Develop Reference

I'm trying to add to an array of objects that is broken into two inputs in React

So I have an array of objects where the keys are 'cost' and 'service' called estimate. You can add to the array by clicking 'Add' which adds a new index (i) to the array. The issue is on the first cycle I get a good array of {'cost': 2500, 'service': "commercial cleaning"} (imgSet-1) but when I add another item it completely erases the array and sets only one of the nested objects key and value. (imgSet-2). This is the outcome I'm looking for once the state has been saved (imgSet-3) I have tried going with #RubenSmn approach but then I receive this error. (imgSet-4)
imgSet-1 *********
Adding an initial service
Outcome of the initial service addition
imgSet-2 *********
Adding the second service
Outcome of the second service addition
imgSet-3 *********
imgSet-4 *********
Below is the code for the part of the page where you can add services and the output of the text inputs.
const [estimate, setEstimate] = useState([]);
{[...Array(numServices)].map((e, i) => {
return (
<div key={i} className="flex justify-between">
<div>
<NumericTextBoxComponent
format="c2"
name={`cost-${i}`}
value={estimate?.items?.["cost"]?.[i]}
change={(e) =>
setEstimate({ ...estimate, items: [{...estimate?.items?.[i],cost: e?.value}]})
}
placeholder='Price'
floatLabelType="Auto"
data-msg-containerid="errorForCost"
/>
</div>
<div>
<DropDownListComponent
showClearButton
fields={{ value: "id", text: "service" }}
name={`service-${i}`}
value={estimate?.items?.["service"]?.[i]}
change={(e) =>
setEstimate({ ...estimate, items: [{...estimate?.items?.[i],service: e?.value}]})
}
id={`service-${i}`}
floatLabelType="Auto"
data-name={`service-${i}`}
dataSource={estimateData?.services}
placeholder="Service"
data-msg-containerid="errorForLead"
></DropDownListComponent>
<div id="errorForLead" />
</div>
</div>
);
})}
</form>
<button onClick={() => setNumServices(numServices + 1)}>Add</button>
I have tried multiple variations of spread operators but I can't seem to get it to work. My expected result would be:
estimate:{
items: [
{'cost': 2500, 'service': 'Commercial Clean'},
{'cost': 500, 'service': 'Bathroom Clean'},
{'cost': 180, 'service': 'Apartment Clean'},
{etc.}
]
}

The initial state is an array which is not the object you're setting in the change handlers. You can have an initial state like this.
const [estimate, setEstimate] = useState({ items: [] });
You're not adding back the old items of the state when you're setting the new state.
setEstimate({
...estimate,
items: [{ ...estimate?.items?.[i], cost: e?.value }],
// should be something like
// items: [...estimate.items, { ...estimate.items?.[i], cost: e?.value }],
});
But you can't do that since it will create a new object in your items array every time you change a value.
I made this dynamic handleChange function which you can use for you state changes. The first if statement is to check if the itemIndex is already in the items array. If not, create a new item with the propertyName and the value
const handleChange = (e, itemIndex, propertyName) => {
const newValue = e?.value;
setEstimate((prevEstimate) => {
if (prevEstimate.items.length <= itemIndex) {
const newItem = { [propertyName]: newValue };
return {
...prevEstimate,
items: [...prevEstimate.items, newItem]
};
}
// loop over old items
const newItems = [...prevEstimate.items].map((item, idx) => {
// if index' are not the same just return the old item
if (idx !== itemIndex) return item;
// else return the item with the new service
return { ...item, [propertyName]: newValue };
});
return {
...prevEstimate,
items: newItems,
};
});
};
For the Service dropdown, you can do the same for the Cost just change the property name
<DropDownListComponent
...
value={estimate.items[i]?.service}
change={(e) => handleChange(e, i, "service")}
...
></DropDownListComponent>
See here a simplified live version

How can I add new elements to a list?

I was trying to add a new element of array to the list with update of one property (id). I want to make it 1 more than length of array.
But I get some weird outputs, with add every new object. All elements are getting array.length +1 value.
I made several variations of this code with let, const or even operating directly on this.state.produktsToBuy, and every time I got the same output
handleAddToShop = (produktToBuy) => {
const id = this.state.produktsToBuy.length+1;
produktToBuy.id = id + 1;
const produktsToBuy = this.state.produktsToBuy;
produktsToBuy.push(produktToBuy);
this.setState({produktsToBuy});
};
I Should get the output as 1,2,3,4,5,6,7
But on the end I get 7,7,7,7,7,7

