Type 'Object' is not assignable to type 'null'-CodePudding

Im getting this "Type 'Object' is not assignable to type 'null'" error ,after i added a function called ngInit which will call the getCountries function in the Service class.

import { Component, OnInit } from '@angular/core';
import {MessageService} from './message.service';

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent {

  title = 'Tour of Heroes';

  countryData = null;
  constructor(private api:MessageService) {}
  ngOnInit() {
    this.api.getCountries().subscribe((data)=>{
      this.countryData = data;
    });
  }

}

CodePudding user response：

Because of your countryData = null property initialization, TypeScript infers the type of countryData to be null. Assigning anything other than null to this property will result in the error you're seeing.

To fix, you can:

Type the property as any:
```
countryData: any = null;
```
Define a type for your data, and set the property to be either that type or null:
```
countryData: CountryDataType | null = null;
```
Define a type for your data, set the property to be of that type, and mark it as optional (note that in this case the initial value is undefined instead of null):
```
countryData?: CountryDataType;
```

CodePudding user response：

You have declare the return type as null or turn off strictNullChecks in your tsconfig.

Change the type null as any.

CodePudding user response：

simple change to make it work is to change the type to any or provide a interface for country

countryData: any;

or as Robby

countryData:CountryDateType