iOS downloadFile implementation now async

Downloader.h

@@ -0,0 +1,10 @@
+#import <Foundation/Foundation.h>
+
+typedef void (^ErrorCallback)(NSError*);
+typedef void (^DownloaderCallback)(NSNumber*, NSNumber*, NSNumber*);
+
+@interface Downloader : NSObject <NSURLConnectionDelegate>
+
+- (void)downloadFile:(NSString*)urlStr toFile:(NSString*)downloadPath callback:(DownloaderCallback)callback errorCallback:(ErrorCallback)errorCallback progressCallback:(DownloaderCallback)progressCallback;
+
+@end

Downloader.m

@@ -0,0 +1,83 @@
+#import "Downloader.h"
+
+@interface Downloader()
+
+@property (copy) DownloaderCallback callback;
+@property (copy) ErrorCallback errorCallback;
+@property (copy) DownloaderCallback progressCallback;
+
+@property (retain) NSNumber* statusCode;
+@property (retain) NSNumber* contentLength;
+@property (retain) NSNumber* bytesWritten;
+
+@property (retain) NSFileHandle* fileHandle;
+
+@end
+
+@implementation Downloader
+
+- (void)downloadFile:(NSString*)urlStr toFile:(NSString*)downloadPath callback:(DownloaderCallback)callback errorCallback:(ErrorCallback)errorCallback progressCallback:(DownloaderCallback)progressCallback
+{
+  _callback = callback;
+  _errorCallback = errorCallback;
+  _progressCallback = progressCallback;
+
+  _bytesWritten = 0;
+
+  NSURL* url = [NSURL URLWithString:urlStr];
+
+  NSMutableURLRequest* downloadRequest = [NSMutableURLRequest requestWithURL:url
+                                                                 cachePolicy:NSURLRequestUseProtocolCachePolicy
+                                                             timeoutInterval:30];
+
+  [[NSFileManager defaultManager] createFileAtPath:downloadPath contents:nil attributes:nil];
+
+  _fileHandle = [NSFileHandle fileHandleForWritingAtPath:downloadPath];
+
+  if (!_fileHandle) {
+    NSError* error = [NSError errorWithDomain:@"Downloader" code:NSURLErrorFileDoesNotExist userInfo:@{NSLocalizedDescriptionKey: [NSString stringWithFormat: @"Failed to create target file at path: %@", downloadPath]}];
+
+    return _errorCallback(error);
+  }
+
+  NSURLConnection* connection = [[NSURLConnection alloc] initWithRequest:downloadRequest delegate:self startImmediately:NO];
+
+  [connection scheduleInRunLoop:[NSRunLoop mainRunLoop] forMode:NSDefaultRunLoopMode];
+
+  [connection start];
+}
+
+- (void)connection:(NSURLConnection*)connection didFailWithError:(NSError*)error
+{
+  [_fileHandle closeFile];
+
+  return _errorCallback(error);
+}
+
+- (void)connection:(NSURLConnection*)connection didReceiveResponse:(NSURLResponse*)response
+{
+  NSHTTPURLResponse* httpUrlResponse = (NSHTTPURLResponse*)response;
+
+  _statusCode = [NSNumber numberWithLong:httpUrlResponse.statusCode];
+  _contentLength = [NSNumber numberWithLong: httpUrlResponse.expectedContentLength];
+}
+
+- (void)connection:(NSURLConnection*)connection didReceiveData:(NSData*)data
+{
+  if ([_statusCode isEqualToNumber:[NSNumber numberWithInt:200]]) {
+    [_fileHandle writeData:data];
+
+    _bytesWritten = [NSNumber numberWithUnsignedInteger:[_bytesWritten unsignedIntegerValue] + data.length];
+
+    return _progressCallback(_statusCode, _contentLength, _bytesWritten);
+  }
+}
+
+- (void)connectionDidFinishLoading:(NSURLConnection*)connection
+{
+  [_fileHandle closeFile];
+
+  return _callback(_statusCode, _contentLength, _bytesWritten);
+}
+
+@end

RNFSManager.m

@@ -9,6 +9,7 @@
 #import "RNFSManager.h"
 #import "RCTBridge.h"
 #import "NSArray+Map.h"
+#import "Downloader.h"
 
 @implementation RNFSManager
 
@@ -142,22 +143,22 @@ RCT_EXPORT_METHOD(downloadFile:(NSString *)urlStr
                   filepath:(NSString *)filepath
                   callback:(RCTResponseSenderBlock)callback)
 {
-  NSError *error = nil;
 
-  NSURL *url = [NSURL URLWithString:urlStr];
-  NSData *urlData = [NSData dataWithContentsOfURL:url options:NSDataReadingUncached error:&error];
+  DownloaderCallback downloaderSuccessCallback = ^(NSNumber* statusCode, NSNumber* contentLength, NSNumber* bytesWritten) {
+    return callback(@[[NSNull null], [NSNumber numberWithBool:YES], filepath]);
+  };
 
-  if (error) {
+  ErrorCallback downloaderErrorCallback = ^(NSError* error) {
     return callback([self makeErrorPayload:error]);
-  }
+  };
 
-  BOOL success = [urlData writeToFile:filepath atomically:YES];
+  DownloaderCallback downloaderProgressCallback = ^(NSNumber* statusCode, NSNumber* contentLength, NSNumber* bytesWritten) {
 
-  if (!success) {
-    return callback(@[[NSString stringWithFormat:@"Could not write downloaded data to file at path %@", filepath]]);
-  }
+  };
 
-  callback(@[[NSNull null], [NSNumber numberWithBool:success], filepath]);
+  Downloader* downloader = [Downloader alloc];
+
+  [downloader downloadFile:urlStr toFile:filepath callback:downloaderSuccessCallback errorCallback:downloaderErrorCallback progressCallback:downloaderProgressCallback];
 }
 
 RCT_EXPORT_METHOD(pathForBundle:(NSString *)bundleNamed