vbscript 字典添加循环产生现有键错误

发布于 2024-11-24 16:48:21 字数 466 浏览 3 评论 0原文

我只是想构造一个productIDs 字典

dim viewableProductIDs : set viewableProductIDs = CreateObject("Scripting.Dictionary")
    do while not rsEntry.EOF
        viewableProductIDs.Add rsEntry("ProductID"), true
        rsEntry.MoveNext
    loop

rsEntry 是一个ADODB 记录集，并且通过详尽的调试打印，我已经确保我的查询确实返回唯一的productIDs 并且记录集没有重复项。但不知何故，vbscript 坚持认为存在重复项。它会很好地添加第一个，但之后所有其余的都会出错。我尝试用检查现有密钥来包围它，它以某种方式认为它们都存在，但第一个存在。最后我只剩下一本只有一个条目的字典。

有谁知道它为什么这样做？

原文

I'm simply trying to construct a dictionary of productIDs

dim viewableProductIDs : set viewableProductIDs = CreateObject("Scripting.Dictionary")
    do while not rsEntry.EOF
        viewableProductIDs.Add rsEntry("ProductID"), true
        rsEntry.MoveNext
    loop

rsEntry is a ADODB Recordset and I have made sure, through exhaustive debbug printing, that my query is indeed returning unique productIDs and that the recordset has no duplicates. Yet someohow, vbscript insists on thinking there are duplicates. It'll add the first one fine, but after that it errors out on all the rest. I tried surrounding it with a check for existing key and it someohow thought they all, but the first, existed. Then in the end I'm left with a dictionary with only one entry in it.

Does anyone have any idea as to why it's doing this?

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暖心男生 2024-12-01 16:48:21

尝试添加.Value：

viewableProductIDs.Add rsEntry("ProductID").Value, true

说明：

VBScript 有一个称为“默认”属性的概念。例如，该行

someString = rsEntry("ProductID")

的简写

someString = rsEntry.Fields.Item("ProductID").Value

实际上是Fields、Item 和 Value 都是其各自对象的默认属性。这里的主要问题在于该链的最后一步：rsEntry("ProductID") 和 rsEntry("ProductID").Value 之间的差异。在上面的示例中，由于我没有使用 Set 关键字，因此对象引用对于赋值的右侧来说是非法的。由于 rsEntry("ProductID") 计算结果为 Field 对象引用，因此解释器将执行下一步并扩展 Field 对象的默认属性，值。如果我这样做了，

Set someObj = rsEntry("ProductID")

解释器会将 someObj 设置为 Field 对象引用。

现在有趣的部分是：Dictionary 对象可以使用任何类型的值作为其键。使用字符串或数字等简单值更为常见，但使用数组或对象引用是完全合法的。由于对象引用对于 Dictionary.Add 方法的第一个参数是合法的，因此解释器不会费心扩展默认属性，而只是使用 Field 对象引用作为关键。由于 Field 对象引用不会因记录而改变，因此您最终会尝试一遍又一遍地添加相同的键。添加 .Value 可以让解释器明确知道您需要的是值，而不是对象。

Try adding .Value:

viewableProductIDs.Add rsEntry("ProductID").Value, true

Explanation:

VBScript has a concept called "default" properties. For instance, the line

someString = rsEntry("ProductID")

really is shorthand for

someString = rsEntry.Fields.Item("ProductID").Value

where Fields, Item, and Value are all the default properties of their respective objects. The main problem here is in the last step of the chain: the difference between rsEntry("ProductID") and rsEntry("ProductID").Value. In the above example, since I didn't use the Set keyword, an object reference would be illegal for the right-hand side of the assignment. Since rsEntry("ProductID") evaluates to a Field object reference, the interpreter takes the next step and expands the default property of the Field object, Value. If I had done

Set someObj = rsEntry("ProductID")

the interpreter would have set someObj to the Field object reference.

Now here's the fun part: the Dictionary object can use any type of value as its keys. It's more common to use simple values like strings or numbers, but it's perfectly legal to use arrays or object references. Since an object reference is legal for the first argument of the Dictionary.Add method, the interpreter doesn't bother to expand the default property and simply uses the Field object reference as the key. Since the Field object reference doesn't change from record to record, you end up trying to add the same key over and over. Adding .Value makes it explicitly clear to the interpreter that you want the value, not the object.

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