Modifying array within Dictionary is ignored

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The following code:

Dim arr As Variant, item As Variant
arr = Array(1)
arr(0) = 5
For Each item In arr
    Debug.Print item
Next

prints 5; it seems to successfully modify the contents of the array.

However, if I create a Dictionary, and place an array at one of the dictionary keys:

Dim dict As New Scripting.Dictionary, item As Variant
dict("a") = Array(1)
dict("a")(0) = 5
For Each item In dict("a")
    Debug.Print item
Next

the array is read-only; the edit is ignored, and the code prints 1 -- the original value.

Why can I modify the elements of an array referenced through a variable, but not those of an array referenced through a call to Dictionary.Item; and how can I resolve this?


Here is working example with dictionary:

Sub Test()

    Dim dict As New Scripting.Dictionary, item As Variant
    dict("a") = Array(1)
    Dim arr
    arr = dict("a")
    arr(0) = 5
    dict("a") = arr
    For Each item In dict("a")
        Debug.Print item
    Next

End Sub

And also take a look at nested arrays:

Sub TestArrays()

    Dim a() As Variant, item As Variant
    a = Array("")
    a(0) = Array(1)
    a(0)(0) = 5
    For Each item In a(0)
        Debug.Print item
    Next

End Sub

A question about modifying Arrays and Dictionaries., What's your definition of "not working"? Did you create dictionaries and arrays by writing Array() or Dictionary() by any chance? (instead of [] or  In Python, a nested dictionary is a dictionary inside a dictionary. It's a collection of dictionaries into one single dictionary. Here, the nested_dict is a nested dictionary with the dictionary dictA and dictB. They are two dictionary each having own key and value.


Just to clarify your questions with an example expanding on @omegastripes answer and my comments on referencing variables in VBA

COMMENTS: You're setting the value of the dictionary. You're NOT setting the value of the array item. You cannot set the dictionary item to a reference to the array - you can set an array value then set the dictionary to the array item - but that is using the value not the reference

Here's an example to show that VBA does not store a reference to the variable when you assign it to another variable

Sub Test()

    Dim dict As Object, item As Variant

    Dim arr

    Set dict = CreateObject("Scripting.Dictionary")

    dict("a") = Array(1)

    arr = dict("a")
    arr(0) = 5
    dict("a") = arr
    For Each item In dict("a")
        Debug.Print item
        ' Prints 5
    Next

    ' Change array contents
    arr(0) = 10
    For Each item In dict("a")
        Debug.Print item
        ' Still Prints 5
    Next

End Sub

Results in Immediate Window will be:

5
5

20. Dictionaries, In other languages, they are called associative arrays since they associate a key with a value. As an example, we will The key:value pairs of the dictionary are separated by commas. Each pair If we want to modify a dictionary and keep a copy of the original, use the copy method. Case should be ignored. A sample  As you can see, the property Title is always ignored and the property FirstName is always serialized as firstName. Also you need to add attributes to the original Person class. To avoid this inflexible approach, you need a custom resolver which decides at runtime how/if to serialize a property.


I can use nested dictionaries instead of an array within a dictionary:

Dim dict As New Scripting.Dictionary, item As Variant
Set dict("a") = New Dictionary
dict("a")(0) = 5
For Each key In dict("a")
    Debug.Print dict("a")(key)
Next

Nested Dictionary Change Value Problem, Then you hit "B" and it will change the values of the dictionary in a very specific way. is that it changed the value for every day, ignoring the key for the day. According to these articles, all Arrays are reference types? Can't try right now in this computer, but my first test from your script would be changing  Dude. Use your common sense and the example I just provided: foreach ($results as $key => $item) { if ($item == 'foo') unset($results[$key]); else ($item == 'bar


Dictionary and Set Improvements in Swift 4.0, In the latest release of Swift, dictionaries and sets gain a number of new methods The value for each key is an array of the groceries within that department, If the key is found, its value is returned and the default is ignored. key lookup, while the mutable values collection lets you modify values in place. Summary: Learn how to add, modify, or verify values in a Windows PowerShell array, and discover two easy techniques for sorting your array. Hey, Scripting Guy! I get that arrays are really simple in Windows PowerShell, but it seems that they are so simple that no one ever seems to tell us how to work with them.


Collection Types, Arrays, sets, and dictionaries in Swift are always clear about the types of values after it's created by adding, removing, or changing items in the collection. the removed item (although you can ignore the returned value if you do not need it):. The type of an array has a data type that determines the types of the elements within an array (int, String, float in our case) and a pair of square brackets []. The brackets indicate that we have an array.


How to filter nil values out of the collection types— Swift, So we need to filter those properties when building a dictionary object — First We have no need to edit anything except making our struct to support one a new In case you still want an array of optionals , you can use filter to remove nil  See the example below where I pass a VBA Array by it’s reference to modify it within a separate procedure. Visual Basic 'Test passing an array ByRef (by reference) to a Procedure (Sub) Sub Test() Dim arr() As Long ReDim arr(0) As Long arr(0) = 1 SetArr arr Debug.Print arr(0) 'Result: 10 End Sub 'Change first element of VBA Array to 10 Sub SetArr(ByRef arr) arr(0) = 10 End Sub