``There seems to be an issue with retrieving and displaying data in Ionic2 when using nav

I am facing an issue with displaying the data received from NavParams. I have used console.log() to confirm that I am getting the correct data, but for some reason, I am unable to display it on the new page.

I suspect that there might be an error in how I passed the data, but I am unsure of what mistake I made.

first.ts

import { IonicPage, NavController, NavParams } from 'ionic-angular';
import { LocationsProvider } from '../../providers/locations/locations';

...

    constructor(
        public locations: LocationsProvider,
        public viewCtrl: ViewController,
        public navCtrl: NavController, 
        public actionSheetCtrl: ActionSheetController,
        public http: Http,
        public navParams: NavParams,
    ) { }

    newEntry(param){
        this.navCtrl.push('SecondPage',param);
    }

    openActSheetjob_Type(){
        let actionsheet = this.actionSheetCtrl.create({
            title:"Type",
            buttons:[
                {
                    text: 'Hour',
                    handler: () => {
                        let Hourly = "Hourly";  
                        let results =  this.locations.getData(Hourly);
           
                        console.log(results); // data obtained

                        this.newEntry({ record: results });   //Potential mistake
                    }
                }
            ]
        });
        actionsheetjob_type.present();
    }

Second.html

<ion-list >
    <ion-item *ngFor="let list of this.results">
        <h2>{{ list.Title }}</h2>
        <p>{{ list.Type }}</p>
    </ion-item>
</ion-list>

Second.Ts

ionViewDidLoad(){
    console.log(this.NP.get("record")); //Returns NULL
}

locations.ts

//function to retrieve data
data:any;

getData(jobType){
    if (this.data) {
        return Promise.resolve(this.data);
    }
    return new Promise(resolve => {
        this.http.get('http://localhost/getType.php?Type=' + Type)
        .map(res => res.json())
        .subscribe(data => {
            this.data = data;
            console.log(this.data);
            resolve(this.data);
        });
    });
}

Answer №1

Due to the asynchronous nature of the getData function that returns a Promise, it is imperative to handle the result value appropriately. If you attempt to execute console.log(results) and

this.newEntry({ record: results })
immediately after calling getData, you may not get the expected value. Instead, ensure that you access the value within the then function that executes upon resolving the Promise.

handler: () => {
    let Hourly = "Hourly";  
    this.locations.getData(Hourly)
    .then(results => {
        console.log(results);
        this.newEntry({ record: results });
    }
}

Answer №2

When using

this.navCtrl.push('SecondPage',param);
in your code, make sure you have imported SecondPage in the first.ts file like this:
import { SecondPage } from '../second/second'
. Also, remember to provide the correct class name when calling
this.navCtrl.push(SecondPage,param);

I hope this explanation is helpful!

Answer №3

Here are some code snippets that have been helpful for me, maybe they will assist you as well.

 this.navCtrl.push(SecondPage,{item : xyz});//Used in the First Page

And in the constructor of the second page:

 this.item = params.data.item;// Used in the Second Page

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