Google providing REST URI for currency calculator
http://www.google.com/ig/calculator?hl=en&q=
10USD=?
INR
We have to pass the above two arguments to get JSON result
{lhs: "10 U.S. dollars",rhs: "536.912752 Indian rupees",error: "",icc: true}
The above returned JSON is invalid so convert into a valid JSON by adding '"' to lhs , rhs, error and icc.
How to handle JSON in iOS5 and later:
NSJSONSerialization class used to convert JSON to Foundation objects like NSDictionary, NSArray etc and vice versa. It is only available iOS5 and above.
NSDictionary* json = [NSJSONSerialization
JSONObjectWithData:data
options:kNilOptions
error:&error]; //data is NSData sent from google server
now get the resulted json in NSDictionary then we can get the result by giving the key.
NSString* convertedvalue = [json objectForKey:@"rhs"];
Difference between NSURLConnection and NSData initWithContentsOfURL :-
NSURLConnection is a asynchronous request by default , it will start a thread automatically and delegates are called from that thread.
Also NSURLConnection has a convenience class method, sendSynchronousRequest:returningResponse:error:, to load a URL request synchronously.
NSData initWithCOntentsOfURL is a synchronous method call ,so it will block the thread.
Better use dispatch_async block to run the code in separate thread, once operation completed call the main thread.
 |
iphone
Currency converter |
- (IBAction)convertButtonCLicked:(UIButton *)sender {
if([self.progressIndicator isAnimating] == NO)
{
if(self.amountTxtField.text.length > 0 && self.fromTxtField.text.length >0 && self.toTxtField.text.length > 0)
{
[self.progressIndicator startAnimating];
dispatch_queue_t downloadQueue = dispatch_queue_create("google downloader", NULL);
dispatch_async(downloadQueue, ^{
NSString* amount =self.amountTxtField.text;
NSString *fromstr = self.fromTxtField.text ;
NSRange fromrange ;
fromrange.length = 3;
fromrange.location = fromstr.length - 4;
fromstr = [fromstr substringWithRange:fromrange];
NSString *tostr = self.toTxtField.text ;
NSRange torange ;
torange.length = 3;
torange.location = tostr.length -4;
tostr = [tostr substringWithRange:torange];
NSString *urlAddress = [[NSString alloc] initWithFormat:GOOGLERESTURL,[NSString stringWithFormat:@"%@%@",amount,fromstr],tostr];
NSString* escapedUrlString =
[urlAddress stringByAddingPercentEscapesUsingEncoding:
NSUTF8StringEncoding];
NSData* data = [NSData dataWithContentsOfURL:
[NSURL URLWithString:escapedUrlString]];
[self performSelectorOnMainThread:@selector(updateConvertedValue:)
withObject:data waitUntilDone:YES];
});
dispatch_release(downloadQueue);
}
else {
[self alertMessage:@"Enter all values !"];
}
}
}
-(void)updateConvertedValue: (NSData*)receivedData
{
NSString *result = [[NSString alloc] initWithBytes:[receivedData bytes] length:[receivedData length] encoding:NSUTF8StringEncoding];
NSError *error = NULL;
//google is not sending valid JSOn so convert into valid JSON
NSString *resultdata = result;
resultdata = [resultdata stringByReplacingOccurrencesOfString:@"{" withString:@"{\""];
resultdata = [resultdata stringByReplacingOccurrencesOfString:@"," withString:@",\""];
resultdata = [resultdata stringByReplacingOccurrencesOfString:@":" withString:@"\":"];
NSData* data = [resultdata dataUsingEncoding:NSUTF8StringEncoding];
NSDictionary* json = [NSJSONSerialization
JSONObjectWithData:data
options:kNilOptions
error:&error];
NSString* convertedvalue = [json objectForKey:@"rhs"];
if(error == nil)
outputLabel.text = convertedvalue;
else {
outputLabel.text = @"conversion not available";
}
[self.progressIndicator stopAnimating];
}
