How to download a image from a server url to photo gallery in ios using ionic 3

Hi all,
I just want to download a image from server in app and show that image in photo library in ios. Someone please help
I’m using this code:
const fileTransfer: FileTransferObject = this.transfer.create();‘url’,this.file.documentDirectory + imageName ).then((entry) => {
console.log('download complete: ’ + entry.toURL());
let url=entry.toURL();
// alert(“Download Complete”);
// console.log(‘url is as’,url);
}, (error) => {
alert('error ’ + JSON.stringify(error));