How to format an XLForm row value

Question

I'm using XLForm in my project and want to display the value of one of the rows in a specific format.

The row is "Annual turnover" and I want to display the value entered by the user as a currency - for example, if the user enters 1000000 into the form field, the field should be updated to display this: $ 1,000,000.00

How do I do that?

This is how the form field is initialised in initializeForm():

-(void)initializeForm
{

    // Other fields in the form...

    // Annual turnover Section
    self.section = [XLFormSectionDescriptor formSectionWithTitle:formLabel8AnnualTurnover];
    //section.footerTitle = @"Describe new products";
    [self.formDescriptor addFormSection:self.section];

    // Annual turnover
    self.row = [XLFormRowDescriptor formRowDescriptorWithTag:formField8AnnualTurnover rowType:XLFormRowDescriptorTypeText title:nil];
    self.row.required = NO;
    rowDescriptor8AnnualTurnover = self.row;
    [self.section addFormRow:self.row];

    // Other fields in the form...

    self.form = self.formDescriptor;

}

According to the documentation, I should catch that the user has interacted with the field and then change the value of the field and update the row.

This is how I catch that the user has entered something into the field:

-(void)formRowDescriptorValueHasChanged:(XLFormRowDescriptor *)rowDescriptor oldValue:(id)oldValue newValue:(id)newValue
{
        [super formRowDescriptorValueHasChanged:rowDescriptor oldValue:oldValue newValue:newValue];

        // Get the current form values
        formValues = [self.form formValues];

        int i = 0;

        if ([rowDescriptor.tag hasPrefix:formField8AnnualTurnover]){
                NSString *annualTurnoverValue = [(XLFormOptionsObject*)formValues[formField8AnnualTurnover] displayText];
                rowDescriptor8AnnualTurnover.value = [NSString stringWithFormat:@"R %@", annualTurnoverValue]; //This breaks.
                [self reloadFormRow:rowDescriptor8AnnualTurnover];
            }    
}

Answer 1

An endless loop was being created by resetting the value of the rowDescriptor in formRowDescriptorValueHasChanged.

I resolved this issue by changing formRowDescriptorValueHasChanged to first check whether or not the rowDescriptor's value already starts with the currency symbol, and only add it if it's missing:

-(void)formRowDescriptorValueHasChanged:(XLFormRowDescriptor *)rowDescriptor oldValue:(id)oldValue newValue:(id)newValue
{

   [super formRowDescriptorValueHasChanged:rowDescriptor oldValue:oldValue newValue:newValue];

   // Get the current form values
   formValues = [self.form formValues];
   if ([rowDescriptor.tag hasPrefix:formField8AnnualTurnover]){
        NSString *annualTurnoverValue = [(XLFormOptionsObject*)formValues[formField8AnnualTurnover] displayText];
        if([annualTurnoverValue hasPrefix:@"R "]){
            // Do nothing - the value will simply be increased.
        }else{
            rowDescriptor8AnnualTurnover.value = [NSString stringWithFormat:@"R %@", annualTurnoverValue];
            [self reloadFormRow:rowDescriptor8AnnualTurnover];
        }            
    }    
}