I am in the middle of an app re-design and am refactoring and extending my model.
One aspect of my apps model is that the app retrieves data from a web service and populates the model.
My question is: Should my model objects have the capability to implement NSURLSession or should I rely on the VC to provide the connection?
I'm asking from a best practices standpoint. What's the best way to think about this? Should the model be totally on its own or should it have network access?
One consideration is that these model objects are essentially useless without data from the network, meaning data from the Internet is a fundamental aspect of their existence.
If we take SOLID — especially the S for Single Responsible Principle — in account, it becomes obvious, that neither the VC nor the model should do the networking:
a VC's single responsible would be to handle views
the model's purpose would be to hold data
networking should be done by a third class, a networking controller.
This three points will fulfill SOLID, but how do you get data from the network into model objects show on a view?
Well, this depends on your overall architectural design on the app, but a common approach would be to use callback — either a delegate protocol or a block — with your network controller.
You create a network controller in the app delegate and pass it from view controller to view controller via properties to any place in the app were newly fetched data is needed. I wouldn't use a singleton here, as that violates O, I & D of SOLID.
Add a class method to your model +(NSArray *)modelObjectsFromDictionaries:(NSArray *) or similar.
In the view controller you can now do
-(void)viewDidLoad
{
[super viewDidLoad];
__weak typeof(self) weakSelf = self;
[self.networkController fetchModels:^(NSArray *modelDictionaries, NSError *error){
typeof(weakSelf) self = weakSelf;
if(self) {
if(!error){
[self.dataSource addOrUpdateData:[Model modelObjectsFromDictionaries:modelDictionaries]];
} else {
// error handling
}
}
}];
}
This is just a starting point. For more complicated APIs it might be useful to use an api controller that itself uses the networking controller and maybe a persistence controller.
Although instead of a Model class method you might want to use some sort of mapping and abstract factory pattern… But all this things would require more information about your app and are out of the scope for this question.
Update:
I created a sample project to demonstrate this.
It is slightly different than what I say above:
As it uses a table view, I am using a data source class to populate it. Instead of the view controller the data source will tell the network controller to fetch new data.
I am using OFAPopulator for this, a library written by me to populate table views and collection views in a SOLID-conform fashion, or to «Keep view controllers clean and MVC smart».
#import "AppDelegate.h"
#import "VSNetworkController.h"
#implementation AppDelegate
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
[self.window.rootViewController setValue:[[VSNetworkController alloc] initWithBaseURL:[NSURL URLWithString:#"http://api.goeuro.com/api/v2/"]]
forKey:#"networkController"];
return YES;
}
#end
// VSNetworkController.h
#import <Foundation/Foundation.h>
#interface VSNetworkController : NSObject
-(instancetype)initWithBaseURL:(NSURL *) baseURL;
-(void)suggestionsForString:(NSString *)suggestionString
responseHandler:(void(^)(id responseObj, NSError *error))responseHandler;
#end
// VSNetworkController.m
#import "VSNetworkController.h"
#interface VSNetworkController ()
#property (nonatomic, strong) NSURL *baseURL;
#end
#implementation VSNetworkController
-(instancetype)initWithBaseURL:(NSURL *)baseURL
{
self = [super init];
if (self) {
_baseURL = baseURL;
}
return self;
}
-(void)suggestionsForString:(NSString *)suggestionString
responseHandler:(void(^)(id responseObj, NSError *error))responseHandler
{
