Mac Forum / Programming / Mac Programming / February 2008

I've tried various times/ways of doing it, but none of them seemed to be
"right" - The data got grabbed and parsed, but where/how I did it just
didn't seem to be "correct", and once grabbed, I couldn't figure out
what to do with it next.

I expect that most of the time, the answer would be yes, they're static.
Although I can see the possibility that the app sits idle for long
enough periods for the conversion values (though probably not the
currency names) to fluctuate significantly.

OK, let me bounce some code off you - maybe I understand what you're
saying, maybe I don't. You tell me which is the case!

(I'm deliberately not putting in "boilerplate" stuff to save space.
Assume it's there - in my local code, it is)

CurrencyItem.h

@interface CurrencyItem : NSObject
{
  NSString *currencyName;
  float dollarsPerUnit;
  float unitsPerDollar;
}

// Return a new instance of CurrencyItem, inited with the values
// passed in.
+ (CurrencyItem *)newWithData:(NSString *)theName
              dollarsPerUnit:(float)dpu
              unitsPerDollar:(float)upd;

// Data getters
- (NSString *)name;
- (float)dollarsPerUnit;
- (float)unitsPerDollar;

// Data setters
- (void)setName:(NSString *)theName;
- (void)setDollarsPerUnit:(float)theValue;
- (void)setUnitsPerDollar:(float)theValue;
@end

RateSource.h

@interface RateSource : NSObject
{
  BOOL Initialized;
  NSMutableData *Buffer;
  NSString *TheDate;
}

// Create and return an initialized, but empty, RateSource object.
+ (RateSource *)New;

// Finalize initializing a RateSource instance.
- (RateSource *)init;

// Fill the array passed to us with CurrencyItem objects parsed from
// the data we get from the website. Return the timestamp for the data
// as an NSString.
- (NSString *)fillArray:(NSMutableArray *)TheArray;

// Many lines of irrelevant (to this question) instance methods
// involved with parsing the HTML the website returns, building
// CurrencyItem objects using the parsed data, and stuffing those
// objects into the array elided to save space.
@end

Given these two interfaces, it *SOUNDS LIKE* you're saying I need my
controller to look similar to this:

MyController.h

@interface MyController:NSObject
{
  // various other (not relevant to this question) instance variables

  IBOutlet NSPopUpButton *Menu1;
  IBOutlet NSPopUpButton *Menu2;
  NSMutableArray *myArray;
}

// various irrelevant methods elided

- (void) awakeFromNib;
@end

MyController.m

@implementation myController

// other methods...

- (void)awakeFromNib
{
  CFIndex counter;
  RateSource *rateSource = [RateSource New];

  // Perhaps much "other stuff", eventually leading to...
 
  myArray = [NSMutableArray arrayWithCapacity:0];
  // Get the data from the website
  dataTimestamp = [rateSource fillArray:myArray];
  // Now I think I need to populate the menus with the data
  // that RateSource stuffed into myArray - right?
  // Here's where I get confused...
  // How do I instantiate "Menu1" and "Menu2"?
  // Or do they already exist as ready-to-use objects when I
  // reach this point?
  // I'll assume that they do indeed exist, and that
  // I can simply go to work on them. If that's not the case,
  // PLEASE clue me as to how to "make" them.
  [Menu1 removeAllItems]; // Empty out IB's placeholder items
  [Menu2 removeAllItems]; // ditto
  for (counter = 0; counter < [myArray count]; counter++)
   {
     [Menu1 addItemWithTitle:[[myArray objectAtIndex:counter] name]];
     [Menu2 addItemWithTitle:[[myArray objectAtIndex:counter] name]];
   }
}
@end

"Ding" indeed... I'm thinking that the code above should do it - *IF*
I'm understanding what you've said correctly. Time for some testing...

(Time passes)

Uh-oh...

I've managed to break SOMETHING, it looks like. Got everything to
compile and link with zero warnings or errors, however, trying to run
the program to see if it's working does *ABSOLUTELY NOTHING*. No
bouncing icon in the dock, no earth-shattering kaboom, no nothing.

<sigh> I wonder what I've got wrong this time?

Back to the drawing board... Wuddayawannabet I mangled something while
re-creating the project that I foolishly trashed due to utter
frustration?

Greg managed to beat that into my thick skull :) I think I've got it,
now. (and hopefully "forever"!)