Make sure you're not mutating the state directly. In JS, objects are a reference type. When you assign this.state.produktsToBuy to const produktsToBuy and push something to produktsToBuy, you're actually pushing to the original this.state.produktsToBuy and you modify the state.
You can use the spread operator (...) to create a shallow copy of the state (produktsToBuy):
class App extends React.Component {
state = {
items: [
{ name: "test item 1", price: 4.99 },
{ name: "test item 2", price: 7.99 },
{ name: "test item 3", price: 19.99 }
],
produktsToBuy: []
};
handleAddToShop = (produktToBuy) => {
this.setState((prev) => ({
produktsToBuy: [
...prev.produktsToBuy,
{
...produktToBuy,
id: prev.produktsToBuy.length + 1
}
]
}));
};
render() {
return (
<div className="App">
<div style={{ display: "flex" }}>
{this.state.items.map((item) => (
<div
key={item.name}
style={{
border: "1px solid #ccc",
margin: "1rem",
padding: "1rem",
textAlign: "center"
}}
>
<h3>{item.name}</h3>
<p>${item.price}</p>
<button onClick={() => this.handleAddToShop(item)}>Add</button>
</div>
))}
</div>
<pre>{JSON.stringify(this.state.produktsToBuy, null, 2)}</pre>
</div>
);
}
}
ReactDOM.render(<App />, document.getElementById('root'));
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/16.6.3/umd/react.production.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react-dom/16.6.3/umd/react-dom.production.min.js"></script>
<div id="root"></div>

You should be maintaining all of the previous state if there's anything other than just the produktsToBuy. Also, you always need the functional form of setState if anything you're setting is dependent on the previous state(as is OFTEN the case). And, like Zsolt said, you never mutate the state directly in React. Here's my answer (very similar to #Zsolt Meszaros'). Note: .concat creates a new array, so we don't have to worry about mutating the original.
handleAddToShop = (produktToBuy) => {
this.setState((prevState) => {
const { produktsToBuy } = prevState;
return {
...prevState,
produktsToBuy: produktsToBuy.concat([
{
...produktToBuy,
id: produktsToBuy.length + 1,
},
]),
};
});
};

Changing state of object nested in array of objects

As stated in the title I'm trying to change the state of an object nested in an array of objects. I just can not get this to work. I've added a sample of what I'm trying to do in a codesandbox.
I'm using a Material-UI component call ToggleButton (link to demo ToggleButton). I want to change the state to toggle the buttons in the group. I was able to get this working for a create function but can not get it working for my update function.
Trying to change the values of the object in the array is just not working for me. Below are some things I've tried to no success. I want to change the IsTrue: so I can toggle the button to display the users selection.
setAppetizer(true);
setRecipeObjectState({
...recipeObjectState,
Category: [
...recipeObjectState.Category,
{
IsTrue: appetizer,
category: "Appetizer",
},
],
});
This just adds more buttons to my button group.
setAppetizer(true);
setRecipeObjectState((prevState) => ({
...prevState,
Category: [
{
IsTrue: appetizer,
category: "Appetizer",
},
],
}));
I'm just lost now at this point. I just want to also state that this is my first React project that is not just a sandbox for learning the framework and I'm also a jr. developer trying to learn. I have search stackoverflow and nothing has helped me out. I hope I have included enough information for someone to help out.

Your state and app appear to be very convoluted, but the general idea when updating nested array state is to shallowly copy the state at each level where an update is being made. Use array::map to map the Category property to a new array object reference and when the category matches toggle the IsTrue "selected" property.
setRecipeObjectState((prevState) => ({
...prevState,
Category: prevState.Category.map((category) =>
category.category === newCategory // <-- newCategory value from toggled button
? {
...category,
IsTrue: !category.IsTrue
}
: category
)
}));
Since your "selected" calculation is selected={Boolean(item.IsTrue)} you'll want to ensure your IsTrue element values are actually togglable, i.e. just store the boolean value right in the array.
const recipeObject = {
AuthorId: authorId,
BookAuthor: bookAuthor,
BookTitle: bookTitle,
Calories: parseInt(calories),
Category: [
{
IsTrue: false,
category: "Appetizer"
},
{
IsTrue: false,
category: "Breakfast"
},
{
IsTrue: false,
category: "Soup / Salad"
},
{
IsTrue: false,
category: "Vegetarian"
},
{
IsTrue: true,
category: "Meat (Beef, Pork, Chicken)"
},
{
IsTrue: false,
category: "Fish"
},
{
IsTrue: false,
category: "Dessert"
}
],
Description: description,
DurationInMinCook: parseInt(durationInMinCook),
DurationInMinPrep: parseInt(durationInMinPrep),
ImageUrl: imageUrl,
Ingredients: addedIngredients, // array
Instructions: addedInstructions, // array
IsRecipe: true,
Likes: 0,
RecipeId: selectedRecipeId,
ServingSize: parseInt(servingSize),
Title: title,
YouTubeUrl: youTubeUrl
};

