are not the same.
In other words, .includes() checks for identity, not equality. To better understand this, consider this example:
const a = { foo: 'bar' }
const b = [{ foo: 'bar' }]
const c = [a]
const d = [{ ...a }]
console.log(b.includes(a)) // false
console.log(c.includes(a)) // true
console.log(d.includes(a)) // false
To get past this, use Kapcash's answer.
I'll just mention the standard way of dealing with this problem is using unique identifiers on objects (e.g: uuids).
Once you fix the above, it's still not going to work, because you'll run into the following problem: inside the if you're attempting to alter state.checkoutCart's quantity. And an array does not have a quantity property.
The proper logic to achieve the desired functionality is (assuming the unique identifier on checkoutCart members is item._id, from the pictures you posted):
ADD_ITEM_TO_CART(state, payload) {
// find the index of a cart element having same `item._id` value as the payload
const index = state.checkoutCart.findIndex(
(el) => el.item._id === payload.item._id
)
if (index > -1) {
// if the index is higher than `-1`, an element was found
// create a copy, update its quantity and then
// replace the original element with the copy
const copy = { ...state.checkoutChart[index] }
copy.quantity += payload.quantity
state.checkoutCart.splice(index, 1, copy)
} else {
// no element found, add payload to `checkoutCart`
state.checkoutCart.push(payload)
}
}
Side note: None of your items should contain a quantity property. That's the cart's responsibility, not the item's. By adding it to the item you end up with two sources of truth which you'd need to keep in sync. You don't want this type of problem.
In a React project, I've certain number of records which also contain input fields like Date and Text components in a Grid. I'm processing the date and text values in save function. All the records are fetched from JSON data, while saving date values its assigned to new key object but new one isn't getting updated with the old one. I have seen many similar posts but, none useful. Please refer to the code below:
Following is the function where I'm extracting both text and date values
const updateGrid = (data) => {
if (Array.isArray(allData) && allData?.length > 0) {
const tempData = allData;
tempData.map(x=> {
if(data.id === x.id) {
x.name = data.textVal
}
// Here I'm assigning the 'Establish' value with 'est'
if(data.id === x.id) {
x['est'] = x['Establish']
x.Establish = data.dateVal
}
})
setDataAll(tempData)
}
console.log('tempdataNew', dataAll)
}
As you can see from above picture, we have two keys, 'est' and 'Establish', but, I need only 'Establish', also getting undefined on 'name' when changed date value and vice-versa. What could be the best optimal solution to tackle this issue?
Please refer to Codesandbox --> https://codesandbox.io/s/jovial-aryabhata-95o2sy?file=/src/Table.js
I'm trying set clickFavIconArray back to an empty array with the hook.
Basically, the setClickFavIconArray has a list of IDs the showFavIcon() checks that ID and if it contains the same ID I want to remove it from the array and update the setClickFavIconArray to the new Array.
However, it just seems to be adding on to the original clickFavIconArray no matter what. Is there a way to clear the clickFavIconArray state back to an [] empty array?
Some help here would be awesome.
const [clickFavIconArray, setClickFavIconArray] = useState([]);
function showFavIcon(id){
if (clickFavIconArray.includes(id)) {
const newArray = clickFavIconArray.filter(item => !id.includes(item))
setClickFavIconArray(newArray)
}
setClickFavIconArray([...clickFavIconArray, id])
}
Simply pass the new value of empty array to setClickFavIconArray():
setClickFavIconArray([])
To make sure that the id is not immediately added to the array again, add a return statement inside the if-statement.
const [clickFavIconArray, setClickFavIconArray] = useState([]);
function showFavIcon(id){
if (clickFavIconArray.includes(id)) {
const newArray = clickFavIconArray.filter(item => !id.includes(item));
setClickFavIconArray(newArray);
return; // make sure that the next line is not executed
}
setClickFavIconArray([...clickFavIconArray, id])
}
There are two issues with the code
filter function seems to be invalid it should be replaced with
clickFavIconArray.filter(item => id != item)
You are adding id again to the array with this
setClickFavIconArray([...clickFavIconArray, id])
If you want to remove id, there is no need for this line in your code.
However you can always set clickFavIconArray to an empty array state using this code:
setClickFavIconArray([])
I have an interface:
export interface ISchoolsPreview {
// Shared
AgeID: string;
School_name?: string;
}
I have a function triggered by a change in a Checkbox:
onChange(code: string, name: string, check: boolean): void {
const tempPreview: ISchoolsPreview = {AgeID: code, School_name: name};
if (check) {
this.schoolsPreview.push(tempPreview);
} else {
//This is where the error lies
const index = this.schoolsPreview.indexOf(tempPreview);
if (index > -1) {
this.schoolsPreview.splice(index, 1);
}
}
}
Check is defined by whether the checkbox was checked or uncheched. If checked it adds a new element of ISchoolsPreview to schoolsPreview. This works and when I step through it shows up and displays correctly on my front end.