NSURL *url = [self.baseURL URLByAppendingPathComponent:[NSString stringWithFormat:#"position/suggest/en/%#", suggestionString]];
NSURLRequest *request = [NSURLRequest requestWithURL:url];
[NSURLConnection sendAsynchronousRequest:request
queue:[NSOperationQueue mainQueue]
completionHandler:^(NSURLResponse *response,
NSData *data,
NSError *connectionError) {
responseHandler([NSJSONSerialization JSONObjectWithData:data options:0 error:nil], connectionError);
}];
}
#end
// VSLocationSuggestion.h
#import <Foundation/Foundation.h>
#import CoreLocation;
#interface VSLocationSuggestion : NSObject
#property (nonatomic, copy, readonly) NSString *name;
#property (nonatomic, copy, readonly) NSString *country;
#property (nonatomic, strong, readonly) CLLocation *position;
+(NSArray *)suggestionsFromDictionaries:(NSArray *)dictionaries;
#end
// VSLocationSuggestion.m
#import "VSLocationSuggestion.h"
#interface VSLocationSuggestion ()
#property (nonatomic, copy) NSString *name;
#property (nonatomic, copy) NSString *country;
#property (nonatomic, strong) CLLocation *position;
#end
#implementation VSLocationSuggestion
+(NSArray *)suggestionsFromDictionaries:(NSArray *)dictionaries
{
NSMutableArray *array = [#[] mutableCopy];
[dictionaries enumerateObjectsUsingBlock:^(NSDictionary *suggestionDict, NSUInteger idx, BOOL *stop) {
[array addObject:[[self alloc] initWithDictionary:suggestionDict]];
}];
return [array copy];
}
-(instancetype)initWithDictionary:(NSDictionary *)dict
{
self = [super init];
if (self) {
_name = dict[#"name"];
_country = dict[#"country"];
CLLocationDegrees latitude = [dict[#"geo_position"][#"latitude"] doubleValue];
CLLocationDegrees longitude =[dict[#"geo_position"][#"longitude"] doubleValue];
_position = [[CLLocation alloc] initWithLatitude:latitude longitude:longitude];
}
return self;
}
#end
// VSSuggestionDataSource.h
#import <Foundation/Foundation.h>
#import <OFADataProvider.h>
#class VSNetworkController;
#interface VSSuggestionDataSource : NSObject <OFADataProvider>
-(instancetype)initWithNetworkController:(VSNetworkController *)networkController;
-(void)setNewSuggestions:(NSArray *)suggetsions;
-(void)enteredStringForSuggestions:(NSString *)suggestionString;
#end
// VSSuggestionDataSource.m
#import "VSSuggestionDataSource.h"
#import "VSNetworkController.h"
#import "VSLocationSuggestion.h"
#interface VSSuggestionDataSource ()
#property (nonatomic, copy) void (^available)(void);
#property (nonatomic, strong) VSNetworkController *networkController;
#end
#implementation VSSuggestionDataSource
#synthesize sectionObjects;
-(instancetype)initWithNetworkController:(VSNetworkController *)networkController
{
self = [super init];
if (self) {
_networkController = networkController;
}
return self;
}
-(void)dataAvailable:(void (^)(void))available
{
_available = available;
}
-(void)setNewSuggestions:(NSArray *)suggetsions
{
self.sectionObjects = suggetsions;
self.available();
}
-(void)enteredStringForSuggestions:(NSString *)s
{
__weak typeof(self) weakSelf = self;
[self.networkController suggestionsForString:s responseHandler:^(NSArray *responseObj, NSError *error) {
typeof(weakSelf) self = weakSelf;
if (self) {
if (!error && responseObj) {
NSArray *suggestion = [VSLocationSuggestion suggestionsFromDictionaries:responseObj];
[self setNewSuggestions:suggestion];
}
}
}];
}
#end
// ViewController.h
#import <UIKit/UIKit.h>
#class VSNetworkController;
#interface ViewController : UIViewController
#property (nonatomic, strong) VSNetworkController *networkController;
#end
// ViewController.m
#import "ViewController.h"
#import "VSLocationSuggestion.h"
#import <OFAViewPopulator.h>
#import <OFASectionPopulator.h>
#import "VSSuggestionDataSource.h"
#interface ViewController ()
#property (weak, nonatomic) IBOutlet UITableView *tableView;
#property (strong, nonatomic) OFAViewPopulator *viewPopultor;
#property (strong, nonatomic) VSSuggestionDataSource *dataSource;
