asynchronous - How do I properly download and save a list of images? -

i have list of image of urls , download , save each image. unfortunately, keep receiving out of memory exception due exhausted heap space. last attempt saved 2 images , threw "exhausted heap space, trying allocate 33554464 bytes".

my code shown below. logic seems correct believe asynchronous calls may @ fault. there adjustment should make cause downloading sequential? or there method should utilizing?

import 'package:http/http.dart' http; import 'dart:io';  main() {   // loc set of valid urls   // ...    loc.foreach(retrieveimage) }  void retrieveimage(string location) {   uri uri = uri.parse(location);   string name = uri.pathsegments.last;    print("reading $location");   http.readbytes(location).then((image) => saveimage(name, image));  }   void saveimage(string name, var data) {   new file("${name}")     ..writeasbytessync(data);   print(name); } 

if want download them sequentially, can switch future.foreach. enumerators through collection executing function each, waiting future function returns complete before moving on next. it, in turn, returns future completes once final iteration has completed.

instead of

loc.foreach(retrieveimage); 

use

future.foreach(loc, retrieveimage); 

and ensure retrieveimage returns future:

future retrieveimage(string location) {   uri uri = uri.parse(location);   string name = uri.pathsegments.last;    print("reading $location");   return http.readbytes(location).then((image) => saveimage(name, image)); }