How to Pass Data as an Empty Array in Angular 6

Question

How to Pass Data as an Empty Array in Angular 6

After successfully implementing a search function that filters names from an array based on user input, I encountered an issue when trying to make the searchData dynamic by fetching it from a Firebase database:

getArray(): void {
    this.afDatabase.list('/imones')
      .valueChanges()
      .subscribe(res => {
        console.log(res)//should give you the array of percentage.
        this.array = res;
      })
}

this.searchData = this.back.getArray();
  constructor(private completerService: CompleterService, private router: Router, public back: BackService,
             ) {
    this.dataService = completerService.local(this.searchData, 'name', 'name');
}

This resulted in an error being thrown:

https://i.sstatic.net/LnS5P.png

I am seeking guidance on how to resolve this issue. Any help is appreciated.

angular typescript firebase firebase-realtime-database

Answer 1

Answer №1

The issue lies in the constructor where this.SearchData is not recognized as an array. The solution is simple: 1. Ensure your service returns an observable instead of subscribing within the service itself. 2. Move your code from the constructor to ngInit for better initialization. 3. Access the value of searchData within the subscribe function.

It may be challenging to decipher your code, but if your service returns Observables rather than data, your component can be structured as follows:

constructor(private completerService: CompleterService, private router: Router, public back: BackService) {}
ngOnInit() {
  this.back.getArray().subscribe(res => {
    this.searchData = res;
    completerService.local(this.searchData, 'name', 'name').subscribe(res => {
      this.dataService = res;
    });
  })
}

// Alternatively, use switchMap for a cleaner approach
ngOnInit() {
  this.back.getArray().pipe(switchMap(res => {
    this.searchData = res;
    return completerService.local(this.searchData, 'name', 'name');
  })).subscribe(res => {
    this.dataService = res;
  });
}

Answer 2

The issue lies in the constructor where this.SearchData is not recognized as an array. The solution is simple: 1. Ensure your service returns an observable instead of subscribing within the service itself. 2. Move your code from the constructor to ngInit for better initialization. 3. Access the value of searchData within the subscribe function.

It may be challenging to decipher your code, but if your service returns Observables rather than data, your component can be structured as follows:

constructor(private completerService: CompleterService, private router: Router, public back: BackService) {}
ngOnInit() {
  this.back.getArray().subscribe(res => {
    this.searchData = res;
    completerService.local(this.searchData, 'name', 'name').subscribe(res => {
      this.dataService = res;
    });
  })
}

// Alternatively, use switchMap for a cleaner approach
ngOnInit() {
  this.back.getArray().pipe(switchMap(res => {
    this.searchData = res;
    return completerService.local(this.searchData, 'name', 'name');
  })).subscribe(res => {
    this.dataService = res;
  });
}

Answer 3

Answer №2

When utilizing the getArray() method, it does not directly return an array. However, when subscribing to afDatabase.list, you can obtain an array of values. It is important to assign the value to your array within the subscribe callback.

getArray(): void {
this.afDatabase.list('/imones')
  .valueChanges()
  .subscribe(res => {
    console.log(res)//should give you the array of percentage.
    this.searchData = res;
  })}

If values are being received one at a time, you can use the following approach:

getArray(): void {
    this.afDatabase.list('/imones')
      .valueChanges()
      .subscribe(res => {
        console.log(res)//should give you the array of percentage.
        this.searchData.push(res); //searchData must be initialized as empty array
      })
}

Answer 4

When utilizing the getArray() method, it does not directly return an array. However, when subscribing to afDatabase.list, you can obtain an array of values. It is important to assign the value to your array within the subscribe callback.

getArray(): void {
this.afDatabase.list('/imones')
  .valueChanges()
  .subscribe(res => {
    console.log(res)//should give you the array of percentage.
    this.searchData = res;
  })}

If values are being received one at a time, you can use the following approach:

getArray(): void {
    this.afDatabase.list('/imones')
      .valueChanges()
      .subscribe(res => {
        console.log(res)//should give you the array of percentage.
        this.searchData.push(res); //searchData must be initialized as empty array
      })
}

How to Pass Data as an Empty Array in Angular 6

Answer №1

Answer №2

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