- (IBAction)textChanged:(UITextField *)sender;
#end
#implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
self.dataSource = [[VSSuggestionDataSource alloc] initWithNetworkController:self.networkController];
OFASectionPopulator *sectionPopulator = [[OFASectionPopulator alloc] initWithParentView:self.tableView
dataProvider:self.dataSource
cellIdentifier:^NSString *(id obj, NSIndexPath *indexPath) {
return #"Cell";
} cellConfigurator:^(VSLocationSuggestion *obj, UITableViewCell *cell, NSIndexPath *indexPath) {
cell.textLabel.text = obj.name;
}];
sectionPopulator.objectOnCellSelected = ^(VSLocationSuggestion *suggestion, UIView *cell, NSIndexPath *indexPath ){
NSString * string =[NSString stringWithFormat:#"%#, %# (%f %f)", suggestion.name, suggestion.country, suggestion.position.coordinate.latitude, suggestion.position.coordinate.longitude];
UIAlertController *avc = [UIAlertController alertControllerWithTitle:#"Selected" message:string preferredStyle:UIAlertControllerStyleAlert];
UIAlertAction *cancelAction = [UIAlertAction
actionWithTitle:NSLocalizedString(#"Cancel", #"Cancel action")
style:UIAlertActionStyleCancel
handler:^(UIAlertAction *action)
{
;
}];
[avc addAction:cancelAction];
[self presentViewController:avc animated:YES completion:NULL];
};
self.viewPopultor = [[OFAViewPopulator alloc] initWithSectionPopulators:#[sectionPopulator]];
}
- (IBAction)textChanged:(UITextField *)sender
{
NSString *s = sender.text;
if ([s length]) {
[self.dataSource enteredStringForSuggestions:s];
}
}
#end;
I made this code available on github: https://github.com/vikingosegundo/LocationSugesstion
Related
I'm trying to use Firebase to save a small amount of user data in an app I'm working on. I'd like to save the users zip code (which they'll enter) and then let them choose to follow certain topics.
I currently have the zip code being saved, but I can't get the child data to save correctly.
Can anyone help point out what I need to add next to allow child data to be saved off of a users zip code?
#import "ZipCodeVC.h"
#import <FirebaseStorage/FirebaseStorage.h>
#import <FirebaseDatabase/FirebaseDatabase.h>
#interface ZipCodeVC ()
#property FIRDatabaseReference *ref;
#end
#implementation ZipCodeVC
- (void)viewDidLoad {
[super viewDidLoad];
self.ref=[[FIRDatabase database]reference];
[[self.ref child:#"Zip Code"] setValue:#"61354"];
}
#end
Figured it out!
#import "ZipCodeVC.h"
#import <FirebaseStorage/FirebaseStorage.h>
#import <FirebaseDatabase/FirebaseDatabase.h>
#import Firebase;
#interface ZipCodeVC ()
#property NSString *uid;
#property (strong, nonatomic) IBOutlet UITextField *zipcodeTextField;
#property FIRDatabaseReference *ref;
#end
#implementation ZipCodeVC
- (void)viewDidLoad {
[super viewDidLoad];
}
- (IBAction)tappedSubmit:(id)sender
{
[[FIRAuth auth]
signInAnonymouslyWithCompletion:^(FIRUser *_Nullable user, NSError *_Nullable error) {
if (!error) {
self.uid = user.uid;
self.ref=[[FIRDatabase database]reference];
//[[self.ref child:#"User ID"] setValue:uid]; old code that worked for creating main value
[self writeNewPost:self.uid zipcode:self.zipcodeTextField.text title:#"Test Title" body:#"Body"];
}
}];
}
- (void)writeNewPost:(NSString *)userID zipcode:(NSString *)zipcode title:(NSString *)title body:(NSString *)body
{
NSString *key = self.uid;
NSDictionary *post = #{#"uid": userID,
#"zip code": zipcode,
#"title": title,
#"body": body};
NSDictionary *childUpdates = #{[NSString stringWithFormat:#"/user/%#", key]: post};
[_ref updateChildValues:childUpdates];
}
#end
I'm pretty new to objective-c and need some tips for my challenge.
I have 2 view controllers and need to show xml data retrieved from FirstViewController to the TermsViewController.
I'm successful getting user input and retrieve xml objects I need.
But don't know how to show the user name in the TermsViewController.m
Since data is downloaded async, can't figure out how to implement this for IOS 6.
Thanks in advance.
