How declare return of Promise of array of any objects

Question

I try to define return from the method that would return Promise of an array of objects:

public readAll( ) : Promise<any[]> {

  this.handler.getObject( {
    Bucket              : this.bucket,
    Key                 : this.tableName + '.json',
    ResponseContentType : 'text/plain'
  } )
  .promise( )
  .then( file => { 

    const data : any[] = this._parseData( file.Body.toString( ) ); 

    return new Promise( ( resolve ) => data );
  } )
  .catch( error => {

    return this.writeAll( );
  } );
}

however, I am facing error "[ts] A function whose declared type is neither 'void' nor 'any' must return a value."

What am I doing wrong?

You're not returning a `Promise` from the function `readAll`. put `return this.handler.getObject(...` — Heretic Monkey, Mar 30 '18 at 16:39
Add `return new Promise(_ => _);` at the end of your method, cause not all code return a value. — andnik, Mar 30 '18 at 16:42
Adding return new Promise(_ => _); solve problem - THANK YOU — bensiu, Mar 30 '18 at 16:53
You want `return data` instead of `return new Promise( ( resolve ) => data );`, and also a `return` before your promise chain. — Bergi, Mar 30 '18 at 17:04

Sajeetharan · Accepted Answer · 2018-03-30T17:05:39.100

8

As the error says, your function readAll expects a return of type Promise<any[]> Try returning the Promise inside the readAll

public readAll() : Promise < any[] > {
  return this.handler.getObject({
    Bucket: this.bucket,
    Key: this.tableName + '.json',
    ResponseContentType: 'text/plain'
  })
    .promise()
    .then(file => {
      const data: any[] = this._parseData(file.Body.toString());
      return data;
    })
    .catch(error => {
      return this.writeAll();
    });

}

edited Mar 30 '18 at 17:05

answered Mar 30 '18 at 16:40

Sajeetharan

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I didn't downvote but the answer is not clear enough, and the code is truncated. – Estus Flask Mar 30 '18 at 16:54
i posted a wrong code on edit, this was the initial answer i posted:) sorry for the confusion – Sajeetharan Mar 30 '18 at 17:06
After Bergi antipatern comment - your suggestions are WAY TO GO – bensiu Mar 31 '18 at 19:16

score 1 · Answer 2 · answered Mar 30 '18 at 17:07

1

Suggestion from Andrii Nikolaienko lead to a working solution:

protected readAll( ) : Promise<any[ ]> {

  return new Promise( resolve => {

    this.handler.getObject( {
      Bucket              : this.bucket,
      Key                 : this.tableName + '.json',
      ResponseContentType : 'text/plain'
    } )
    .promise( )
    .then( file => { 

      const data : any[] = this._parseData( file.Body.toString( ) ); 
      resolve( data );
    } )
    .catch( error => {

      resolve( this.writeAll( [ ] ) );
    } )
  } );
}

Thank you for the suggestion.

answered Mar 30 '18 at 17:07

bensiu

24,660
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1

Avoid the [`Promise` constructor antipattern](https://stackoverflow.com/q/23803743/1048572?What-is-the-promise-construction-antipattern-and-how-to-avoid-it)! – Bergi Mar 31 '18 at 10:23
1

Thank you for antipattern warning - after refactoring I go achieved better code what looks exactly like Sajeetharan answer – bensiu Mar 31 '18 at 19:14

How declare return of Promise of array of any objects

2 Answers2