当输入 NSDictionary 时，属性列表中的空白值被视为什么？
假设我有一个存储到 NSDictionary 中的属性列表。 NSLog 的输出示例如下：
2010-12-05 15:26:26.631 TestApp[598:207] Test contents: {
Address = "";
Name = "Test Dictionary";
Address 的值究竟会被考虑什么？我听说过很多可能性，但我不确定。是NSNull，nil，什么？我最终想做的是创建第二个 NSDictionary 来过滤掉所有这些空白值，如 此处。但首先，我需要弄清楚空白值被算作什么，这样我就可以解析它们的 plist，然后折扣与它们关联的键。
Say I have a property list that I store into an NSDictionary. An example output from NSLog follows:
2010-12-05 15:26:26.631 TestApp[598:207] Test contents: {
Address = "";
Name = "Test Dictionary";
What exactly would the value for Address be considered? I have heard many possibilities, but I'm not sure exactly. Is it NSNull, nil, what? What I would ultimately like to do is to create a second NSDictionary that filters out all of these blank values, as seen here. But first, I need to figure out what the blank value is counted as, so then I can parse my plist for them, and then discount the keys associated with them.
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空字符串是字符串，而不是 NSNull 或 nil。因此，一种测试方法是
[@"" isEqualToString: thevalue]。An empty string is a string, not NSNull or nil. So one way to test would be
[@"" isEqualToString: thevalue].