How do I download a file with Angular2

Question

I have a WebApi / MVC app for which I am developing an angular2 client (to replace MVC). I am having some troubles understanding how Angular saves a file.

The request is ok (works fine with MVC, and we can log the data received) but I can't figure out how to save the downloaded data (I am mostly following the same logic as in this post). I am sure it is stupidly simple, but so far I am simply not grasping it.

The code of the component function is below. I've tried different alternatives, the blob way should be the way to go as far as I understood, but there is no function createObjectURL in URL. I can't even find the definition of URL in window, but apparently it exists. If I use the FileSaver.js module I get the same error. So I guess this is something that changed recently or is not yet implemented. How can I trigger the file save in A2?

downloadfile(type: string){

    let thefile = {};
    this.pservice.downloadfile(this.rundata.name, type)
        .subscribe(data => thefile = new Blob([data], { type: "application/octet-stream" }), //console.log(data),
                    error => console.log("Error downloading the file."),
                    () => console.log('Completed file download.'));

    let url = window.URL.createObjectURL(thefile);
    window.open(url);
}

For the sake of completeness, the service that fetches the data is below, but the only thing it does is to issue the request and pass on the data without mapping if it succeeds:

downloadfile(runname: string, type: string){
   return this.authHttp.get( this.files_api + this.title +"/"+ runname + "/?file="+ type)
            .catch(this.logAndPassOn);
}

Answer 1

I share the solution that helped me (any improvement is greatly appreciated)

On your service 'pservice' :

getMyFileFromBackend(typeName: string): Observable<any>{
    let param = new URLSearchParams();
    param.set('type', typeName);
    // setting 'responseType: 2' tells angular that you are loading an arraybuffer
    return this.http.get(http://MYSITE/API/FILEIMPORT, {search: params, responseType: 2})
            .map(res => res.text())
            .catch((error:any) => Observable.throw(error || 'Server error'));
}

Component Part :

downloadfile(type: string){
   this.pservice.getMyFileFromBackend(typename).subscribe(
                    res => this.extractData(res),
                    (error:any) => Observable.throw(error || 'Server error')
                );
}

extractData(res: string){
    // transforme response to blob
    let myBlob: Blob = new Blob([res], {type: 'application/vnd.oasis.opendocument.spreadsheet'}); // replace the type by whatever type is your response

    var fileURL = URL.createObjectURL(myBlob);
    // Cross your fingers at this point and pray whatever you're used to pray
    window.open(fileURL);
}

On the component part, you call the service without subscribing to a response. The subscribe for a complete list of openOffice mime types see : http://www.openoffice.org/framework/documentation/mimetypes/mimetypes.html