You mutating the same reference, you need to render a copy or the component won't render (shallow comparison):
Try updating state like this.
const oldState = recipeObjectState;
oldState.Category = [
{
IsTrue: appetizer,
category: "Appetizer"
}
];
setRecipeObjectState(oldState);

I didn't try your component because it's huge.
Updating a single object property in an array of objects seems to be a very common use-case. Here is generally how you do that. Suppose id is a unique identifier of each object and that we want to toggle selected:
import React, { useState } from "react";
import "./styles.css";
import faker from "faker";
const array = [];
for (let id = 1; id < 10; id++) {
array.push({
id,
name: faker.name.firstName(),
age: faker.random.number(100),
selected: false
});
}
export default function App() {
const [list, setList] = useState(array);
const onClick = (id) => (event) => {
setList((list) =>
list.map((item) =>
item.id === id ? { ...item, selected: !item.selected } : item
)
);
};
return (
<div className="App">
Click on a item:
<ul>
{list.map(({ id, name, age, selected }) => (
<li key={id} onClick={onClick(id)} className="item">
{name} {age}
{selected ? " ✅" : null}
</li>
))}
</ul>
</div>
);
}
https://codesandbox.io/s/xenodochial-river-9sq6g?file=/src/App.js:0-825

Why is may array returning empty?

Hi I am new to react and am trying to use onSelect to return on array of items that are associated with that name. I am using the dot filter method to filter an array so that only items with the same key as the name that is selected appear. However my array returns empty.
class HorizantScroller extends React.Component {
state = {
selected: 'Brands',
statelist: [
{name: "Brands",
items: ["1", "2", "3"]
},
{name: "Films",
items: ["f1", "f2", "f3"]
},
{name: "Holiday Destination",
items: ["f1", "f2", "f3"]
}
]
};
onSelect = key => {
this.setState({ selected: key });
const myList = this.state.statelist;
const myItemDetails = myList.filter(items=>items.key === key);
console.log(myItemDetails)
}
render() {
const { selected } = this.state;
// Create menu from items
const menu = Menu(this.state.statelist, selected);
const {statelist} = this.state;
return (
<div className="HorizantScroller">
<ScrollMenu
data={menu}
arrowLeft={ArrowLeft}
arrowRight={ArrowRight}
selected={selected}
onSelect={this.onSelect}
/>
<Items Items={Items[selected]}/>
</div>
);
}
}
export default HorizantScroller;

According to your data-structure, you need to use use item.name to check for the selectedKey
myList.filter(items=>items.name === key);
Note: you must make sure that you are not updating stateList state after filtering the array, otherwise your your state will loose the data
Instead you must use another state variable to store filtered list or apply the filter while render instead of storing the filtered value in state

I wanted to save two values in this.props.onChange but only is saving the last

I'm using a Table from Ant.Design and has two column with inputs.. I wanted to save the two values from this inputs, but just saving the last one.
My columns:
<Column
title="Wanted"
className="text-center"
render={this.renderInput('Wanted')}
/>
<Column
title="Offered"
className="text-center"
render={this.renderInput('Offered')}
/>
The renderInput function:
renderInput = (id) => (text, record) => (
<Input
name={record.key}
data-id={id}
onChange={e=>this.handleChangeSinglePost(record.key, e.target.value, id)}
/>
);
And the handleChangeSinglePost function:
handleChangeSinglePost(name, value, id){
this.props.onChange(
{
...this.props.value,
[name]: {
id: id,
value: value
}
}
);
}
My console return this:
But i need something like this:
salario-direto:
id: "Wanted"
value: "1"
id: "Offered"
value: "2"
Or save two values, but in this way just saving the last one.

You are overriding the value in
this.props.onChange(
{
...this.props.value,
[name]: {
id: id,
value: value
}
}
);
because both itens have the same name.
When you use [name] you override the last value that had the name salario-direto
If you want something like this
salario-direto:
id: "Wanted"
value: "1"
id: "Offered"
value: "2"
You need to use a Array to store it.
I'm not sure how you need to send the data but i think is something like this ...?
salario-direto: [
{
id: "Wanted"
value: "1"
},
{
id: "Offered"
value: "2"
}
]
IF this is the case you need, on the onChange you need to do this:
this.props.onChange(
{
[name]: this.props.value[name].concat({
id: id,
value: value
})
}
);