Pause function while JSON call is running - ios

Question

I would like my save button to run the JSON call and then finish it's function, but it finishes the function while running the JSON call, so the variables become initialized as nil.
My DeviceDetailViewController.m
//
// DeviceDetailViewController.m
// Steam Backpack Viewer
//
// Created by Vishwa Iyer on 5/22/14.
// Copyright (c) 2014 MoAppsCo. All rights reserved.
//
#import "DeviceDetailViewController.h"
#import "MasterViewController.h"
#import "ProfileManager.h"
#import "ProfileCommunicator.h"
#import "SteamProfile.h"
#import "DeviceViewController.h"
#interface DeviceDetailViewController () <ProfileManagerDelegate> {
ProfileManager *_manager;
NSArray *profile;
SteamProfile *s;
}
extern NSString *ID;
#end
#implementation DeviceDetailViewController
- (NSManagedObjectContext *)managedObjectContext {
NSManagedObjectContext *context = nil;
id delegate = [[UIApplication sharedApplication] delegate];
if ([delegate performSelector:#selector(managedObjectContext)]) {
context = [delegate managedObjectContext];
}
return context;
}
- (IBAction)cancel:(id)sender {
[self dismissViewControllerAnimated:YES completion:nil];
}
- (IBAction)save:(id)sender {
NSManagedObjectContext *context = [self managedObjectContext];
// Create a new managed object
NSManagedObject *newDevice = [NSEntityDescription insertNewObjectForEntityForName:#"BackpackViewer" inManagedObjectContext:context];
[newDevice setValue:self.steamIDTextField.text forKey:#"steamID"];
ID = [NSString stringWithFormat:#"%#", [newDevice valueForKey:#"steamID"]];
[self startFetchingGroups]; // I would like this JSON call to finish before calling the rest of the function below
[newDevice setValue:s.personaname forKey:#"steamName"];
[newDevice setValue:s.avatar forKey:#"imageURL"];
NSError *error = nil;
// Save the object to persistent store
if (![context save:&error]) {
NSLog(#"Can't Save! %# %#", error, [error localizedDescription]);
}
[self dismissViewControllerAnimated:YES completion:nil];
}
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
// Custom initialization
}
return self;
}
- (void)viewDidLoad
{
[super viewDidLoad];
_manager = [[ProfileManager alloc] init];
_manager.communicator = [[ProfileCommunicator alloc] init];
_manager.communicator.delegate = _manager;
_manager.delegate = self;
// Do any additional setup after loading the view.
}
- (void)startFetchingGroups
{
[_manager fetchGroups];
}
- (void)didReceieveProfileInfo:(NSArray *)groups
{
//the JSON call finishes here, when the groups are receives from the call. I would then like the rest of the save button method above to run after this runs, so that the s variable (which corresponds to a SteamProfile object) becomes initialized correctly.
profile = groups;
s = [profile objectAtIndex:0];
NSLog(s.personaname);
}
- (void)fetchingGroupsFailedWithError:(NSError *)error
{
NSLog(#"Error %#; %#", error, [error localizedDescription]);
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
#end

Answer 1

I think you looking for something like this. Note this syntax could be wrong it is untested. I will leave it to you to read the documentation on function call backs.
#interface MyClass: NSObject
{
void (^_completionHandler)(int someParameter);
}
- (void)startFetchingGroups:(void(^)(int))handler;
#end
#implementation MyClass
- (void)startFetchingGroups:(void(^)(void))handler
{
[_manager fetchGroups];
if (handler) {
handler();
}
}
#end
[var startFetchingGroups:^{
[newDevice setValue:s.personaname forKey:#"steamName"];
[newDevice setValue:s.avatar forKey:#"imageURL"];
NSError *error = nil;
// Save the object to persistent store
if (![context save:&error]) {
NSLog(#"Can't Save! %# %#", error, [error localizedDescription]);
}
[self dismissViewControllerAnimated:YES completion:nil];
}];
The behavior of when a callback gets called depends on what the _manager fetchGroups actually does. You could also use delegation as some of the people in the comments suggested, and is definatly a clean solution as well.

Answer 2

Sorry for ugly formatting. This code does exactly what you want..
#import "DeviceDetailViewController.h"
#import "MasterViewController.h"
#import "ProfileManager.h"
#import "ProfileCommunicator.h"
#import "SteamProfile.h"
#import "DeviceViewController.h"
typedef void(^EmptyBlock_t)();
#interface DeviceDetailViewController () <ProfileManagerDelegate> {
ProfileManager *_manager;
NSArray *profile;
SteamProfile *s;
// 1
// here you define a block, an anonymous function pointer that will be called right after you callback is called..
EmptyBlock_t _blockAfterJSONFetched;
}
extern NSString *ID;
#end
#implementation DeviceDetailViewController
- (NSManagedObjectContext *)managedObjectContext {
NSManagedObjectContext *context = nil;
id delegate = [[UIApplication sharedApplication] delegate];
if ([delegate performSelector:#selector(managedObjectContext)]) {
context = [delegate managedObjectContext];
}
return context;
}
- (IBAction)cancel:(id)sender {
[self dismissViewControllerAnimated:YES completion:nil];
}
- (IBAction)save:(id)sender {
NSManagedObjectContext *context = [self managedObjectContext];
// Create a new managed object
NSManagedObject *newDevice = [NSEntityDescription insertNewObjectForEntityForName:#"BackpackViewer" inManagedObjectContext:context];
[newDevice setValue:self.steamIDTextField.text forKey:#"steamID"];
ID = [NSString stringWithFormat:#"%#", [newDevice valueForKey:#"steamID"]];
[self startFetchingGroups]; // I would like this JSON call to finish before calling the rest of the function below
// 2
// here you assign a value to your block. Notice that all objects inside block are called "retain" automatically. Also they a called "release" when you release the block itself..
_blockAfterJSONFetched=^{
[newDevice setValue:s.personaname forKey:#"steamName"];
[newDevice setValue:s.avatar forKey:#"imageURL"];
NSError *error = nil;
// Save the object to persistent store
if (![context save:&error]) {
NSLog(#"Can't Save! %# %#", error, [error localizedDescription]);
}
[self dismissViewControllerAnimated:YES completion:nil];
};
}
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self) {
// Custom initialization
}
return self;
}
- (void)viewDidLoad
{
[super viewDidLoad];
_manager = [[ProfileManager alloc] init];
_manager.communicator = [[ProfileCommunicator alloc] init];
_manager.communicator.delegate = _manager;
_manager.delegate = self;
// Do any additional setup after loading the view.
}
- (void)startFetchingGroups
{
[_manager fetchGroups];
}
- (void)didReceieveProfileInfo:(NSArray *)groups
{
//the JSON call finishes here, when the groups are receives from the call. I would then like the rest of the save button method above to run after this runs, so that the s variable (which corresponds to a SteamProfile object) becomes initialized correctly.
profile = groups;
s = [profile objectAtIndex:0];
NSLog(s.personaname);
// 3
// finally after your callback is fired you check if block pointer is not null and if it is you call it as a casual function. Assigning nil in the end is optional..
if(_blockAfterJSONFetched){
_blockAfterJSONFetched();
_blockAfterJSONFetched=nil;
}
}
- (void)fetchingGroupsFailedWithError:(NSError *)error
{
NSLog(#"Error %#; %#", error, [error localizedDescription]);
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
#end