Objective C assigning a dictionary to a variable and accessing it - objective-c

Question

I'm sorry to ask this question again, but I'm still stuck.
I have a city object trying to fetch weather from a weather fetcher object
#interface WeatherFetcher : NSObject {
}
#property (nonatomic, strong) NSMutableDictionary *weatherData;
- (void)fetchWeather:(NSString *)cityName;
- (void)handleNetworkErorr:(NSError *)error;
- (void)handleNetworkResponse:(NSData *)myData;
#end
This is were I assign the value to weatherData
#import "WeatherFetcher.h"
#implementation WeatherFetcher
- (void)fetchWeather:(NSString *)cityName
{
NSString *urlString = #"http://api.openweathermap.org/data/2.5/weather?q=";
urlString = [urlString stringByAppendingString:cityName];
urlString = [urlString stringByAppendingString:#",Aus"];
NSURL *url = [NSURL URLWithString:urlString];
NSURLRequest *request = [[NSURLRequest alloc] initWithURL:url];
[NSURLConnection sendAsynchronousRequest:request
queue:[NSOperationQueue mainQueue]
completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) {
if (connectionError)
{
[self handleNetworkErorr:connectionError];
}
else
{
[self handleNetworkResponse:data];
}
}];
}
#pragma mark - Private Failure Methods
- (void)handleNetworkErorr:(NSError *)error
{
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:#"Network Error" message:#"Please try again later" delegate:nil cancelButtonTitle:nil otherButtonTitles:#"OK", nil];
[alert show];
}
#pragma mark - Private Success Methods
- (void)handleNetworkResponse:(NSData *)myData
{
//NSMutableDictionary *data = [NSMutableDictionary dictionary];
NSMutableDictionary *data = [[NSMutableDictionary alloc] init];
// now we'll parse our data using NSJSONSerialization
id myJSON = [NSJSONSerialization JSONObjectWithData:myData options:NSJSONReadingMutableContainers error:nil];
// typecast an array and list its contents
NSDictionary *jsonArray = (NSDictionary *)myJSON;
//NSLog([jsonArray description]);
// take a look at all elements in the array
for (id element in jsonArray) {
id key = [element description];
id innerArr = [jsonArray objectForKey:key];
NSDictionary *inner = (NSDictionary *)innerArr;
if ([inner conformsToProtocol:#protocol(NSFastEnumeration)]) {
for(id ele in inner) {
if ([ele conformsToProtocol:#protocol(NSFastEnumeration)]) {
NSDictionary *innerInner = (NSDictionary *)ele;
for(id eleEle in innerInner) {
id innerInnerKey = [eleEle description];
[data setObject:[[inner valueForKey:innerInnerKey] description] forKey:[eleEle description]];
}
}
else {
id innerKey = [ele description];
[data setObject:[[inner valueForKey:innerKey] description] forKey:[ele description]];
}
}
}
else {
[data setObject:[inner description] forKey:[element description]];
}
}
self.weatherData = data;
NSLog([self.weatherData description]) **//there is data**
}
#end
However every time I call this from by city object I get nothing back at all.
#import <Foundation/Foundation.h>
#import "WeatherFetcher.h"
#interface City : NSObject {
}
#property (nonatomic, strong) NSString *cityName;
#property (nonatomic, strong) NSString *stateName;
#property (nonatomic, strong) UIImage *cityPicture;
#property (nonatomic, strong) NSString *weather;
#property (nonatomic, strong) NSMutableDictionary *weatherData;
-(NSString *)getWeather;
#end
UI calls getWeather by a button press to get the string value to be displayed on screen
#implementation City {
}
-(NSString *)getWeather {
//return self.weather;
NSString *info = #"";
WeatherFetcher *weatherFetcher = [[WeatherFetcher alloc] init];
[weatherFetcher fetchWeather:self.cityName];
self.weatherData = [weatherFetcher weatherData];
for (id element in self.weatherData) {
info = [info stringByAppendingString:[element description]];
info = [info stringByAppendingString:#"-->"];
info = [info stringByAppendingString:[self.weatherData valueForKey:[element description]]];
info = [info stringByAppendingString:#"\n"];
}
return info;
}
#end
What am I doing wrong here?
getWeather method in the city class gets called when a button is pressed and I'm trying to display this string in a text area. I don't have much experience with Objective C and this is my first app other than Hello World app.
Thank you!

Answer 1

Your WeatherFetcher is asynchronous (sendAsynchronousRequest:) - it sets a task to obtain the data and then returns (usually) before that data has been obtained. So when you try to access the weatherData immediately after the call to fetchWeather: it is not there yet.
You need to redesign your model to handle asynchronicity - getWeather cannot be synchronous. For example you could make fetchWeather: take a completion block to invoke when the data is available and have getWeather pass in a suitable block.