The function does not yield any result

Question

The function does not yield any result

import { Injectable } from '@angular/core';

export class Test {
  public id: number; public name: string; public fid: number
};

export const TESTS2: Test[] = [
  {id: 1, name: 'Lion', fid: 1},
  {id: 2, name: 'Tiger', fid: 1},
  {id: 3, name: 'Bear', fid: 1},
  {id: 4, name: 'Wolf', fid: 1},
  {id: 5, name: 'Fox', fid: 2},
  {id: 6, name: 'Panda', fid: 2},
  {id: 7, name: 'Kangaroo', fid: 2},
  {id: 8, name: 'Giraffe', fid: 2},
  {id: 9, name: 'Zebra', fid: 3},
  {id: 10, name: 'Horse', fid: 3},
  {id: 11, name: 'Llama', fid: 3},
  {id: 12, name: 'Squirrel', fid: 3}];

let testsPromise2 = Promise.resolve(TESTS2);

@Injectable()
export class TestService2 {
  getTests(id) { 
    let items: Test[] = [];
    for(var i = 0; i < TESTS2.length; i++) {
        if(TESTS2[i].fid == id) { 
        items.push(TESTS2[i]) 
        }
    }
    return testsPromise2;
 }
}

I am encountering an issue where TESTS is not accessible within the getTests function, however, testsPromise can be accessed as I receive all data if I return testsPromise in the getTests function. Why is this happening?

javascript angular typescript

Answer 1

Answer №1

Make sure to start by initializing your items:

  let itemList: Item[] = [];

Answer 2

Make sure to start by initializing your items:

  let itemList: Item[] = [];

Answer 3

Answer №2

Can Test be considered an interface in this scenario?

interface Test {
    id: number;
    name: string;
    fid: number;
}

If that is the case, ensure to initialize the items array before starting the loop (using let):

getTests(id: number) {
    let items: Test[] = [];
    // ...
}

Also, confirm that the declaration of TESTS is accessible within the function:

getTests(id: number) {
    console.log(TESTS); // can you see this output?
    // ...
}

By following the steps above, your code should function correctly.

As a bonus tip, for further optimization, consider rephrasing your function into a single line:

getTests(id: number): Test[] {
    return TESTS.filter((oneTest: Test) => oneTest.fid === id);
}

Answer 4

Can Test be considered an interface in this scenario?

interface Test {
    id: number;
    name: string;
    fid: number;
}

If that is the case, ensure to initialize the items array before starting the loop (using let):

getTests(id: number) {
    let items: Test[] = [];
    // ...
}

Also, confirm that the declaration of TESTS is accessible within the function:

getTests(id: number) {
    console.log(TESTS); // can you see this output?
    // ...
}

By following the steps above, your code should function correctly.

As a bonus tip, for further optimization, consider rephrasing your function into a single line:

getTests(id: number): Test[] {
    return TESTS.filter((oneTest: Test) => oneTest.fid === id);
}

The function does not yield any result

Answer №1

Answer №2

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