Typescript Error: Type '{}' is not assignable to type 'number'

Question

I have referred other answers but could not solve my problem

console.log(`home.ts : ${result} : ${typeof result},${typeof this.points}`);

returns

home.ts : 50 : number,number

but this line

 this.points = result;

throws the following error:

Typescript Error: Type '{}' is not assignable to type 'number'.

full function

getdefaultscore(){
  this.authService.getdefaultscore().then(
    (result)=>{
      console.log(`home.ts : ${result} : ${typeof result},${typeof this.points}`);
      this.points = result;
    },
    (err)=>{
      this.authService.alertnointernetconnection();
    }
  )
}

this.points is defined as number.

definition of getdefaultscore()

  getdefaultscore(){
    return new Promise((resolve, reject)=>{
        let headers = new Headers();
        headers.append('Content-Type','application/json');
        this.http.post('mysite.com/ionuserpoint.php',JSON.stringify({defaultpoints:true}),headers)
        .subscribe(
            (res) =>{
                let data = res.json();
                data = parseFloat(data);
                alert(`defaults points : ${data}`);
                resolve(data);
            },
            (err) =>{
              reject(err);
            }
        );
    });
  }

I remove http://www before mysite.com because stackoverflow throws some error.

@vSugumar I see the results at runtime. But what is a definition of return type of this.authService.getdefaultscore()? It must be Promise<OfSomething> I believe — Aleksey L.
– Aleksey L., Commented Sep 6, 2017 at 9:10

Titian Cernicova-Dragomir · Accepted Answer · 2017-09-06 19:51:57Z

2

Th problem is in getdefaultscore which returns a Promise<{}> ideally you should change it to return a Promise<number>. Since you do not provide the code for getdefaultscore it is difficult to say what change you should make there. To solve the problem on the caller side you can manually type the result :

declare function getdefaultscore(): Promise<{}>; // Dummy declaration 
var points : number;
function x() {
  getdefaultscore().then((result: number)=>{
    points = result;
  },
  (err)=>{
  })
}

Another version you can consider in Typescript is using async/await to simplify your Promise code:

async function x2() {
  try {
    points = <number>await getdefaultscore()
  } catch (ex) {

  }
}

Edit: You added the getdefaultscore after the original answer. Since you create the promis manually, you just need to type it to Promise<number>.

edited Sep 6, 2017 at 19:51

answered Sep 6, 2017 at 9:14

Titian Cernicova-Dragomir

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3 Comments

Sugumar Venkatesan Over a year ago

I tried parseFloat(resolve) but it throwed a different error

Titian Cernicova-Dragomir Over a year ago

Edited the answer, you just need to type the promise to number

Titian Cernicova-Dragomir Over a year ago

That is assuming the returned json is just a single number, but that is a different problem, if data is a more complex object pareseFloat will fail in other ways

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