I have below interface and model. Now I would like to get an observable after calling API. The code is below:

export class RegistrationListResultModel extends TaskResultModel {
    Users!: UserRegisterModel[];
}

export class UserRegisterModel {
    Id?: number;
    FirstName?: string;
    LastName?: string;
    Email?: string;
    Mobile?: string;
    OrgId?: number;
    Username?: string;
    Password?: string;
    PhotoUrl?: string;
    IsActive?: boolean;
    TimeZoneId?:string;
}

interface SearchResultUserRegistrationInfo {
    userLists: UserRegisterModel[];
    total: number;
}

I have the below function which calls an API and returns result as observable.

private _search(): Observable<SearchResultUserRegistrationInfo> {
        return this.service.get<RegistrationListResultModel>(`${this.apiPATH}lists`).pipe(map(data => {
            const {
                sortColumn,
                sortDirection,
                pageSize,
                page,
                searchFirstName,
                searchLastName,
                searchEmail,
                searchMobile,
                searchUsername
            } = this._state;

            let allMemberLists: UserRegisterModel[] = [];

            if (data) {
                allMemberLists = data.Users;

                // 1. sort              
                let userLists = sort(allMemberLists, sortColumn, sortDirection);

                const total = userLists.length;

                // 3. paginate
                userLists = userLists.slice((page - 1) * pageSize, (page - 1) * pageSize   pageSize);

                return { userLists, total };
            }
            else {
                // In case data is null
                return null
            }
        }));
    }

But I am getting the below errors:

Type 'Observable<{ userLists: UserRegisterModel[]; total: number; } | null>' is not assignable to type 'Observable'. Type '{ userLists: UserRegisterModel[]; total: number; } | null' is not assignable to type 'SearchResultUserRegistrationInfo'. Type 'null' is not assignable to type 'SearchResultUserRegistrationInfo'.ts(2322)

Can anyone help me to solve the errors

CodePudding user response：

Just change the signature of the your _search method:

private _search(): Observable<SearchResultUserRegistrationInfo | null> { ... }