However when I uncheck a checkbox, the indexOf(tempPreview) always returns -1 even if I am passing the same entry.
How do I correctly remove an element from my Interface List
You should always find the index of the object based on some property in the object rather than using the whole object itself as follows.
const index = this.schoolsPreview.findIndex((obj) => obj['Property'] === code);
If you thing you will have duplicate codes in the array, then you might have to generate unique ids for each objects and search based on that Id.
Note: I am not sure on this, but passing object to index while return true only if the object references to the same memory. If its a new object you are trying to find, which is in new memory, it might return false. Someone can correct me on this.
I have fixed this by changing:
const index = this.schoolsPreview.indexOf(tempPreview);
to:
const index = this.schoolsPreview.findIndex(s => s.AgeID === code);
See this gist for the complete picture.
Basically I will have this form:
When you click the plus, another row should appear with a drop down for day and a time field.
I can create the code to add inputs to the form, however I'm having trouble with the individual components (selectTimeInput is a row) actually updating their values.
The onChange in the MultipleDayTimeInput is receiving the correct data, it is just the display that isn't updating. I extremely new to react so I don't know what is causing the display to not update....
I think it is because the SelectTimeInput render function isn't being called because the passed in props aren't being updated, but I'm not sure of the correct way to achieve that.
Thinking about it, does the setState need to be called in the onChange of the MultipleDayTimeInput and the input that changed needs to be removed from the this.state.inputs and readded in order to force the render to fire... this seems a little clunky to me...
When you update the display value of the inputs in state, you need to use this.setState to change the state data and cause a re-render with the new data. Using input.key = value is not the correct way.
Using State Correctly
There are three things you should know about
setState().
Do Not Modify State Directly
For example, this will not re-render a
component:
// Wrong
this.state.comment = 'Hello';
Instead, use setState():
// Correct
this.setState({comment: 'Hello'});
The only place where you
can assign this.state is the constructor.
read more from Facebook directly here
I would actually suggest a little bit of a restructure of your code though. It's not really encouraged to have components as part of your state values. I would suggest having your different inputs as data objects in your this.state.inputs, and loop through the data and build each of the displays that way in your render method. Like this:
suppose you have one input in your this.state.inputs (and suppose your inputs is an object for key access):
inputs = {
1: {
selectedTime: 0:00,
selectedValue: 2
}
}
in your render, do something like this:
render() {
let inputs = Object.keys(this.state.inputs).map((key) => {
let input = this.state.inputs[key]
return (<SelectTimeInput
key={key}
name={'option_' + key}
placeholder={this.props.placeholder}
options={this.props.options}
onChange={this.onChange.bind(this, key)}
timeValue={input.selectedTime}
selectValue={input.selectedValue}
/>)
)}
return (
<div>
<button className="button" onClick={this.onAddClick}><i className="fa fa-plus" /></button>
{ inputs }
</div>
);
}
Notice how we're binding the key on the onChange, so that we know which input to update. now, in your onChange function, you just set the correct input's value with setState:
onChange(event, key) {
this.setState({
inputs: Immutable.fromJS(this.state.inputs).setIn([`${key}`, 'selectedTime'], event.target.value).toJS()
// or
inputs: Object.assign(this.state.inputs, Object.assign(this.state.inputs[key], { timeValue: event.target.value }))
})
}
this isn't tested, but basically this Immutable statement is going to make a copy of this.state.inputs and set the selectedTime value inside of the object that matches the key, to the event.target.value. State is updated now, a re-render is triggered, and when you loop through the inputs again in the render, you'll use the new time value as the timeValue to your component.
again, with the Object.assign edit, it isn't tested, but learn more [here]. 2 Basically this statement is merging a new timeValue value in with the this.state.inputs[key] object, and then merging that new object in with the entire this.state.inputs object.
does this make sense?
I modified the onChange in the MultipleDayTimeInput:
onChange(event) {
const comparisonKey = event.target.name.substring(event.target.name.length - 1);
const input = this.getInputState(comparisonKey);
input.selected = event.target.value;
input.display = this.renderTimeInput(input);
let spliceIndex = -1;
for (let i = 0; i < this.state.inputs.length; i++) {
const matches = inputFilter(comparisonKey)(this.state.inputs[i]);
if (matches) {
spliceIndex = i;
break;
}
}
if (spliceIndex < 0) {
throw 'error updating inputs';
}
this.setState({
inputs: [...this.state.inputs].splice(spliceIndex, 1, input)
});
}
The key points are:
// re render the input
input.display = this.renderTimeInput(input);
// set the state by copying the inputs and interchanging the old input with the new input....
this.setState({
inputs: [...this.state.inputs].splice(spliceIndex, 1, input)
});
Having thought about it though, input is an object reference to the input in the this.state.inputs so actually [...this.states.inputs] would have been enough??