Load UILabel Asynchronously using Code Block - ios

Question

I'm stuck with an issue on how to best load a couple of UILabels asynchronously.
Here is my cellForRowAtIndexPath method:
UPDATE:
Based on the answer below, I've made changes:
Here is my new cellForRowAtIndexPath
- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath
{
// Retrieve cell
NSString *cellIdentifier = #"BuildingItem";
BuildingsTableViewCell *cell = [[tableView dequeueReusableCellWithIdentifier:cellIdentifier] initWithFrame:CGRectMake(10, 10,580, 100)];
// Get the area to be shown
Buildings *item = _feedItems[indexPath.row];
NSURL *MyURL = [NSURL URLWithString:item.buildingPointerImage];
UIImage *placeholder = [UIImage imageNamed:#"placeholder"];
NSString *path = [MyURL absoluteString];
NSString *key = [path MD5Hash];
[cell.buildingImageView loadImageFromURL:(NSURL*)MyURL placeholderImage:(UIImage*)placeholder cachingKey:(NSString*)key];
cell.buildingName.text = item.buildingPointerName;
cell.buildingYear.text = item.buildingPointerYear;
NSString *URL = #"http://rets.miamiresidential.com/ios/condos/buildings.php?action=get_range";
NSString *streetNumberURL = [NSString stringWithFormat:#"&street_number=%#",item.buildingStreetNumber];
NSString *streetNameURL = [NSString stringWithFormat:#"&street_name=%#",item.buildingStreetName];
NSString *ZipcodeURL = [NSString stringWithFormat:#"&zipcode=%#",item.buildingZipcode];
NSString *P1 = [URL stringByAppendingString:streetNumberURL];
NSString *P2 = [P1 stringByAppendingString:streetNameURL];
NSString *P3 = [P2 stringByAppendingString:ZipcodeURL];
NSURL *jsonFileUrl = [NSURL URLWithString:P3];
NSLog(#"%#",P3);
[cell.buildingSalesRange loadSalesRangeFromURL:(NSURL*)jsonFileUrl];
[cell.buildingRentalsRange loadRentalsRangeFromURL:(NSURL*)jsonFileUrl];
cell.layer.borderColor = [[UIColor whiteColor]CGColor];
cell.layer.backgroundColor = [[UIColor clearColor]CGColor];
cell.layer.borderWidth = 2;
return cell;
}
and here is my new .m file:
#import "PriceRanges.h"
#import <objc/runtime.h>
#implementation UILabel(Prices)
-(void) loadSalesRangeFromURL:(NSURL*)url {
NSLocale *locale = [[NSLocale alloc] initWithLocaleIdentifier:#"en_US"];
NSNumberFormatter *currencyStyle = [[NSNumberFormatter alloc] init];
[currencyStyle setNumberStyle:NSNumberFormatterCurrencyStyle];
[currencyStyle setLocale:locale];
[currencyStyle setMaximumFractionDigits:0];
NSURLRequest *urlRequest = [[NSURLRequest alloc] initWithURL:url];
[NSURLConnection sendAsynchronousRequest:urlRequest queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *error)
{
if (error)
{
NSLog(#"Error,%#", [error localizedDescription]);
}
else
{
NSArray *priceArray = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingAllowFragments error:&error];
NSNumber *number = [priceArray valueForKeyPath:#"sales.number"];
NSString *lowest = [priceArray valueForKeyPath:#"sales.lowest"];
NSDecimalNumber *lowestDecimal = [NSDecimalNumber decimalNumberWithString:lowest];
NSString *lowestPrice = [currencyStyle stringFromNumber:lowestDecimal];
if (![number isEqualToNumber:[NSNumber numberWithInt:0]]) {
dispatch_async(dispatch_get_main_queue(), ^{
UILabel *labelFromData = [[UILabel alloc] init];
[labelFromData setText:[NSString stringWithFormat:#"%# for Sale from %#",number,lowestPrice]];
if (labelFromData) {
if ([self.text isEqualToString:labelFromData.text]) {
} else {
dispatch_async(dispatch_get_main_queue(), ^{
self.text = labelFromData.text;
});
}
}
self.text = [NSString stringWithFormat:#"%# for Sale from %#",number,lowestPrice];
});
}
};
}];
}
-(void) loadRentalsRangeFromURL:(NSURL*)url {
NSLocale *locale = [[NSLocale alloc] initWithLocaleIdentifier:#"en_US"];
NSNumberFormatter *currencyStyle = [[NSNumberFormatter alloc] init];
[currencyStyle setNumberStyle:NSNumberFormatterCurrencyStyle];
[currencyStyle setLocale:locale];
[currencyStyle setMaximumFractionDigits:0];
NSURLRequest *urlRequest = [[NSURLRequest alloc] initWithURL:url];
[NSURLConnection sendAsynchronousRequest:urlRequest queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *error)
{
if (error)
{
NSLog(#"Error,%#", [error localizedDescription]);
}
else
{
NSArray *priceArray = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingAllowFragments error:&error];
NSNumber *number = [priceArray valueForKeyPath:#"rentals.number"];
NSString *lowest = [priceArray valueForKeyPath:#"rentals.lowest"];
NSDecimalNumber *lowestDecimal = [NSDecimalNumber decimalNumberWithString:lowest];
NSString *lowestPrice = [currencyStyle stringFromNumber:lowestDecimal];
if (![number isEqualToNumber:[NSNumber numberWithInt:0]]) {
dispatch_async(dispatch_get_main_queue(), ^{
[self setText:[NSString stringWithFormat:#"%# for Rent from %#",number,lowestPrice]];
});
}
}
}];
}
#end
As you might see, I have two different methods, but both still send the async request everytime the tables are scrolled.
I guess I am not clear on what to do now?

Answer 1

That's the problem with not having a data model independent of your UI, and a good example of when Model-View-Controller makes sense. You'll need another layer (preferably a separate class) responsible for keeping all the data you've fetched from the network, deciding when it's old enough to discard, etc. The cells should populate themselves from the cached data that the Model keeps, and if the data's not yet present, the model fetches it asynchronously and then notifies the View Controller when the new data arrive. If the cells are still visible, they get populated. If they've scrolled offscreen, been reused, etc, then the data updates don't result in any immediate UI change.