I am trying to login with two text boxes (username and password). I am sending those two variables to web service to check whether there is username and password is available or not. I get the response as message "success" or "failure" from web service with respect to those two values. Then i am fetching that message and with that message i am setting a flag value. But after the session i am not getting that flag value. its showing the default value false.
The problem is i want to login on button action which will call web service using URLSession and data task and i am not able to set the flag. I can do it with NSURL synchronous request but that code is deprecated.
You can view images for the code for login button action function as well as web service function.
login button action
web service function
Thank you in advance.
The way you are using the method webServiceCalledMethod is wrong. The task associated with the URLSession is executed asyncronously. As a result, isLogin variable is returned before your dataTask gets executed.
Instead of returning Bool from asyncronous method, use either closure or delegate pattern to notify of the data task completion state.
Related
I need to perform a scenario with the following steps:
To make a network call with some search parameters provided by the user
Then, to parse its JSON response and create model entities
Then, for each entity created and if it has an associated image URL, to call the corresponding service for downloading such image and to show it in a UICollectionView when download finishes.
I need to handle concurrent network calls when downloading the N images I'd need. User should have the possibility to cancel the current search flow and start a new one. In addition, I should take into account that the cell for a certain image has not been displayed yet or it has been dequeued. So, my question is: which would be the best approach for this?
Perform the first network call (no concurrency) and the JSON response parsing directly using URLSession and URLSessionDownloadTask, and using Operation and OperationQueue for the subsequent steps. Use both invalidateAndCancel() for the URLSession and cancelAllOperations() for the OperationQueue if the user wants to cancel the current search.
Perform the complete process using Operation and OperationQueue.
Any other and more appropriate approach?
The best approach would be to do either a sync or async call to make the first service call. Once completed, parse the json synchronously and then use lazy loading concept (async call) to load if any images are to be downloaded to display the images.
Perform the network call then make the model objects. return these to your VC through your API completion block.
Then reload your collection view and pass the url to each cell and have each cell worry about itself, use something like SDWebImage to show the images async in the cells..
I have an API code, which loads a data necessary for my application.
It's as simple as:
- (void) getDataForKey:(NSString*) key onSuccess:(id (^)())completionBlock
I cache data returned from server, so next calls of that functions should not do network request, until there is some data missing for given key, then I need to load it again from server side.
Everything was okey as long as I had one request per screen, but right now I have a case where I need to do that for every cell on one screen.
Problem is my caching doesn't work because before the response comes in from the first one, 5-6 more are created at the same time.
What could be a solution here to not create multiple network request and make other calls waiting for the first one ?
You can try to make a RequestManager class. Use dictionary to cache the requesting request.
If the next request is the same type as first one, don't make a new request but return the first one. If you choose this solution, you need to manager a completionBlock list then you will be able to send result to all requesters.
If the next request is the same type as first one, waiting in another thread until the first one done. Then make a new request, you API will read cache automatically. Your must make sure your codes are thread-safe.
Or you can use operation queues to do this. Some documents:
Apple: Operation Queues
Soheil Azarpour: How To Use NSOperations and NSOperationQueues
May be there will be so many time consuming solutions for this. I have a trick. Create a BOOL in AppDelegate, its default is FALSE. When you receive first response, then set it TRUE. So when you go to other screen and before making request just check value of your BOOL variable in if condition. If its TRUE means response received so go for it otherwise in else don't do anything.
I am currently creating an MVC application that is currently getting a value from a post from a webhook. I think that the problem is that the application is getting the value from the POST verb but then it is not displaying it because the Get verb is being used to display the View so both Verbs are counter acting each other.
The webhook will fire A Json payload to my application successfully because I have code in it that will send the Json payload in a variable via email to my email account.
Dim body = issue.issue.key
mail.Body = body
That is in a try catch block because in order for it to have a value it must have a value in it and the application will perform the GET first, so there is a null value in the body variable, then it does the POST to get the value but it will not display the value, refreshing will just perform the GET preventing it from being displayed. How can I perform both actions at the same time so I can display a value in a ViewBag for example.
