Lazy loading example - image

Following image lazy loading example is collected from http://kindlybugs.com/tag/UITableView When using UITableViewController, loading all the images at the beginning is not recommended since it freezes the device for a time. AS a solution, there is another  method called lazy loading.

[Image lazy loading example]

AsyncImage.h

#import <UIKit/UIKit.h>

@interface AsyncImage : UIImageView {

NSURLConnection * connection;

NSMutableData * data;

}

- (void) loadImageFromURLString:(NSString *)theUrlString;

@end

AsyncImage.m

#import "AsyncImage.h"

@implementation AsyncImage

- (void)loadImageFromURLString:(NSString *)theUrlString {

[self.image release], self.image = nil;

NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:theUrlString] 

cachePolicy:NSURLRequestReturnCacheDataElseLoad 

timeoutInterval:30.0];

connection = [[NSURLConnection alloc] initWithRequest:request delegate:self];

if (![NSThread isMainThread])

{

[self performSelectorOnMainThread:@selector(loadImageFromURLString:) withObject:nil waitUntilDone:NO];

return;

}

}

- (void)connection:(NSURLConnection *)theConnection 

didReceiveData:(NSData *)incrementalData 

{

    if (data == nil)

        data = [[NSMutableData alloc] initWithCapacity:2048];

    [data appendData:incrementalData];

}

- (void)connectionDidFinishLoading:(NSURLConnection *)theConnection 

{

    self.image = [UIImage imageWithData:data];

    [data release], data = nil;

[connection release], connection = nil;

}

- (void)dealloc {

[data release];

[connection release];

    [super dealloc];

}

@end

--------------------------- Usage -----------------------

AsyncImage * _asyncImage = [[AsyncImage alloc] initWithFrame:UserFrame];

NSURL * imgURL = [NSURL URLWithString:ImagePath]; 

[_asyncImage loadImageFromURLString:[NSString stringWithFormat:@"%@",imgURL]];