After populating the object I want to use the fields to get data for a other object

user_10152435 0
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I have populated my object Contract when using the debugger I can see it has populated the object. But later when I want to use the objects fields but it is undefined. I do not understand why this is the case. Here is the line in question where contract is undefined.

console.log("test id contract client" + this.contract.contractId);

And Here is my full code

import { Component, OnInit } from '@angular/core';
import { ActivatedRoute } from '@angular/router';
import { Client } from '../../models/client';
import { Contract } from '../../models/Contract';
import { ClientService } from '../../services/client.service';
import { ContractService } from '../../services/contract.service';

@Component({
  selector: 'app-contract-customer',
  templateUrl: './contract-customer.component.html',
  styleUrls: ['./contract-customer.component.css']
})
export class ContractCustomerComponent implements OnInit {
  public contractNumber: string;
  public client: Client;
  public contract: Contract;

  constructor(private route: ActivatedRoute, private clientService: ClientService, private contractService: ContractService) { }


  ngOnInit():void  {
    // First get the contract id from the current route.
    const url = window.location.href;
    var parts = url.split('/', 6);

    this.contractNumber = parts[4];

    console.log("Contract Id form url : " + this.contractNumber);

    this.GetContractClient();

  }


  GetContract(id: string) {
    this.contractService.getContract(Number(id)).subscribe(result => {
      this.contract = result;
    }, error => {
      console.log(error)
    });
  }

  GetContractClient() {
    this.GetContract(this.contractNumber);

    console.log("test id contract client" + this.contract.contractId);

    this.clientService.getClient(this.contract.contractId).subscribe(result => {
      this.client = result;
    }, error => {
      console.log('something wrong here!!!')
        console.log(error)
    });
    }
}
angular typescript
1 Answers

In ngOnInit() you call this.GetContractClient()

THEN

In GetContractClient you call this.GetContract(this.contractNumber)

The code in GetContract is asynchronous code. This means that it does not execute immediately. For example, if I said "I'm making a cup of coffee" it does not happen instantly. It takes a while for the kettle to boil. Same with asynchronous code. You haven't provided information about what your service is doing but I am guessing it makes an HTTP call to your server. This takes time. This asynchronous code starts to execute but the rest of the code does not wait for it to finish execution. It continues. Hence, the code:

console.log("test id contract client" + this.contract.contractId);

Executes next.

However, the subscribe block here has not yet been executed. IT ONLY EXECUTES WHEN THE HTTP CALL COMPLETES.

this.contractService.getContract(Number(id)).subscribe(result => {
  // IMPORTANT: THIS LINE ONLY EXECUTES WHEN THE HTTP CALL COMPLETES
  this.contract = result;
}, error => {
  console.log(error)
});

So the code this.contract = result has not yet been executed which is why contract is undefined on this line:

console.log("test id contract client" + this.contract.contractId);

To fix it do this:

this.contractService.getContract(Number(id)).subscribe(result => {
  // IMPORTANT: THIS LINE ONLY EXECUTES WHEN THE HTTP CALL COMPLETES
  this.contract = result;
  console.log("test id contract client" + this.contract.contractId);
}, error => {
  console.log(error)
});

Hope that helps you to understand asynchronous code.

user_12058710
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