Except that, at the time I wrote that, I didn't quite grok the "add an
outlet" part.

Between you and Greg "double-teaming" me with it, that concept has
finally penetrated. And it works. Hooray! :)

A little beyond me right now, I'm thinking - Do please keep in mind that
prior to about Xmas eve, the only thing I knew about Objective C and/or
Cocoa could be summed up in *EXACTLY* two words. Those two words?

"It exists"

Maybe I'll "get there" some day, though :)
(But not before I manage to scrape together enough spare pennies to
upgrade to a newer kitty-cat than my current Panther, obviously...)

Yep, that's what I've done for now.

I bumbled onto that concept somewhere about New Years Day, took one
look, and fled screaming in abject terror... As I said above, "Maybe
I'll get there some day" :)

Meanwhile, this is supposed to be a success report!

And I'm happy to report that I do indeed have exactly correct
functionality! A few tweaks to the code in my previous message in the
thread (and *PROPERLY* re-creating the project... I botched something in
the first attempt, apparently) got me rolling.

Now I'm fully able to populate the menus (via the awakeFromNib method in
my controller object) and my "convert" action (also in the controller)
properly queries the individually.

One more comment:
Back around New Year's Eve, I tried (and failed) with something *VERY*
similar to what ended up working. The difference? In IB, I was trying to
connect *FROM* the NSPopUpButtons *TO* the "MyController" instance, and
failing every time because there was nothing to connect to. No matter
what I did, I couldn't figure out how to connect the button to the
controller. This time around, I went the other way - Connect *FROM* the
controller *TO* the button, and everything works as planned. D'OH!

Thanks for the help, guys!

Just in case anybody's interested, here's what I ended up with in my
controller class - a total of somewhere in the neighborhood of 65 lines
of code, counting comments and vertical whitespace. I guess Objective C
really CAN be compact!

/* MyController.h */

#import <Cocoa/Cocoa.h>
#import "Converter.h"

@interface MyController : NSObject
{
   IBOutlet Converter *converter;
   IBOutlet NSTextField *input;
   IBOutlet NSPopUpButton *Menu1;
   IBOutlet NSPopUpButton *Menu2;
   IBOutlet NSTextField *output;
 
   NSString *dataTimestamp; // holds the "generated on" timestamp
   NSMutableArray *myArray; // holds currency names and exchange rates
}
- (IBAction)Convert:(id)sender;
- (void)awakeFromNib;

@end

And of course, the actual code... (I expect some lines are going to wrap
- beware...)

/* MyController.m */
#import "MyController.h"
#include "Converter.h"
#import "RateSource.h"
#import "CurrencyItem.h"

@implementation MyController

- (IBAction)Convert:(id)sender
{
  // extract the source currency's dollars per unit value
  float DPU = [[myArray objectAtIndex:[Menu1 indexOfSelectedItem]]
dollarsPerUnit];
  // extract the target currency's units per dollar value
  float UPD = [[myArray objectAtIndex:[Menu2 indexOfSelectedItem]]
unitsPerDollar];
  // Convert the input value into dollars
  float DollarValue = [converter ConvertInputToDollars:[input
floatValue] Rate:DPU];
  // Convert the intermediate dollar value into the output value
  float OutputValue = [converter ConvertDollarsToOutput:DollarValue
Rate:UPD];

  // And finally, stuff the output field with the resulting number
  [output setFloatValue:OutputValue];
}

- (void)awakeFromNib
{
  CFIndex counter;
  RateSource *rateSource = [RateSource New];
 
  myArray = [NSMutableArray arrayWithCapacity:0];
  // Hmmm... apparently I have to hold on to it via retain
  // If I don't, Convert barfs.
  [myArray retain];
  // Get the data from the website
  dataTimestamp = [rateSource fillArray:myArray];
  converter = [Converter New];
  // Ditto - Convert barfs if I don't explicitly retain. Interesting...
  [converter retain];
  // Now stuff the menus with the currency names from myArray.
  [Menu1 removeAllItems]; // Empty out IB's placeholder items
  [Menu2 removeAllItems]; // ditto
  for (counter = 0; counter < [myArray count]; counter++)
   {
     [Menu1 addItemWithTitle:[[myArray objectAtIndex:counter] name]];
     [Menu2 addItemWithTitle:[[myArray objectAtIndex:counter] name]];
   }
}
@end

hi how to display the video in the window