ViewBag.response = status + key
This is the type of structure that I would like to implement to try and fix the error but I do not know how to complete all of the steps:
This is what I have got so far:
The POST is coming in from a webhook and I am reading it like this.
Dim reader As System.IO.StreamReader = New System.IO.StreamReader(HttpContext.Request.InputStream)
Dim rawSendGridJSON As String = reader.ReadToEnd()
Dim tempVar As Rootobject = JsonConvert.DeserializeObject(Of Rootobject)(rawSendGridJSON)
System.Diagnostics.Trace.TraceError(rawSendGridJSON)
I am then trying to store the post values in a table like this:
Public Function CallBack(tempTable as temporaryTable)
Dim tempVar As Rootobject = JsonConvert.DeserializeObject(Of Rootobject)(rawSendGridJSON)
tempVar = temporaryTable.tempVar
I then save the new items in the actual table in the database, then I try to display it in a view on another page. This is not working correctly and the problem lies with this line, as the post is not being correctly read in at the right time. (The value is processing correctly as I can use an email method to send the variables in an email back to the application but this application needs to be real-time efficient code).
Is there a better way to use this method and how can I invoke this process that I want to do properly so that I can display the correct information?
Update
To clarify, there are two posts that are happening, the first one is when the user enters in information and submits it. This is then stored in a database and send to JIRA via email. Once JIRA receives the information, it is sends a HTTP POST webhook JSON Payload back to my application with updated information. I then have deserialized the JSON Payload into a variable called issueKey.
The problem is that on the View page that the information is sent to will automatically display a null value first before the value is sent to it, I want the application to work so that it will actually display/store in a database the values from the Webhook JSON Payload but I cannot figure out how to display the values.
I have now set up a communication channel from SignalR to my MVC application, at the moment it is being received by the MVC and I have set up a SignalR chat Hub in my MVC application, but I don't know how to integrate them, how can this be done?
As I understand it, there are two flows at work here. The user posts data, which triggers an email to Jira. Then sometime later (usually quite fast, but not always) JIRA triggers a webhook in the web application with some updated information, and you want to display this updated information to the user somehow, or at least inform the user when the updated information comes back from JIRA.
I would implement a standard Post-Redirect-Get for the user initiated part (as per br4d's comment). I.e. a post to store the data in the database and send email to jira, which returns a redirect to a get which shows the data stored in the database.
Now for the other part I would use signalr to set up some sort of communications channel to the user. The webook could then send a signal (of sorts) through the communication channel to the users browser and either display the data, or trigger a refresh of the page (if you are updating the database with data from Jira).
It is unclear if you are doing straigt mvc, or some sort of SPA application, but it is not really important. The users browser has no way of knowing about the webhook (which is a part of the webapplication and unrelated to the users session), and you need some sort of communication between the webapplication and the browser, and for this signalr is very very good.
Similar to the iPhone Facebook app search function, I am implementing search as you type functionality into my application although I have a problem when decoding the data into JSON format.
Basically what happens is because some searches take longer than others, they return at different intervals and this causes some small visual issues when the data is presenting on the screen.
I have set an NSLOG after each decode using NSJSONSerialization for the keyword 'industry'
2013-04-09 23:38:18.941 Project Name [42836:1d03] http://fooWebAddress/json/?method=search&limit=10&q=indus
2013-04-09 23:38:19.776 Project Name [42836:3e07] http://fooWebAddress/json/?method=search&limit=10&q=indu
2013-04-09 23:38:20.352 Project Name [42836:8803] http://fooWebAddress/json/?method=search&limit=10&q=indust
2013-04-09 23:38:21.814 Project Name [42836:4e03] http://fooWebAddress/json/?method=search&limit=10&q=industr
2013-04-09 23:38:23.434 Project Name [42836:8803] http://fooWebAddress/json/?method=search&limit=10&q=ind
2013-04-09 23:38:24.070 Project Name [42836:7503] http://fooWebAddress/json/?method=search&limit=10&q=industry
As you can see it is all out of order.
Does anyone have any way of stopping NSJSONSerialization for the previous connection.
Or possibly any other way to go about this problem?
Steps up to NSJSONSerialization...
