「NSCFArray突變而被枚舉」枚舉副本

Question

def leopardRemoveWireless(networkName): 
    plistPath = '/Library/Preferences/SystemConfiguration/preferences.plist' 
    # Sanity checks for the plist 
    if os.path.exists(plistPath): 
    try: 
     pl = NSMutableDictionary.dictionaryWithContentsOfFile_(plistPath) 
    except: 
     print 'Unable to parse file at path: %s' % plistPath 
     sys.exit(1) 
    else: 
    print 'File does not exist at path: %s' % plistPath 
    sys.exit(1) 
    # Create a copy of the dictionary due to emuration 
    copy = NSDictionary.dictionaryWithDictionary_(pl) 
    # Iterate through network sets 
    for Set in copy['Sets']: 
    UserDefinedName = copy['Sets'][Set]['UserDefinedName'] 
    print 'Processing location: %s' % UserDefinedName 

    for enX in copy['Sets'][Set]['Network']['Interface']: 
     print 'Processing interface: %s' % enX 
     # I think this will always be a single key but this works either way 
     for key in copy['Sets'][Set]['Network']['Interface'][enX]: 
     print 'Processing Service: %s' % key 
     # Try to grab the PreferredNetworks key if any 
     try: 
      # Iterate through preferred network sets 
      index = 0 
      for PreferredNetwork in copy['Sets'][Set]['Network']['Interface'][enX][key]['PreferredNetworks']: 
      SSID_STR = PreferredNetwork['SSID_STR'] 
      print 'Processing SSID: %s' % SSID_STR 
      # If the preferred network matches our removal SSID 
      if SSID_STR == networkName: 
       print 'Found SSID %s to remove' % SSID_STR 
       # Delete our in ram copy 
       print 'Processing Set: %s' % Set 
       print 'Processing enX: %s' % enX 
       print 'Processing key: %s' % key 
       del pl['Sets'][Set]['Network']['Interface'][enX][key]['PreferredNetworks'][index] 
      index += 1 
     except KeyError: 
      print 'Skipping interface without PreferredNetworks' 

當我在編輯一個相當複雜的（字典）的plist，然後寫更改回原來的文件後，我找到一個特定的鍵值對錯誤。問題是，即使我做物業的副本列表的字典：

copy = NSDictionary.dictionaryWithDictionary_(pl) 

這是給我的標準「的突變，同時列舉了」錯誤，當我編輯原始的，只是循環鍵作爲獨立插件（注意缺乏引號）。

del pl['Sets'][Set]['Network']['Interface'][enX][key]['PreferredNetworks'][index] 

是我的語法在某種程度上導致它嘗試和編輯pl的字典那麼copy？下面是輸出：

... Processing Set: D5C0A0F4-613A-4121-B6AE-4CBA6E2635FF Processing enX: en1 Processing key: AirPort Traceback (most recent call last): File "/Users/tester/Desktop/wifiutil", line 1164, in sys.exit(main()) File "/Users/tester/Desktop/wifiutil", line 1135, in main removeWireless(osVersion,network) File "/Users/tester/Desktop/wifiutil", line 1051, in removeWireless leopardRemoveWireless(network)
File "/Users/tester/Desktop/wifiutil", line 528, in leopardRemoveWireless for PreferredNetwork in copy['Sets'][Set]['Network']['Interface'][enX][key]['PreferredNetworks']: File "/System/Library/Frameworks/Python.framework/Versions/2.5/Extras/lib/python/PyObjC/objc/_convenience.py", line 431, in enumeratorGenerator yield container_unwrap(anEnumerator.nextObject(), StopIteration) objc.error: NSGenericException - * Collection was mutated while being enumerated.

Answer 1

我認爲這個問題是字典的嵌套性質。 dictionaryWithDictionary_()不會執行任何操作，如深度複製;它所做的就是創建一個新的NSDictionary並複製值的指針（它自己複製密鑰，因爲這是NSDictionary的性質）。

這意味着，雖然你有一個新的頂層，你可以使用枚舉，內部字典和數組是完全一樣的對象爲在原。

你的最後一個循環：

for PreferredNetwork in copy['Sets'][Set]['Network']['Interface'][enX][key]['PreferredNetworks']: 

被列舉出這些內部數組，然後嘗試用del聲明變異之一：

del pl['Sets'][Set]['Network']['Interface'][enX][key]['PreferredNetworks'][index] 

這是不可複製的;它與for中使用的數組對象相同，這會導致異常。您可以通過將這兩個表達式傳遞給id()來測試。

你必須要麼是原始字典的全深拷貝，或（可能更好），你列舉的前幾天最後一級的副本。