FirstViewController.h
#import <UIKit/UIKit.h>
#interface FirstViewController : UIViewController
#property (weak, nonatomic) IBOutlet UIButton *accessButton;
#property (weak, nonatomic) IBOutlet UITextField *codeField;
#property (weak, nonatomic) NSString *codeUser;
#property (strong, nonatomic) NSString *nameUser;
#property (strong, nonatomic) NSDictionary *xmlDictionary;
#end
TermsViewController.h
#import <UIKit/UIKit.h>
#interface TermsViewController : UIViewController
#property (weak, nonatomic) IBOutlet UILabel *nameLabel;
#property (strong, nonatomic) NSString *nameUserTerms;
#end
FirstViewController.m
#import "FirstViewController.h"
#import "TermsViewController.h"
#import "XMLReader.h"
#interface FirstViewController ()
#property (nonatomic, strong) NSMutableURLRequest *postRequest;
#property NSUInteger responseStatusCode;
#property (nonatomic, strong) NSString *theXML;
#end
#implementation FirstViewController
- (void)viewDidLoad {
[super viewDidLoad];
}
- (IBAction)accessButton:(UIButton *)sender {
self.codeUser = self.codeField.text;
NSString *xmlCode = [NSString stringWithFormat:
#"<?xml version='1.0' encoding='utf-8'?>\n"
"<soap:Envelope xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance' xmlns:xsd='http://www.w3.org/2001/XMLSchema' xmlns:soap='http://schemas.xmlsoap.org/soap/envelope/'>"
"<soap:Body>\n"
"<GetInterview xmlns='http://www.url.com/url.JCV'>\n"
"<Codigo>"
"%#"
"</Codigo>\n"
"</GetInterview>\n"
"</soap:Body>\n"
"</soap:Envelope>", self.codeUser];
NSLog(#"User code is: %#", self.codeUser);
NSLog(#"XML is: %#", xmlCode);
self.postRequest = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:#"http://www.url.com/url.JCV/web.url.asmx"]];
[self.postRequest setValue:#"text/xml" forHTTPHeaderField:#"Content-Type"];
[self.postRequest setHTTPMethod:#"POST"];
[self.postRequest setHTTPBody:[NSMutableData dataWithBytes:[xmlCode UTF8String] length:strlen([xmlCode UTF8String])]];
NSURLConnection *conn = [[NSURLConnection alloc] initWithRequest:self.postRequest delegate:self];
if (conn) {
NSLog(#"Connected to: %#", conn);
} else {
NSLog(#"Connection Error");
}
[self.codeField resignFirstResponder];
}
FirstViewController.m connectionDidFinishLoading method
- (void) connectionDidFinishLoading:(NSURLConnection *)connection {
if (self.responseStatusCode == 200) {
NSLog(#"Succeeded! Received %lu bytes of data",[self.theXML length]);
// Parse the XML into a dictionary
NSError *parseError = nil;
self.xmlDictionary = [XMLReader dictionaryForXMLString:self.theXML options:XMLReaderOptionsProcessNamespaces error:&parseError];
NSLog(#"%#", self.xmlDictionary);
//name of the candidate
self.nameUser = [[[[[[[self.xmlDictionary objectForKey:#"Envelope"] objectForKey:#"Body"] objectForKey:#"GetInterviewResponse"] objectForKey:#"GetInterviewResult"] objectForKey:#"Obj"] objectForKey:#"ProfissionalName"] objectForKey:#"text"];
NSLog(#"User name is: %#", self.nameUser);
TermsViewController *nv = [[TermsViewController alloc] init];
nv.nameUserTerms = self.nameUser;
//check
NSLog(#"User name stored: %#", nv.nameUserTerms);
[self performSegueWithIdentifier:#"goToTerms" sender:self];
}
else {
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:#"Error!"
message:#"bla bla."
delegate:self
cancelButtonTitle:#"Try again"
otherButtonTitles:nil];
[alert show];
}
TermsViewController.m
#import "TermsViewController.h"
#interface TermsViewController ()
#end
#implementation TermsViewController
- (void)viewDidLoad {
[super viewDidLoad];
self.nameLabel.text = self.nameUserTerms;
//this check is returning NULL
NSLog(#"User name: %#", self.nameUserTerms);
}
#end
You should use prepareForSegue to exchange data between controllers.