NSURLRequest (initwithURL)
NSOperationQueue
NSURLConnection (asynchronous)
NSJSONSerialization
Thanks in advance.
When the user starts typing more text, you could cancel your previous connections and ignore any further delegate callbacks you receive from them. Then make the new request for the current text.
You can do this by maintaining some sort of lastRequest or lastOperation reference. When the user starts typing, call [self.lastRequestOrOperation cancel] and ignore any further notifications from that request with a check like if (request != self.lastRequest) { return; } in whatever callbacks you have.
However this has the problem that if the user keeps typing for a while you are constantly cancelling requests and they may not see any results until they have stopped typing.
A better solution would be to add sequencing so that each request is associated with an increasing sequence ID. You then only parse the result and update the UI when the sequence of the response is higher than the last one you received. If you receive any out-of-band responses from earlier, you just ignore them.
This is a much more complex issue than just being able to cancel the NSJSONSerialization. My suggestion is to use NSFetchedResultsController to populate your table view that shows the search results. Use the search term as one of the predicate variable in the NSFetchRequest attached to NSFetchedResultsController. And then, when you parse the results using NSJSONSerialization, store the results with the search term associated with that request. As soon as the search term changed (which you can detect when the user types more characters), re-create the NSFetchedResultsController and reload your table view. In addition, you can also try to cancel the call to parse the previous results if you launched it using performSelector:withObject:afterDelay. Beware that this cannot be always relied upon as the call may have been initiated by the time you are trying to cancel.
Kinda basic, but you could always maintain an nsdictionary of sub-classed NSURLRequests (sub-classed to provide a tag).
Start request - add request to dicationary with tag = array.count - 1, with key matching tag
Connection returns - is the request the most recent request, if so, parse json
Parse JSON - is the request the most recent request, if so, show results, if not, only display if there are no previous results displayed
Request handling - remove key from dictionary
most recent request = does the dictionary contain an object with a higher key value
Currently what you are doing is, you type each character and calling web-service. Why to call web-service for each letter you type. If user is type continuously, then it will increase the load, so call the web-service only when user stops for a particular interval of time. and then pass that string to call web-service or what ever method you are calling.
[NSObject cancelPerformSelectorsWithTarget:self]; // This will cancel your all req which is going to make when user typing without stopping
[self performSelector:#selector(sendSearchRequest) withObject:searchText afterDelay:0.1f]; // This will pass the string to call a web-service method, on which user hold for some time.
Let's say I have an AddProductToCartTask with a method Execute().
Now, the task is being called from a Controller. In the Execute method , there
is a check that if not met - the action is not performed.
Let's say the message returned would be: "You do not have enough bonus to buy
this product".
I thought about launching an event when the domain validation fails - but that would mean that in the Controller I have to have all kinds of class variables that need checking in the action (to determine if I need to set an error message, or i need to redirect .. etc)
Instead of this I could have a method on the task : GetErrorMessages(). If empty
return the JSON object if not empty return the Message. Or the method could return an enum that would tell if i need to redirect or set a message or return the object ....
I'm not sure which road to take. Any input would be appreciated. How do you bubble up messages from your domain layer ?
Edit: this is mainly in an AJAX context. Even though I'm not sure it matters as it's an action that it's getting called from somewhere .
I might be misunderstanding your request, but it seems to me like you want a central messages functionality, rather than something specific to the task object. If you leave it in your task, then the task must be kept in scope and "alive" until the AJAX request.
I do something similar, though directly from the Controller.
I have a static class called Messages. It has AddMessage(), GetLastMessage(), and GetAllMessages() methods. Each one, when first called, will check the user's session variable and, if nothing is found, creates and saves a Queue<string>() object. The methods are basically just an interface to the Queue. The Queue is nice because it handles push/pop which automatically removed "viewed" messages.
My controller does:
Messages.AddMessage("Product Saved");
You could potentially do:
Messages.AddMessage(task...GetErrorMessages());
Then, from my View, I have an html helper that checks how many error messages there are and, if any, creates a <ul> with each message as a <li>.
You could just as easily have a GetMessages() controller that returns any messages as a JSON object.
James