I have 2 fairly simple question.
I have 2 mapped requests sent i close succession to each other, called
by MAIN thread.
First request:
[[RKObjectManager sharedManager] loadObjectsAtResourcePath:#"SomePathToServer"delegate:self]
Second request:
[[RKObjectManager sharedManager] loadObjectsAtResourcePath:#"SomeOTHERpathtoServer" delegate:self];
My question is:
Are they automatically queued by the object manager?
When i run them now the first request will trigger a rather large syncing communication with the webservice. The second request i fired off in the midst of that communication and is not handled/Recieved by RestKit.
If i run my app again, my code detect that the syncing is done, and now the second request is handled - Data is recieved and mapped.
Do i have to manually add my managed requests to a queue?
I havent found anything about it on the net, so if i have to manually
queue it, i wonder if someone has an example or directions to a guide.
I have only found queing examples for simple requests, and i have no
idea on how to put the First and Second request into the queue - if
needed.
Help is much appreciated.
Thomas
RKRequestQueue will do the job. You can add to the queue either RKObjectLoader or RKRequest
Here is the example:
RKRequestQueue *queue =[[RKRequestQueue alloc] init];
queue.delegate = self;
queue.concurrentRequestsLimit = 1;
queue.showsNetworkActivityIndicatorWhenBusy= YES;
[queue addRequest:[[RKObjectManager sharedManager] objectLoaderWithResourcePath:#"resource" delegate:self]];
[queue addRequest:[RKClient sharedClient] requestWithResourcePath:#"Another Resource "delegate: self]];
[queue start];
Related
In a nutshell, I am trying to display data from a publicly available JSON file on the WEB. The process is the following:
I initiate the download with an NSURLSessionDataTask, then I parse and display the JSON or handle errors if they occur. Here is my relevant code:
- (void) initiateDownload {
NSURLSessionConfiguration *sessionConfig = [NSURLSessionConfiguration defaultSessionConfiguration];
sessionConfig.timeoutIntervalForRequest = 5.0f;
sessionConfig.timeoutIntervalForResource = 20.0f;
NSURLSessionDataTask *downloadWeatherTask = [urlSession dataTaskWithRequest:urlRequest
completionHandler:^(NSData *data, NSURLResponse *response, NSError *downloadError) {
if (downloadError) {
dispatch_sync(dispatch_get_main_queue(), ^{
[self errorReceived:downloadError];
});
} else if (data) {
dispatch_sync(dispatch_get_main_queue(), ^{
[self parseWeatherJSON:data];
});
}
}];
[downloadWeatherTask resume];
}
I have a couple of questions about this:
I am not all that familiar with thread handling. Although I added the
dispatch_sync(dispatch_get_main_queue(), ...)
to both completion blocks, and it seems to work, I am not sure this is the best way to be thread safe (before, I received all kinds of error messages and displaying the data took 10 seconds after the download has already finished). Is there a better way to handle the download and the threads or mine is an acceptable solution?
I would like the user to be able to initiate the download process manually any time he/she wants to refresh the data displayed. At first, I initialized the NSURLSessionDataTask once and made it available anywhere within the class; so I could just call resume every time a refresh is called. However, I could not find a command to re-do the download process. Once I called [downloadWeatherTask resume], I was unable to start the task from the beginning.
So, I added the task to a separate function (the one you see above) and initialize it there every time the function is called. This works fine, but I am not sure it is the best way to go. For example, is it memory safe or am I creating a new task every time the user initiates a refresh call and will eventually run out of memory?
Thank you for the answers!
A little more info: I use the latest XCode 11 and target iOS 9 and up.
NSURLSession will, by default, use a dedicated background serial queue for completion blocks (and delegate methods, should you do that). But you really want to make sure you trigger UI updates from the main queue (retrieved via dispatch_get_main_queue()). And you generally want to avoid updating properties and ivars from multiple threads (unless, they have some thread-safety built in to them, which is unusual), so dispatching the updates to those properties/ivars back to the main queue is a nice simple way to achieve thread safety.
So, bottom line, what you’re doing here is fine.
However, I could not find a command to re-do the download process.
You perform (resume) a given task only once. If you want to perform a similar request again, instantiate a new NSURLSessionDataTask.
I am quite new to iOS, trying best way to implement HTTP post / Get communication.
Problem:
I want to make a multiple api calls and each calls will have its separate response. I am trying to write common network utils, Ideally it will take api url, make call and return data to caller. What is the right way to achive it?? I found moderate level of debate and fans for each approach.
Option 1:
dispatch_async(aQueue,^{
...[ make a sync network request get data back]
--- perform operation on data
--- then pass proceed data UI or set it in model.
dispatch_async(dispatch_get_main_queue()
}
Option 2:
-(NSString *) postData:(NSDictionary *)data serverUrl:(NSString *)targetUrl
-- call post data method with seperate delegate for each caller
-- start async request
-- on DidFinishedLaunching or OnError check delegate & then
return response back to callback
Thanks for your inputs.
