Utilizing properties in a fresh function with Angular 2

Question

Utilizing properties in a fresh function with Angular 2

Having an issue with the beacon Minor propriety in a new function. The editor keeps saying that the name cannot be found, and I'm not sure how to resolve it.

Function Example:

listenToBeaconEvents() {
    this.events.subscribe('didRangeBeaconsInRegion', (data) => {

      // update the UI with the beacon list  
      this.zone.run(() => {

        this.beacons = [];
        let beaconList = data.beacons;
        beaconList.forEach((beacon) => {
          let beaconObject = new BeaconModel(beacon);
          this.beacons.push(beaconObject);
          console.log(beacon.minor);
        });
      });
    });
  }

In the above function, console.log(beacon.minor) displays the expected result within the function. However, trying to access it outside of the function doesn't work as intended.

For example:

  isThatBeacon() {
   if (beacon.minor == 12345) {
     console.log('beacon found');
   }
  }

Your help is appreciated.

UPDATE

After implementing Nitzan's solution, the editor error is resolved. However, when testing on the device, I encountered the following error:

inline template:22:4 caused by: Cannot read property 'minor' of undefined

The relevant HTML snippet for reference:

<button class="danger" (click)="isThatBeacon()">is working?</button>

Thank you.

angular typescript ionic2 ibeacon

Answer 1

Answer №1

The variable beacon is scoped only within the function that is passed to beaconList.forEach. Outside of this scope, the variable does not exist.

You have a couple of options based on your needs:

(1) Send an index to isThatBeacon:

isThatBeacon(index: number) {
   if (this.beacons[index].minor == 12345) {
      console.log('beacon found');
   }
}

This option should be used only after all async operations have been completed.

(2) Pass the actual beacon object to isThatBeacon:

isThatBeacon(beacon: BeaconModel) {
   if (beacon.minor == 12345) {
      console.log('beacon found');
   }
}

Answer 2

The variable beacon is scoped only within the function that is passed to beaconList.forEach. Outside of this scope, the variable does not exist.

You have a couple of options based on your needs:

(1) Send an index to isThatBeacon:

isThatBeacon(index: number) {
   if (this.beacons[index].minor == 12345) {
      console.log('beacon found');
   }
}

This option should be used only after all async operations have been completed.

(2) Pass the actual beacon object to isThatBeacon:

isThatBeacon(beacon: BeaconModel) {
   if (beacon.minor == 12345) {
      console.log('beacon found');
   }
}

Answer 3

Answer №2

Here is a slightly different approach to locating a beacon based on your specified value:

isThatBeacon() {
   let beacon = this.beacons.find(x => x.minor === 12345)
   if(beacon != undefined) {
     console.log('beacon found!')
   } else {
     console.log('no beacon found!')
   }
}

If you need to search for a specific beacon based on a dynamic value, simply pass that value to the function and iterate through your array to find it.

The concept behind this solution is to cater to scenarios where the static value may vary, allowing flexibility in searching for any existing beacons. However, if this functionality is not required, Nitzan's answer may be more suitable! :)

isThatBeacon(value) {
   let beacon = this.beacons.find(x => x.minor === value)
   if(beacon != undefined) {
     console.log('beacon found!')
   } else {
     console.log('no beacon found!')
   }
}

If you encounter an error related to data retrieval timing, consider using *ngIf statements or the safe navigation operator when rendering your beacon list:

<div *ngIf="beacons">
  <div *ngFor="let beacon of beacons">{{beacon.minor}}</div>
</div>

You can also utilize the safe navigation operator like this:

<div *ngFor="let beacon of beacons">{{beacon?.minor}}</div>

For more information on the safe navigation operator, check out this resource.

Answer 4

Here is a slightly different approach to locating a beacon based on your specified value:

isThatBeacon() {
   let beacon = this.beacons.find(x => x.minor === 12345)
   if(beacon != undefined) {
     console.log('beacon found!')
   } else {
     console.log('no beacon found!')
   }
}

If you need to search for a specific beacon based on a dynamic value, simply pass that value to the function and iterate through your array to find it.

The concept behind this solution is to cater to scenarios where the static value may vary, allowing flexibility in searching for any existing beacons. However, if this functionality is not required, Nitzan's answer may be more suitable! :)

isThatBeacon(value) {
   let beacon = this.beacons.find(x => x.minor === value)
   if(beacon != undefined) {
     console.log('beacon found!')
   } else {
     console.log('no beacon found!')
   }
}

If you encounter an error related to data retrieval timing, consider using *ngIf statements or the safe navigation operator when rendering your beacon list:

<div *ngIf="beacons">
  <div *ngFor="let beacon of beacons">{{beacon.minor}}</div>
</div>

You can also utilize the safe navigation operator like this:

<div *ngFor="let beacon of beacons">{{beacon?.minor}}</div>

For more information on the safe navigation operator, check out this resource.

Utilizing properties in a fresh function with Angular 2

Answer №1

Answer №2

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