The following code fragment in a dao gave an error when casting the response json. The cause is not clear, but 2 code variations were tried:-<\/p>\n
\n\/\/API calls
getFeatures(): Observable<FeaturesSearchResult> {
return this.http.get(this.queryFeatures())<\/pre>\n\/\/ *** This version originally failed citing that property total_rows did not exist
.map(response => {return <FeaturesSearchResult>(response.json())});
}<\/pre>\n<\/blockquote>\nI then tried using the \u201cas\u201d operator for the cast instead of the <> syntax. This worked. Strangely, right at the end I managed to get an example with the\u201d<>\u201d syntax working too, but the reason and differences were not at all clear.
\nHowever, I noted that the latter is also the preferred syntax now, as unlike the \u201c<>\u201d syntax it is also compatible with JSX\/.tsx syntax (JSX is an embeddable React xml-like syntax which transforms into JavaScript)<\/font>
\nSee here<\/a> for details on JSX\/.tsx, and on the React wikipedia entry<\/a>. The working code fragment follows:-<\/p>\n\n\/\/API calls
getFeatures(): Observable<FeaturesSearchResult> {
return this.http.get(this.queryFeatures())\/\/ *** This version originally failed citing that property total_rows did not exist
<\/pre>\n\/\/ *** This version worked by using the \u201cas \u2026\u201d syntax for casting rather than <>
.map(response => {return response.json() as FeaturesSearchResult});
}<\/pre>\n<\/blockquote>\nThe full listing of the code for the working version (less imports for brevity) follows:-<\/p>\n
features-dao.ts<\/u><\/strong><\/pre>\n\n@Injectable()
export class FeaturesDao {
constructor(private appConfig: AppConfig,
private http: Http) {}
\/\/API calls
getFeatures(): Observable<FeaturesSearchResult> {
return this.http.get(this.queryFeatures())
.map(response => {return response.json() as FeaturesSearchResult});
}
\/\/API query definitions
queryFeatures(): string {
return `${this.appConfig.apiBase}_design\/places\/_view\/featuresByOrdinal?include_docs=true`;
}
}
export interface FeaturesSearchResult extends CouchDBResult<FeaturesSearchResultRow> {}
export interface FeaturesSearchResultRow extends CouchDBResultRow<number[], any, FeatureDoc> {}
<\/pre>\n<\/blockquote>\ncouchdb-result.ts<\/u><\/strong><\/pre>\n\nexport interface CouchDBResult<R extends CouchDBResultRow<any,any,any>> {
total_rows: number;
offset: number;
rows: R[];
}
export interface CouchDBResultRow<K,V,D> {
id: string;
key: K;
value: V;
doc?: D;
}
<\/pre>\n<\/blockquote>\nfeature-doc.ts<\/u><\/strong><\/pre>\n\nexport interface FeatureDoc extends CouchDBDoc {
ordinal: number;
name: string;
description: string;
searchable: boolean;
rateable: boolean;
}
<\/pre>\n<\/blockquote>\n","protected":false},"excerpt":{"rendered":"The following code fragment in a dao gave an error when casting the response json. The cause is not clear, but 2 code variations were tried:- \/\/API calls getFeatures(): Observable<FeaturesSearchResult> { return this.http.get(this.queryFeatures()) \/\/ *** This version originally failed citing that property total_rows did not exist .map(response => {return <FeaturesSearchResult>(response.json())}); } I then tried using […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[198,207],"tags":[13,40,16,208],"_links":{"self":[{"href":"https:\/\/salientsoft.co.uk\/index.php?rest_route=\/wp\/v2\/posts\/2012"}],"collection":[{"href":"https:\/\/salientsoft.co.uk\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/salientsoft.co.uk\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/salientsoft.co.uk\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/salientsoft.co.uk\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=2012"}],"version-history":[{"count":6,"href":"https:\/\/salientsoft.co.uk\/index.php?rest_route=\/wp\/v2\/posts\/2012\/revisions"}],"predecessor-version":[{"id":2018,"href":"https:\/\/salientsoft.co.uk\/index.php?rest_route=\/wp\/v2\/posts\/2012\/revisions\/2018"}],"wp:attachment":[{"href":"https:\/\/salientsoft.co.uk\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=2012"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/salientsoft.co.uk\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=2012"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/salientsoft.co.uk\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=2012"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}