Error occurs when attempting to access property on type 'unknown' without apparent cause

My current project involves an Angular application where I need to fetch data from a Rest API. There's a service that successfully retrieves the data and a component designed to display this data. However, during compilation of my application, I encounter these perplexing errors:

Error: files/files.component.html:43:36 - error TS2339: Property 'platform' does not exist on type 'unknown'.

43                         <td>{{list.platform}}</td>
                                      ~~~~~~~~

  files/files.component.ts:9:16
    9   templateUrl: 'files.component.html'
                     ~~~~~~~~~~~~~~~~~~~~~~
    Error occurs in the template of component FilesComponent.


Error: files/files.component.html:44:36 - error TS2339: Property 'keyword' does not exist on type 'unknown'.

44                         <td>{{list.keyword}}</td>
                                      ~~~~~~~

  files/files.component.ts:9:16
    9   templateUrl: 'files.component.html'
                     ~~~~~~~~~~~~~~~~~~~~~~
    Error occurs in the template of component FilesComponent.

(And so on...)

✖ Failed to compile.

The variable 'list' is unrecognized, and I'm struggling to grasp why. Any guidance or assistance would be greatly appreciated.

This snippet showcases the component code:

(The original component code snippet)
 

Here's the corresponding template:

(The original template code snippet)

And here's the service section:

(The original service code snippet)

I've attempted to define and initialize 'list' in various ways without success:

public list: unknown = [];

declare global list; 

Unfortunately, none of these attempts resolved the issue. I'm stuck at this roadblock and would deeply appreciate any insights or support. Thank you in advance.

Answer №1

It is common to encounter this error message when the list class member does not have a specified type or is unknown. Angular (Typescript) cannot determine the existence of properties such as platform, keyword, etc.

To resolve this issue, create an interface (preferably in a separate file) like the following:

export interface ApiResponse {
   platform: string,
   keyword: string,
   [...other properties]
}

Specify this interface as the type for the list class member:

public list: ApiResponse[] = []

Assign the API response to it within the subscribe method:

this.list = list;

After these steps, you should be able to access these properties in the template.

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