/* 

     File: StockObserver.m 

 Abstract:  Implements a simple object to get stock symbols from the UI and

 register for notifications of price changes of that stock. 

  Version: 1.2 

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 */

#import "StockObserver.h"

extern void AddStockNotificationObserver(const void *observer, CFStringRef stockSymbol);

extern void RemoveStockNotificationObserver(const void *observer, CFStringRef stockSymbol);

extern void RemoveObserverForAllStocks(const void *observer);

@implementation StockObserver

// The callback, as an ObjC method. We put the data in the status area

- (void)stockChanged:(NSString *)stockSymbol newPrice:(double)newPrice {

    NSString *newLine = [NSString stringWithFormat:@"%@ new price: $%.2f\n", stockSymbol, newPrice];

    [[[stockNewsField textStorage] mutableString] appendString:newLine];

}

// The action methods for the "Add" / "Remove" buttons

- (void)addStock:(id)sender {

    NSString *stockSymbol = [stockSymbolField stringValue];

    AddStockNotificationObserver((void *)self, (CFStringRef)stockSymbol);

    [[[stockNewsField textStorage] mutableString] appendFormat:@"Now observing %@\n", stockSymbol];

}

- (void)removeStock:(id)sender {

    NSString *stockSymbol = [stockSymbolField stringValue];

    RemoveStockNotificationObserver((void *)self, (CFStringRef)stockSymbol);

    [[[stockNewsField textStorage] mutableString] appendFormat:@"Stopped observing %@\n", stockSymbol];

}

// When this object is deallocated, it should stop observing; thankfully there's a way to

// quickly remove all observe requests for a given observer

- (void)dealloc {

    RemoveObserverForAllStocks((void *)self);

    [super dealloc];

}

// To assure that this object is deallocated when the app is quitting, we

// listen to the applicationWillTerminate delegate method of the app.

// In more sophisticated, multi-doc apps, we would probably listen to the

// document being closed instead.

- (void)applicationWillTerminate:(NSNotification *)notification {

    [self release];

}

@end

// Callback from AddStockNotificationObserver(). We simply convert the callback

// into an ObjC message send to the right StockObserver object

void StockPriceChanged(void *observer, CFStringRef stockSymbol, double newPrice) {

    [(id)observer stockChanged:(NSString *)stockSymbol newPrice:newPrice];

}