Angular update object in object array

57
votes

Say i have the following object array, lets name it itemArray; 

{
  "totalItems": 2,
  "items": [
    {
      "id": 1,
      "name": "foo"

    },
    {
      "id": 2,
      "name": "bar"
    },
    ]
}

And i have a subscription that returns the updated result of only id 2. How would i update the object array without looping through the entire array?

What i would like is something like the example below;

updateUser(user){
    this.myservice.getUpdate(user.id)
    .subscribe(newitem => {
      this.updateArray(newitem);
    });
}

  updateArray(newitem){
    this.itemArray.items[newitem.id].name = newitem.name
  }

or even better, replacing the entire object;

  updateArray(newitem){
    this.itemArray.items[newitem.id] = newitem
  }

This example however updates the array based on the index of the array. So how do i instead update based on newitem.id?

Template requested in comment:

<tr *ngFor="let u of itemsArray.items; let i = index">
  <td>{{ u.id }}</td>
  <td>{{ u.name }}</td>
  <td>
    <input type="checkbox" checked="u.accepted" [(ngModel)]="itemsArray.items[i].accepted" (ngModelChange)="updateUser(u)">
    <label for="singleCheckbox-{{i}}"></label>
  </td>
</tr>
9
angulartypescript
Are you using this object for rendering the output from a loop on this itemArray (by id of 2)? What I'm getting at, is could you just write a custom pipe for this filter? – JSess
"This example however updates the array based on the index of the array. So how do i instead update based on newitem.id?". Why don't you want to update an item from an index? It will certainly be faster than looping the array searching for a specific id... – developer033
updating from index would be fine. How would i find the right index? Now the index does not correspond with the newitem.id – phicon
although this is a response from the back-end it does not have the index. Could i lookup the index based on the newitem.id in this.itemArray.items? – phicon
Can you include your template in question? – developer033

9 Answers

91
votes

I have created this Plunker based on your example that updates the object equal to newItem.id

Here's the snippet of my functions:

showUpdatedItem(newItem){
    let updateItem = this.itemArray.items.find(this.findIndexToUpdate, newItem.id);

    let index = this.itemArray.items.indexOf(updateItem);


    this.itemArray.items[index] = newItem;

  }

  findIndexToUpdate(newItem) { 
        return newItem.id === this;
  }

Hope this helps.

38
votes

Updating directly the item passed as argument should do the job, but I am maybe missing something here ?

updateItem(item){
  this.itemService.getUpdate(item.id)
  .subscribe(updatedItem => {
    item = updatedItem;
  });
}

EDIT : If you really have no choice but to loop through your entire array to update your item, use findIndex :

let itemIndex = this.items.findIndex(item => item.id == retrievedItem.id);
this.items[itemIndex] = retrievedItem;
28
votes

Another approach could be:

let myList = [{id:'aaa1', name: 'aaa'}, {id:'bbb2', name: 'bbb'}, {id:'ccc3', name: 'ccc'}];
let itemUpdated = {id: 'aaa1', name: 'Another approach'};

myList.find(item => item.id == itemUpdated.id).name = itemUpdated.name;
7
votes

You can try this also to replace existing object

toDoTaskList = [
                {id:'abcd', name:'test'},
                {id:'abcdc', name:'test'},
                {id:'abcdtr', name:'test'}
              ];

newRecordToUpdate = {id:'abcdc', name:'xyz'};
this.toDoTaskList.map((todo, i) => {
         if (todo.id == newRecordToUpdate .id){
            this.toDoTaskList[i] = updatedVal;
          }
        });
3
votes

I would rather create a map

export class item{
    name: string; 
    id: string
}

let caches = new Map<string, item>();

and then you can simply

this.caches[newitem.id] = newitem;

even

this.caches.set(newitem.id, newitem);

array is so 1999. :)

1
votes

Try Array.ForEach() method.

itemArray.ForEach(item =>{
    if(item.id == newitem.id){
        item.name = newitem.name
    }
});
0
votes

You can use for loop to find your element and update it:

updateItem(newItem){
  for (let i = 0; i < this.itemsArray.length; i++) {
      if(this.itemsArray[i].id == newItem.id){
        this.users[i] = newItem;
      }
    }
}
0
votes

In angular/typescript we can avoid mutation of the objects in the array.

An example using your item arr as a BehaviorSubject:

// you can initialize the items$ with the default array
this.items$ = new BehaviorSubject<any>([user1, user2, ...])

updateUser(user){
   this.myservice.getUpdate(user.id).subscribe(newitem => {

     // remove old item
     const items = this.items$.value.filter((item) => item.id !== newitem.id);

     // add a the newItem and broadcast a new table
     this.items$.next([...items, newItem])
   });
}

And in the template you can subscribe on the items$

<tr *ngFor="let u of items$ | async; let i = index">
   <td>{{ u.id }}</td>
   <td>{{ u.name }}</td>
   <td>
        <input type="checkbox" checked="u.accepted" (click)="updateUser(u)">
        <label for="singleCheckbox-{{i}}"></label>
   </td>
</tr>
0
votes
updateValue(data){    
     // retriving index from array
     let indexValue = this.items.indexOf(data);
    // changing specific element in array
     this.items[indexValue].isShow =  !this.items[indexValue].isShow;
}