I think your first option is not good. It is going to block the pooled thread for a long period of time which is not advisable. When implementing Multithreading in any environment pooled threads provided by the system should not be used for long running processes. Second synchronus network call are not really advised and it has its own pitfalls.
Your second option is more viable. An improvement that you may be able to do is to perform the work that happens in the did finish launching to a GCD thread and after the processing send the data on the main thread
There is a wonderful library available, called AFNetworking, which is very easy to implement.
It uses blocks, which greatly simply communication of data between classes (does away with delegates), and is asynchronous.
Example usage is below:
AFHTTPClient *client = [[AFHTTPClient alloc] initWithBaseURL:[NSURL URLWithString:"www.yourwebsite.com/api"]];
NSDictionary *params = #{
#"position": [NSString stringWithFormat:#"%g", position]
};
[client postPath:#"/api" parameters:params success:^(AFHTTPRequestOperation *operation, id responseObject) {
} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
}];
As simple as that! Result is available directly within the class that calls the HTTP Post or Get method.
It even includes image and JSON requests, JSON deserialization, file download with progress callback, and so much more.
I know that conventionally for an app to interact with the internet, it must use a web service to exchange information. However, how would one upload data(photos, text, audio recordings etc.etc.) from app to server(which holds data for all user accounts)? I know some people use an email-to-server tactic from research but even then it sounds ineffective and slow. How do apps such as Instagram upload so fast? I am trying to replicate that sort of uploading. Please guide me in the right direction.
Thanks for the help!
You should definitely look into AFNetworking. Here is an example of my uploading an image to a php web service:
NSData *imageData = UIImagePNGRepresentation(pageImage);
AFHTTPClient *client= [AFHTTPClient clientWithBaseURL:[NSURL URLWithString:#"http://www.SERVER.com"]];
//You can add POST parameteres here
NSDictionary *params = [NSDictionary dictionaryWithObjectsAndKeys:
author, #"author",
title, #"title",
nil];
NSMutableURLRequest *request = [client multipartFormRequestWithMethod:#"POST" path:#"/PATH/TO/WEBSERVICE.php" parameters:params constructingBodyWithBlock: ^(id <AFMultipartFormData>formData) {
//This is the image
[formData appendPartWithFileData: imageData name:#"cover_image" fileName:#"temp.png" mimeType:#"image/png"];
}];
AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc] initWithRequest:request];
//Setup Upload block to return progress of file upload
[operation setUploadProgressBlock:^(NSInteger bytesWritten, long long totalBytesWritten, long long totalBytesExpectedToWrite) {
float progress = totalBytesWritten / (float)totalBytesExpectedToWrite;
NSLog(#"Upload Percentage: %f %%", progress*100);
}];
//Setup Completeion block to return successful or failure
[operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
NSString *response = [operation responseString];
NSLog(#"response: [%#]",response);
//Code to run after webservice returns success response code
} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
NSLog(#"error: %#", [operation error]);
//Code to Run if Failed
}];
[operation start];
Edit- Also I use MBProgressHUD to display to the user the uploading on longer uploads.
As you might know, upload speed is always bound to the speed of the connection type you're using. Even the best upload technique will be slow when the connection is slow (GPRS for example, or EDGE, even 3G can be slow if network coverage is not good).
To upload large sets of data faster/better one thing you could do is compressing the data you're sending using ZIP or any other file compression format you wish or even develop you own compression algorithm (you might not want to do that ;-)).
If you want to reduce the overhead of HTTP/HTTPS connections for example, you can write your very own protocol for data exchange, implement it on the client/server side and upload faster. This will be a lot of work as you have to do all the implementation work not only for the protocol itself as you need to add security etc. But even if you choose to create a protocol, as said in the beginning, it will be slow if the connection is slow.
Update: A presenatation by Mike Krieger (Co-Founder of Instagram) where he covers your question just crossed my way https://speakerdeck.com/u/mikeyk/p/secrets-to-lightning-fast-mobile-design?slide=1.
The reason why you think it's so fast is, that they're updating the UI before the request (the Upload in this case) even completes. This is what Mike describes as "being optimistic". If the request fails you can still notify the user, but in the meantime make him feel productive and act like the request completed successfully.
This is a pretty open ended question but here are a few things to look at:
"Uploading fast" depends on the user's connection and server bandwidth so I won't get into that.
You can upload photos (and other files) by creating NSData objects and attaching them to a POST request. There is already a ton of sample code for uploading NSData but to convert a UIImage you will do the following:
NSData *imageData = UIImagePNGRepresentation(image);
You can do this using the built in Cocoa classes (NSMutableURLRequest) and with 3rd party networking classes (such as AFNetworking - just scroll down to file uploads).