Remove these lines from your code:
TermsViewController *nv = [[TermsViewController alloc] init];
nv.nameUserTerms = self.nameUser;
And put them in a method like this:
- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
if ([segue.identifier isEqualToString:#"goToTerms"]) {
TermsViewController *nv = segue.destinationViewController;
nv.nameUserTerms = self.nameUser;
}
}
I am writing an iOS app where it counts the steps taken by the user when activated using a button. I am able to count the steps now, but I would like to be able to pause and reset the steps counter by user request. I am not that experienced with XCode, so there might be an easy way to do it. I used a code similar to one available on Stackoverflow:
#import "ViewController.h"
#import "DTStepModelController.h"
#import <CoreMotion/CoreMotion.h>
#interface ViewController ()
#property (weak, nonatomic) IBOutlet UILabel *stepsCountingLabel; #property (nonatomic, strong) CMStepCounter *cmStepCounter;
#property (nonatomic, strong) NSOperationQueue *operationQueue;
#end
#implementation ViewController
{
DTStepModelController *_stepModel;
}
- (NSOperationQueue *)operationQueue
{
if (_operationQueue == nil)
{
_operationQueue = [NSOperationQueue new];
}
return _operationQueue;
}
- (void)updateStepCounterLabelWithStepCounter:(NSInteger)countedSteps
{
self.stepsCountingLabel.text = [NSString stringWithFormat:#"%ld", (long)countedSteps];
}
- (IBAction)StartCountingSteps:(id)sender {
if ([CMStepCounter isStepCountingAvailable])
{
self.cmStepCounter = [[CMStepCounter alloc] init];
[self.cmStepCounter startStepCountingUpdatesToQueue:self.operationQueue updateOn:1 withHandler:^(NSInteger numberOfSteps, NSDate *timestamp, NSError *error)
{
[[NSOperationQueue mainQueue] addOperationWithBlock:^{
[self updateStepCounterLabelWithStepCounter:numberOfSteps];
}];
}];
}
}
Any insight, or suggessions?
I was able to find an answer for my question. Please note that my answer and the previous code in the question will not work if you're using iOS 8.2 or above as Apple discontinue supporting steps counting. In the new iOS version, you can query the M7 counter and save the value, store it, then subtract the new value from the old one.
Anyway, for the above code, you can stop the counter (PauseCounter method) but it will reset the counter to zero.
-(IBAction) PauseCounting: (id) sender {
[self.cmStepCounter stopStepCountingUpdates];
} - (IBAction) ResumeCounting: (id) sender {
[self.cmStepCounter startStepCountingUpdatesToQueue: self.operationQueue updateOn: 1 withHandler: ^ (NSInteger numberOfSteps, NSDate * timestamp, NSError * error) {
[
[NSOperationQueue mainQueue] addOperationWithBlock: ^ {
[self updateStepCounterLabelWithStepCounter: numberOfSteps];
}
];
}];
}
I have class called GlobalArray which is an NSObject. It has an NSArray property called globalData.
I'm passing data into globalData inside of my ViewControllerOne.m, it works perfect, i can print the log in the console. The problem is, that i'm unable to retrieve this data in ViewControllerTwo.m.
GlobalArray.h
#import <Foundation/Foundation.h>
#interface GlobalArray : NSObject
#property (nonatomic, retain) NSArray *globalData; // why retain?
GlobalArray.m
#import "GlobalArray.h"
#implementation GlobalArray
- (id) init
{
self = [super init];
if(self)
{
self.globalData = [[NSArray alloc] init];
}
return(self);
}
ViewControllerOne.m (GlobalArray.h imported into .h)
- (void)viewWillAppear:(BOOL)animated {
[PubNub requestHistoryForChannel:my_channel from:nil to:nil limit:100 reverseHistory:NO withCompletionBlock:^(NSArray *message, PNChannel *channel, PNDate *fromDate, PNDate *toDate, PNError *error) {
GlobalArray *fromHistory = [[GlobalArray alloc] init];
fromHistory.globalData = message;
NSLog(#"TEST LOG 1 %#", fromHistory.globalData);
}];
}
I try to retrieve it in ViewControllerTwo.m this way: (ViewController.h and GlobalArray.h is imported)
-(void) viewWillAppear:(BOOL)animated {
GlobalArray *history = [[GlobalArray alloc] init];
NSArray *sampleArr = [[NSArray alloc] init];
sampleArr = history.globalData;
NSLog(#" TEST LOG2 %#", sampleArr);
}
But TEST LOG2 is empty. I think i missed something in the ViewControllerTwo.m, but can't figure it out, for me it seems it's correct.
