Push into Array from Json Angular 5

Question

I'm receiving from an endpoint the following response

{
  "data": [{
    "volume": 4.889999866485596,
    "name": "Carton03",
    "weight": 5.75,
    "storage": 3
  }, {
    "volume": 2.6500000953674316,
    "name": "Carton02",
    "weight": 4.5,
    "storage": 2
  }, {
    "volume": 1.4500000476837158,
    "name": "Carton01",
    "weight": 5,
    "storage": 1
  }],
  "response": "true",
  "type": "Storages"
}

Below I'm trying to create an array at my component:

export class StorageComponent {
   private data: any;
   private stors: Storage [];

   constructor (private storageService: StorageService  ) {}

   storage () {
     this.data =  this.storageService.Storage(); 
     //storageService.Storage is an assistant service that parse the response 
     // and brings me back only the data-array of the response
     for (let i = 0; i < this.data.data.length; i++) {
      const storages = this.data.data[i];
      console.log(storages.storage);
      console.log(storages.name);
      console.log(storages.weight);
      console.log(storages.volume);
      this.stors[i] = storages;
     }   
  }
}

I have a const storages to examine that i can evaluate data and everything is ok.

The problem is that I want to fill up my variable stors that is an array of Storage model which has these attributes , storage,name etc.

I'm trying to do that through the last line but something is wrong , getting :

Cannot set property '0' of undefined

Any ideas?

Sean · Accepted Answer · 2018-05-06 15:42:37Z

3

The error is saying that during the first iteration of the loop, the assignment to this.stors[0] is not possible because it is undefined. The stors property has not been initialized. Consider:

constructor (private storageService: StorageService) {
    this.stors = [];
}

answered May 6, 2018 at 15:42

Sean

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Comments

HDJEMAI · Accepted Answer · 2018-05-06 17:14:41Z

1

Just do an initialization when defining the stors property like this:

private stors: Storage[] = [];

you can initialize other properties as well:

private data: any = null;

you may initialize this in the constructor or ngOnInit, but I think it's a better way like this to initialize arrays directly in the properties.

Initializing your class properties will avoid this type of behavior.

edited May 6, 2018 at 17:14

answered May 6, 2018 at 15:52

HDJEMAI

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