When I send simple data to my webserver, I use the following approach: Use the ASIHttpRequest framework for connecting to your sever. Send the data in HTTP Post body, which is easy to do in the ASIHttpRequest framework. You will want to convert your data to either XML or JSON(use the SBJson framework for this) before sending it. I then write php scripts that parse the json or xml and then input this data into my database with custom SQL scripts. I can give you code snippets if you need them for any of these procedures...
It seems to me that, with your first sentence, you've basically answered your own question.
You need something on your server to receive the files and then you write client code to match. It could be as simple as ftp or as complex as a custom protocol depending on the security and control that you need.
I have the following API call:
URL: /api/some-call
Method: PUT
PARAMS: No params
Its just a simple PUT method. I am trying to use AFNetworking to do that and unfortunately, I am failing. Here's what I have right now:
AFHTTPClient *httpClient = [[AFHTTPClient alloc] initWithBaseURL:url];
NSMutableURLRequest *req = [httpClient requestWithMethod:#"PUT" path:#"" parameters:nil];
AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc] initWithRequest:req];
[operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
NSLog(#"Success");
} failure: ^(AFHTTPRequestOperation *operatn, NSError *error) {
NSLog(#"Failure");
}];
NSOperationQueue *queue = [[NSOperationQueue alloc] init];
[queue addOperation:operation];
This is however, not working. Why is that? Furthermore, what is path supposed to be in a PUT request? I've tried several things and this is what I have now at the end, which I believe should be close to what is correct.
One last question: AFNetworking does not use ARC. Does that mean I still need the autorelease at the end of the NSOperationQueue statement?
EDIT:
Here is error NSLog: Failure Error Domain=com.alamofire.networking.error Code=-1011 "Expected status code in (200-299), got 409" UserInfo=0x7a91fb0 {NSErrorFailingURLKey=*the url*/api/some-call, NSLocalizedDescription=Expected status code in (200-299), got 409}
Well. You are getting a 409 error code.
Quoted from http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html :
10.4.10 409 Conflict
The request could not be completed due to a conflict with the current
state of the resource. This code is only allowed in situations where
it is expected that the user might be able to resolve the conflict and
resubmit the request. The response body SHOULD include enough
information for the user to recognize the source of the conflict.
Ideally, the response entity would include enough information for the
user or user agent to fix the problem; however, that might not be
possible and is not required.
Conflicts are most likely to occur in response to a PUT request. For
example, if versioning were being used and the entity being PUT
included changes to a resource which conflict with those made by an
earlier (third-party) request, the server might use the 409 response
to indicate that it can't complete the request. In this case, the
response entity would likely contain a list of the differences between
the two versions in a format defined by the response Content-Type.
Which means the error is caused by your server not with your code. unless you have provided some wrong parameters.
Well. As for the question regarding the "what is the path supposed to be in PUT".
Normally I'll put baseURL as the domain name of the server.
Which is something like
http://localhost
then i'll put the path to be something like
#"the/rest/of/the/api/url"
then it's easier to switch between development and production servers with just a switch of a baseURL. :)
And for your last question, "AFNetworking does not use ARC. Does that mean I still need the autorelease at the end of the NSOperationQueue statement?"
Does that mean your project is using ARC with AFnetworking, or AFNetworking WITHOUT ARC.
if it's ARC with AFNetworking, you don't have to. Take a look at this
https://github.com/AFNetworking/AFNetworking#arc-support
if it's non-ARC with AFNetworking, you basically have to do all the memory management yourself. :)
Hit me up again if you need more info and i'll edit accordingly. :)
Hope i've helped in someway.
I can only find asynchronous iPad/objective C HTTP examples. How do I do a synchronous web request?
NSURLRequest * urlRequest = [NSURLRequest requestWithURL:aURL];
NSURLResponse * response = nil;
NSError * error = nil;
NSData * data = [NSURLConnection sendSynchronousRequest:urlRequest returningResponse:&response error:&error];
Agree with h4xxr and I would forward you to
http://allseeing-i.com/ASIHTTPRequest/
Which is a fantastic lib that has robust HTTP request methods for both synch and asynch complete with code samples.
Depends on what data you're after. Something simple like this is synchronous, and is handy from time to time:
NSURL *url = [NSURL URLWithString:#"http://someaddress.asp?somedatarequest=1"];
NSArray *dataArray = [NSArray arrayWithContentsOfURL:url];
(Equivalent also exists for Dictionaries)
In this case, the system will wait for a response from someaddress.asp - therefore best perhaps to put something like this into a background thread.
If you have control over the format of the data at the other end, this can be a quick and easy way to get data into an iPhone/iPad app...
Edit - just wanted to state the obvious that typically asynchronous is usually best! No waiting around tying up system resources, especially if remote server has died etc... :)