If you'd like to avoid the classic Singleton pattern, you can bind a session object to the app delegate and implement the methods to login / logout:
#interface XXXAppDelegate : UIResponder <UIApplicationDelegate>
+ (XXXSession *)loginWithUserName:(NSString*)userName password:(NSString*)password;
+ (void)logout;
+ (XXXSession)currentSession;
#end
Then you define the data managed in your session:
#interface XXXSession : NSObject
#property (nonatomic, retain) NSArray *globalData;
#end
Initialize the session object it in application:didiFinishLaunchingWithOptions: or where it is needed in your application:
#implementation XXXAppDelegate {
XXXSession *_currentSession;
}
- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
[self loginWithUserName: #"Test"];
}
#end
In your ViewControllers you can obtain the session as follow:
[XXXAppDelegate currentSession].globalData
This approach is similar to have a singleton object with the difference that the access to the instance is not offered by the singleton class itself (as stated in the definition of this Design Pattern) but it is implemented in the application delegate.
Of course you'll get empty because you are initializing a separate object of type GlobalArray in your ViewControllerTwo.
This is like you do:
Car car1 = [[Car alloc] init];
car1.name = #"BMW";
Car car2 = [[Car alloc] init];
NSLog(#"Car name = %#", car2.name); <--- this will be empty!
You need to keep the GlobalArray variable somewhere to access it later in ViewControllerTwo instead of reinitializing it, or make the GlobalArray class singleton to always return the same instance instead of creating separate instances.
This question already has answers here:
How do I create delegates in Objective-C?
(20 answers)
Closed 9 years ago.
On iOS, how do I create a delegate (user defined)?
First define a declare a delegate like this -
#protocol IconDownloaderDelegate;
Then create a delegate object like this -
#interface IconDownloader : NSObject
{
NSIndexPath *indexPathInTableView;
id <IconDownloaderDelegate> delegate;
NSMutableData *activeDownload;
NSURLConnection *imageConnection;
}
Declare a property for it -
#property (nonatomic, assign) id <IconDownloaderDelegate> delegate;
Define it -
#protocol IconDownloaderDelegate
- (void)appImageDidLoad:(NSIndexPath *)indexPath;
#end
Then you can call methods on this delegate -
[delegate appImageDidLoad:self.indexPathInTableView];
Here is the complete source code of the image downloader class -
.h file -
#class AppRecord;
#class RootViewController;
#protocol IconDownloaderDelegate;
#interface IconDownloader : NSObject
{
AppRecord *appRecord;
NSIndexPath *indexPathInTableView;
id <IconDownloaderDelegate> delegate;
NSMutableData *activeDownload;
NSURLConnection *imageConnection;
}
#property (nonatomic, retain) AppRecord *appRecord;
#property (nonatomic, retain) NSIndexPath *indexPathInTableView;
#property (nonatomic, assign) id <IconDownloaderDelegate> delegate;
#property (nonatomic, retain) NSMutableData *activeDownload;
#property (nonatomic, retain) NSURLConnection *imageConnection;
- (void)startDownload;
- (void)cancelDownload;
#end
#protocol IconDownloaderDelegate
- (void)appImageDidLoad:(NSIndexPath *)indexPath;
#end
.m file -
#import "IconDownloader.h"
#import "MixtapeInfo.h"
#define kAppIconHeight 48
#define TMP NSTemporaryDirectory()
#implementation IconDownloader
#synthesize appRecord;
#synthesize indexPathInTableView;
#synthesize delegate;
#synthesize activeDownload;
#synthesize imageConnection;
#pragma mark
- (void)dealloc
{
[appRecord release];
[indexPathInTableView release];
[activeDownload release];
[imageConnection cancel];
[imageConnection release];
[super dealloc];
}
- (void)startDownload
{
self.activeDownload = [NSMutableData data];
// alloc+init and start an NSURLConnection; release on completion/failure
NSURLConnection *conn = [[NSURLConnection alloc] initWithRequest:
