Question

How do I link live currency exchange rates to my iPhone app? First, anyone know any sites where I can get the exchange rates? And second, how do I link that to my app? I want to do what this app does. http://the-dream.co.uk/currencee/

Answer 1

Here is a blog post about this, however to recap, if you use TBXML you can do it with the methods below.

They do the following:

1. Assume you have made a mutable dictionary object as a class property called exchangeRates
2. Set’s EUR as the base rate (value of 1.0)
3. Call the European Central Bank’s exchange rate XML feed and parses it.

4. After you’ve called the loadExchangeRates() method you can obtain a specific exchange rate by doing:

   NSDecimalNumber *rate = [NSDecimalNumber decimalNumberWithString:[self.exchangeRates objectForKey:@"USD"]];  
   

Here are the methods:

- (void)loadExchangeRates {

// initialize rate array
exchangeRates = [[NSMutableDictionary alloc] init];

// Load and parse the rates.xml file
TBXML * tbxml = [[TBXML tbxmlWithURL:[NSURL URLWithString:@"http://www.ecb.int/stats/eurofxref/eurofxref-daily.xml"]] retain];

// If TBXML found a root node, process element and iterate all children
if (tbxml.rootXMLElement)
    [self traverseElement:tbxml.rootXMLElement];

// add EUR to rate table
[exchangeRates setObject:@"1.0" forKey:@"EUR"];

// release resources
[tbxml release];    }


- (void) traverseElement:(TBXMLElement *)element {

    do {
        // Display the name of the element
        //NSLog(@"%@",[TBXML elementName:element]);

        // Obtain first attribute from element
        TBXMLAttribute * attribute = element->firstAttribute;

        // if attribute is valid
        NSString *currencyName;
        while (attribute) {
            /* Display name and value of attribute to the log window
            NSLog(@"%@->%@ = %@",
                  [TBXML elementName:element],
                  [TBXML attributeName:attribute],
                  [TBXML attributeValue:attribute]);
            */
            // store currency
            if ([[TBXML attributeName:attribute] isEqualToString: @"currency"]) {
                currencyName = [TBXML attributeValue:attribute];
            }else if ([[TBXML attributeName:attribute] isEqualToString: @"rate"]) {
                // store currency and rate in dictionary
                [exchangeRates setObject:[TBXML attributeValue:attribute] forKey:currencyName];
            }
            // Obtain the next attribute
            attribute = attribute->next;
        }

        // if the element has child elements, process them
        if (element->firstChild)
            [self traverseElement:element->firstChild];

        // Obtain next sibling element
    } while ((element = element->nextSibling));
}