How to return value of promise using angular 2

Question

This is my promise function i need to return the value of rs.rows.item(0);

     public getCustomer()  : any
  {
        let  db =  window.sqlitePlugin.openDatabase({name: 'data.db', location: 'default'});
        return new Promise((resolve, reject) =>
        {
            db.transaction(function(tx)
            {
                tx.executeSql('SELECT * FROM customer ORDER BY customerId DESC LIMIT 1', [], function(tx, rs)
                {
                     return resolve(rs.rows.item(0));
                }, 
                function(tx, error) 
                {
                    console.log('SELECT error: ' + error.message);
                    reject(error);
                });
            });
        });    
  }

the return value i got an object like this image

i need to get like this example

var customer = getCustomer();
customer.name;
customer.email;

Possible duplicate of [AngularJS $promise then() data undefined](http://stackoverflow.com/questions/25274449/angularjs-promise-then-data-undefined) — Tamas Hegedus, Aug 24 '16 at 13:40
@PAncho may I ask why do you think my answer should not be the accepted answer anymore? :) — sebaferreras, Oct 21 '17 at 15:12

sebaferreras · Answer 1 · 2017-10-21T15:09:30.570

Promises provide us with abstractions that help us deal with the asynchronous nature of our applications. Since we don't know how much time will those operations take (and therefore, when is the data going to be available) you need to use the then() method to execute some code when the data is ready to be used:

this.getCustomer()
    .then((data) => {
        // Here you can use the data because it's ready
        // this.myVariable = data;
    })
    .catch((ex) => {
        console.log(ex);
    });

Volodymyr Khmil · Accepted Answer · 2019-10-17T10:04:13.507

3

first, you need func to get all your data:

getAll(): Promise<Phrase[]> {
    return phrasesPromise;
}

second, if you need one item you can use

ngOnInit() {
    this.phraseService
        .getAll()
        .then((result: Phrase[]) => this.phrases = result);
}

edited Oct 17 '19 at 10:04

answered Oct 20 '17 at 20:27

Volodymyr Khmil

1,078
15
13

score 3 · Answer 3 · answered Oct 10 '18 at 10:40

This is a Promise, so you need to use then:

getCustomer()
    .then(customer => {
        customer.name;
        customer.email;
    });

If you are using TypeScript, or a version of JavaScript that supports async/await, you can do this:

var customer = await getCustomer();
customer.name;
customer.email;

The above will need to be in an async function, like so:

async displayCustomerDetails() {
    var customer = await getCustomer();
    customer.name;
    customer.email;
}

Manuel Domínguez · Answer 4 · 2018-10-10T10:21:58.577

1

You can use the await operator like this:

getCustomer(): Promise<any> {
    [...]
}

async functionThatNeedsCustomer() {
    const customer = await getCustomer();
    const name = customer.email;
    const email = customer.email;
}

The await operator awaits form the Promise to return the result. This can only be done inside an async function (making a function async will make it to return a promise itself).

edited Oct 10 '18 at 10:21

answered Oct 10 '18 at 07:02

Manuel Domínguez

178
2
11

How to return value of promise using angular 2

4 Answers4