[NSURLRequest requestWithURL:
[NSURL URLWithString:appRecord.mixtape_image]] delegate:self];
self.imageConnection = conn;
[conn release];
}
- (void)cancelDownload
{
[self.imageConnection cancel];
self.imageConnection = nil;
self.activeDownload = nil;
}
#pragma mark -
#pragma mark Download support (NSURLConnectionDelegate)
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
[self.activeDownload appendData:data];
}
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
// Clear the activeDownload property to allow later attempts
self.activeDownload = nil;
// Release the connection now that it's finished
self.imageConnection = nil;
}
- (void)connectionDidFinishLoading:(NSURLConnection *)connection
{
// Set appIcon and clear temporary data/image
UIImage *image = [[UIImage alloc] initWithData:self.activeDownload];
self.appRecord.mixtape_image_obj = image;
self.activeDownload = nil;
[image release];
// Release the connection now that it's finished
self.imageConnection = nil;
// call our delegate and tell it that our icon is ready for display
[delegate appImageDidLoad:self.indexPathInTableView];
}
#end
and here is how we use it -
#import "IconDownloader.h"
#interface RootViewController : UITableViewController <UIScrollViewDelegate, IconDownloaderDelegate>
{
NSArray *entries; // the main data model for our UITableView
NSMutableDictionary *imageDownloadsInProgress; // the set of IconDownloader objects for each app
}
in .m file -
- (void)startIconDownload:(AppRecord *)appRecord forIndexPath:(NSIndexPath *)indexPath
{
IconDownloader *iconDownloader = [imageDownloadsInProgress objectForKey:indexPath];
if (iconDownloader == nil)
{
iconDownloader = [[IconDownloader alloc] init];
iconDownloader.appRecord = appRecord;
iconDownloader.indexPathInTableView = indexPath;
iconDownloader.delegate = self;
[imageDownloadsInProgress setObject:iconDownloader forKey:indexPath];
[iconDownloader startDownload];
[iconDownloader release];
}
}
here is delegate gets called automatically -
// called by our ImageDownloader when an icon is ready to be displayed
- (void)appImageDidLoad:(NSIndexPath *)indexPath
{
IconDownloader *iconDownloader = [imageDownloadsInProgress objectForKey:indexPath];
if (iconDownloader != nil)
{
UITableViewCell *cell = [self.tableView cellForRowAtIndexPath:iconDownloader.indexPathInTableView];
// Display the newly loaded image
cell.imageView.image = iconDownloader.appRecord.appIcon;
}
}
This is basic concepts to create a own delegate
Delegates are very useful to control transfer within the array of view controllers in app manually. Using delegates you can manage the control flow very well.
here is small example of own delegates....
Create a protocol class.... (.h only)
SampleDelegate.h
#import
#protocol SampleDelegate
#optional
#pragma Home Delegate
-(NSString *)getViewName;
#end
Import above protocol class in the class whom you want to make delegate of another class. Here in my ex. I m using AppDelegate to make delegate of The HomeViewController's Object.
also add above DelegateName in Delegate Reference < >
ownDelegateAppDelegate.h
#import "SampleDelegate.h"
#interface ownDelegateAppDelegate : NSObject <UIApplicationDelegate, SampleDelegate> {
}
ownDelegateAppDelegate.m
//setDelegate of the HomeViewController's object as
[homeViewControllerObject setDelegate:self];
//add this delegate method definition
-(NSString *)getViewName
{
return #"Delegate Called";
}
HomeViewController.h
#import
#import "SampleDelegate.h"
#interface HomeViewController : UIViewController {
id<SampleDelegate>delegate;
}
#property(readwrite , assign) id<SampleDelegate>delegate;
#end
HomeViewController.h
- (void)viewDidAppear:(BOOL)animated {
[super viewDidAppear:animated];
UILabel *lblTitle = [[UILabel alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
lblTitle.text = [delegate getViewName];
lblTitle.textAlignment = UITextAlignmentCenter;
[self.view addSubview:lblTitle];
}