Error when downloading file from server ionic 4

I am trying to download a file from my server but I keep getting errors.





HTML

<ion-button expand="block" (click)="download()">Download Files</ion-button>


TS

download() {
const url = 'http://ccoulter12.lampt.eeecs.qub.ac.uk/api/files/5d248f949c71e.pdf';
const path = this.file.dataDirectory;
const transfer = this.transfer.create();
transfer.download(url, path + 'myfile.pdf').then(entry => {
const url = entry.toURL();

if (this.platform.is('ios')) {
// this.document.viewDocument(url, 'application/pdf', {});
window.open(url);
} else {
this.fileOpener.open(url, 'application/pdf')
.then(() => console.log('File is opened'))
.catch(e => console.log('Error opening file', e));
}
});
}

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