將NSString轉換爲NSDecimalNumber

Question

在我的核心數據模型中，「amount」是實體「Tracking」中的一個屬性。如何在整個代碼中將金額轉換爲NSDecimalNumber？我相信有更多經驗的人可以在3分鐘內做到這一點，我已經看了好幾天。

- (IBAction)save { 
if (![amount.text isEqualToString:@""]) { 
Tracking *tracking = [NSEntityDescription insertNewObjectForEntityForName:@"Tracking" 
               inManagedObjectContext:self.managedObjectContext]; 

    NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; 
    NSEntityDescription *weightEntity = [NSEntityDescription entityForName:@"Tracking" inManagedObjectContext:self.managedObjectContext]; 
    [fetchRequest setEntity:weightEntity]; 
    NSSortDescriptor *sortDescriptor = [NSSortDescriptor sortDescriptorWithKey:@"timestamp" ascending:NO]; 
    [fetchRequest setSortDescriptors:[NSArray arrayWithObject:sortDescriptor]]; 

    NSError *error = nil; 
    NSArray *result = [self.managedObjectContext executeFetchRequest:fetchRequest error:&error]; 

    Tracking *person = [result objectAtIndex:0]; 

    NSLog(@"%@",person.date); 

     NSDate *date = [NSDate date]; 
    NSDateFormatter *dateFormat = [[NSDateFormatter alloc]init]; 
    [dateFormat setDateFormat:@"MMM dd, yyyy"]; 

    NSString *dateString = [dateFormat stringFromDate:date]; 
    //NSString *dateString = @"Jan 13 2013"; 
    //Tracking *track = [self.fetchedResultsController objectAtIndexPath:nil]; 

tracking.note = note.text; 
tracking.amount = amount.text; 
tracking.title = [segmentedChoice titleForSegmentAtIndex:segmentedChoice.selectedSegmentIndex]; 
tracking.date = dateString; 
tracking.timestamp = date; 

     if (![person.date isEqualToString:dateString]) { 

     if ([[segmentedChoice titleForSegmentAtIndex:segmentedChoice.selectedSegmentIndex] isEqualToString:@"Food/Drink"]) { 
      tracking.pic = @"Drink"; 
      tracking.total = [NSString stringWithFormat:@"%.2f", 0.00 - [amount.text floatValue]]; 
      NSLog(@"%f",[person.total floatValue]); 
      NSLog(@"%f", [amount.text floatValue]); 
      //tracking.total = @"1000.00"; 
     } 
     else if ([[segmentedChoice titleForSegmentAtIndex:segmentedChoice.selectedSegmentIndex] isEqualToString:@"Other"]) { 
      tracking.total = [NSString stringWithFormat:@"%.2f",0.00 - [amount.text floatValue]]; 
      tracking.pic = [segmentedChoice titleForSegmentAtIndex:segmentedChoice.selectedSegmentIndex]; 

     } 

     else { 
      tracking.pic = [segmentedChoice titleForSegmentAtIndex:segmentedChoice.selectedSegmentIndex]; 
      tracking.total = [NSString stringWithFormat:@"%.2f",0.00 + [amount.text floatValue]]; 
     } 

    } 

    else { 


     if ([[segmentedChoice titleForSegmentAtIndex:segmentedChoice.selectedSegmentIndex] isEqualToString:@"Food/Drink"]) { 
      tracking.pic = @"Drink"; 
      tracking.total = [NSString stringWithFormat:@"%.2f",[person.total floatValue] - [amount.text floatValue]]; 
      NSLog(@"%f",[person.total floatValue]); 
      NSLog(@"%f", [amount.text floatValue]); 
    //tracking.total = @"1000.00"; 
      } 
     else if ([[segmentedChoice titleForSegmentAtIndex:segmentedChoice.selectedSegmentIndex] isEqualToString:@"Other"]) { 
      tracking.total = [NSString stringWithFormat:@"%.2f",[person.total floatValue] - [amount.text floatValue]]; 
      tracking.pic = [segmentedChoice titleForSegmentAtIndex:segmentedChoice.selectedSegmentIndex]; 

     } 

     else { 
      tracking.pic = [segmentedChoice titleForSegmentAtIndex:segmentedChoice.selectedSegmentIndex]; 
      tracking.total = [NSString stringWithFormat:@"%.2f",[person.total floatValue] + [amount.text floatValue]]; 

     } 
    } 

NSLog(@"\n Title: %@ \n Amount: %@ \n Note: %@ \n Date: %@ \n Picture: %@.png \n Total: %@ \n TimeStamp: %@", tracking.title, tracking.amount, tracking.note,tracking.date,tracking.pic, tracking.total, tracking.timestamp); 

    [self.managedObjectContext save:nil]; 

    /* UIAlertView *alert = [[UIAlertView alloc] initWithTitle:[NSString stringWithFormat:@"%@ Saved",tracking.title] message:[NSString stringWithFormat:@"Amount: %@ \n Note: %@",tracking.amount,tracking.note] delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil, nil]; 
    [alert show];*/ 

    [amount resignFirstResponder]; 
    [note resignFirstResponder]; 
    [self dismissViewControllerAnimated:YES completion:nil]; 
} 

Answer 1

NSDecimalNumber有以下方法，你可以用你的NSString轉換成它：

+ (NSDecimalNumber *)decimalNumberWithString:(NSString *)numericString 

例如：

NSString *foo = @"1.0"; 
NSDecimalNumber *cow = [NSDecimalNumber decimalNumberWithString:foo]; 

類的

完整參考，請訪問：http://developer.apple.com/library/mac/#documentation/Cocoa/Reference/Foundation/Classes/NSDecimalNumber_Class/Reference/Reference.html#//apple_ref/occ/cl/NSDecimalNumber

Answer 2

這裏你去：

NSString *order; 
NSDecimalNumber *decimal = [NSDecimalNumber decimalNumberWithString:order];