“NSCFArray突变而被枚举”枚举副本

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' 

当我在编辑一个相当复杂的（字典）的plist，然后写更改回原来的文件后，我找到一个特定的键值对错误。问题是，即使我做物业的副本列表的字典：

copy = NSDictionary.dictionaryWithDictionary_(pl) 

这是给我的标准“的突变，同时列举了”错误，当我编辑原始的，只是循环键作为独立插件（注意缺乏引号）。

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

是我的语法在某种程度上导致它尝试和编辑pl的字典那么copy？下面是输出：

... 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

我认为这个问题是字典的嵌套性质。 dictionaryWithDictionary_()不会执行任何操作，如深度复制;它所做的就是创建一个新的NSDictionary并复制值的指针（它自己复制密钥，因为这是NSDictionary的性质）。

这意味着，虽然你有一个新的顶层，你可以使用枚举，内部字典和数组是完全一样的对象为在原。

你的最后一个循环：

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

被列举出这些内部数组，然后尝试用del声明变异之一：

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

这是不可复制的;它与for中使用的数组对象相同，这会导致异常。您可以通过将这两个表达式传递给id()来测试。

你必须要么是原始字典的全深拷贝，或（可能更好），你列举的前几天最后一级的副本。