努力与货币在可可粉 [英] Struggling with currency in Cocoa

问题描述

我想做一些我认为相当简单的事情：让用户输入一个美元金额，将该金额存储在NSNumber（NSDecimalNumber？）中，然后在稍后的时间再次显示格式化为货币的金额。

我的麻烦不在于setNumberStyle：NSNumberFormatterCurrencyStyle，并将浮动显示为货币。麻烦更多是如何说明numberFormatter与这个UITextField工作。我可以找到几个例子。 来自十一月的此主题和这一个给我一些想法，但给我更多的问题。

我使用UIKeyboardTypeNumberPad键盘，并且理解我应该在显示时显示$ 0.00（或任何本地货币格式），因为用户输入数字以移动小数位：

• 从显示$ 0.00开始


• 点按2键：display $ 0.02


• 点按5键：display $ 0.25


• 点按4键：display $ 2.54


• 点按3键：display $ 25.43

然后[numberFormatter numberFromString：textField.text]应该给我一个值，我可以存储在我的NSNumber变量。

很抱歉，我还在努力：这是否真的是最好的/最简单的方法？如果是这样，那么也许有人可以帮助我的实现？我觉得UITextField可能需要一个委托响应每个按键，但不知道什么，在哪里和如何实现它？任何示例代码？我非常感谢！ 因此，我正在查找NSFormatter的 stringForObjectValue：。和我可以找到的最接近的事情是什么benzado推荐： UITextViewTextDidChangeNotification 。真的很难在其中任何一个查找示例代码...所以让我知道，如果你知道在哪里看看。

解决方案

我的解决方案：

  
  - （BOOL）textField：（UITextField *）textField 
 shouldChangeCharactersInRange ：（NSRange）range 
 replacementString：（NSString *）string 
 {
 //清除所有不是数字的字符
 //（如货币符号或分隔符）
 NSString * cleanCentString = [[textField.text 
 componentsSeparatedByCharactersInSet：
 [[NSCharacterSet decimalDigitCharacterSet] invertedSet]] 
 componentsJoinedByString：@]; 
 //解析最终整数值
 NSInteger centAmount = cleanCentString.integerValue; 
 //检查用户输入
 if（string.length> 0）
 {
 //添加的数字
 centAmount = centAmount * 10 + string.integerValue; 
} 
 else 
 {
 //删除数字
 centAmount = centAmount / 10; 
} 
 //更新调用金额值
 [_amount release]; 
 _amount = [[NSNumber alloc] initWithFloat：（float）centAmount / 100.0f]; 
 //使用货币符号到文本字段的写入量
 NSNumberFormatter * _currencyFormatter = [[NSNumberFormatter alloc] init]; 
 [_currencyFormatter setNumberStyle：NSNumberFormatterCurrencyStyle]; 
 [_currencyFormatter setCurrencyCode：@USD]; 
 [_currencyFormatter setNegativeFormat：@ - ¤＃，## 0.00]; 
 textField.text = [_currencyFormatter stringFromNumber：_amount]; 
 [_currencyFormatter release] 
 //因为我们已经将我们的更改写入文本字段
 //我们不想再更改文本字段
 return NO; 
} 
 

I'm trying to do something I'd think would be fairly simple: Let a user input a dollar amount, store that amount in an NSNumber (NSDecimalNumber?), then display that amount formatted as currency again at some later time.

My trouble is not so much with the setNumberStyle:NSNumberFormatterCurrencyStyle and displaying floats as currency. The trouble is more with how said numberFormatter works with this UITextField. I can find few examples. This thread from November and this one give me some ideas but leaves me with more questions.

I am using the UIKeyboardTypeNumberPad keyboard and understand that I should probably show $0.00 (or whatever local currency format is) in the field upon display then as a user enters numerals to shift the decimal place along:

• Begin with display $0.00
• Tap 2 key: display $0.02
• Tap 5 key: display $0.25
• Tap 4 key: display $2.54
• Tap 3 key: display $25.43

Then [numberFormatter numberFromString:textField.text] should give me a value I can store in my NSNumber variable.

Sadly I'm still struggling: Is this really the best/easiest way? If so then maybe someone can help me with the implementation? I feel UITextField may need a delegate responding to every keypress but not sure what, where and how to implement it?! Any sample code? I'd greatly appreciate it! I've searched high and low...

Edit1: So I'm looking into NSFormatter's stringForObjectValue: and the closest thing I can find to what benzado recommends: UITextViewTextDidChangeNotification. Having really tough time finding sample code on either of them...so let me know if you know where to look?

解决方案

My solution:

- (BOOL)textField:(UITextField *)textField
    shouldChangeCharactersInRange:(NSRange)range 
    replacementString:(NSString *)string
{
  // Clear all characters that are not numbers
  // (like currency symbols or dividers)
  NSString *cleanCentString = [[textField.text
    componentsSeparatedByCharactersInSet:
    [[NSCharacterSet decimalDigitCharacterSet] invertedSet]]
      componentsJoinedByString:@""];
  // Parse final integer value
  NSInteger centAmount = cleanCentString.integerValue;
  // Check the user input
  if (string.length > 0)
  {
    // Digit added
    centAmount = centAmount * 10 + string.integerValue;
  }
  else
  {
    // Digit deleted
    centAmount = centAmount / 10;
  }
  // Update call amount value
  [_amount release];
  _amount = [[NSNumber alloc] initWithFloat:(float)centAmount / 100.0f];
  // Write amount with currency symbols to the textfield
  NSNumberFormatter *_currencyFormatter = [[NSNumberFormatter alloc] init];
  [_currencyFormatter setNumberStyle:NSNumberFormatterCurrencyStyle];
  [_currencyFormatter setCurrencyCode:@"USD"];
  [_currencyFormatter setNegativeFormat:@"-¤#,##0.00"];
  textField.text = [_currencyFormatter stringFromNumber:_amount];
  [_currencyFormatter release]
  // Since we already wrote our changes to the textfield
  // we don't want to change the textfield again
  return NO;
}

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