Retrieving an object from an ObservableArray in a Nativescript application

Question

Retrieving an object from an ObservableArray in a Nativescript application

Within my service class, I have an array of quests defined in the following manner:

import { ObservableArray, ChangedData } from 'tns-core-modules/data/observable-array/observable-array';

quests: ObservableArray<Quest>;

To add quests to the array, I use the following code:

let quest = new Quest(data.key, data.value["name"], data.value["description");
this.quests.push(quest);

In a different class, I subscribe to change events of this array:

this.myService.quests.on(ObservableArray.changeEvent,(args:ChangedData<Quest>) => {
    console.log(args.object);
    let quest: Quest = args.object; // can not cast to quest
});

Although I can see my data inside the ChangedData object in the log, I am struggling to cast it back to my object.

Is there a way to accomplish this successfully?

Thank you.

angular typescript nativescript

Answer 1

Answer №1

After some troubleshooting, I came across a helpful solution for your issue here. The problem lies with the typings, as they do not display the required properties. To overcome this, simply assign the type any. Below are the necessary steps to resolve the issue:

this.myService.quests.on(ObservableArray.changeEvent, (args: any) => {
  console.log(args.index);
  //the item which was added
  console.log(this.myService.quests.getItem(args.index));
  //now you can cast it
  let quest = <Quest>this.myService.quests.getItem(args.index);
  console.log(args.action); // Action (In this case "add")
});

Upon testing by adding a dummy object, I came across the following result. Pay attention to the index property for accessing the newly added property.

this.myService.quests.push({ name: 'test1' });
this.myService.quests.push({ name: 'test2' });

Here is the output obtained:

JS: 0 //this is index
JS: {
JS:   "name": "test1"
JS: }
JS: add //this is the action
JS: 1
JS: {
JS:   "name": "test2"
JS: }
JS: add

Answer 2

After some troubleshooting, I came across a helpful solution for your issue here. The problem lies with the typings, as they do not display the required properties. To overcome this, simply assign the type any. Below are the necessary steps to resolve the issue:

this.myService.quests.on(ObservableArray.changeEvent, (args: any) => {
  console.log(args.index);
  //the item which was added
  console.log(this.myService.quests.getItem(args.index));
  //now you can cast it
  let quest = <Quest>this.myService.quests.getItem(args.index);
  console.log(args.action); // Action (In this case "add")
});

Upon testing by adding a dummy object, I came across the following result. Pay attention to the index property for accessing the newly added property.

this.myService.quests.push({ name: 'test1' });
this.myService.quests.push({ name: 'test2' });

Here is the output obtained:

JS: 0 //this is index
JS: {
JS:   "name": "test1"
JS: }
JS: add //this is the action
JS: 1
JS: {
JS:   "name": "test2"
JS: }
JS: add

Retrieving an object from an ObservableArray in a Nativescript application

Answer №1

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