How to create dictionary of dictionaries vbscript

Question

I'm trying to create a dictionary of dictionaries in VBS, and I can get it to work; however, it seems that my sub level dictionary is being accessed by reference instead of by value?

I tried this:

Dim s, fso, f, ts, str, fRead, line, i, dictElements, dictionary, screenItem
Set s = CreateObject("System.Text.StringBuilder")
Set fso = CreateObject("Scripting.FileSystemObject")
Set dictElements = CreateObject("Scripting.Dictionary")
Set dictionary = CreateObject("Scripting.Dictionary")

'add elements to dictionary
dictElements.Add "Name", "MyName"
dictElements.Add "Setpoint", 100.0
dictElements.Add "Process Value", 80.6

'Create Data Structure
dictionary.Add "DigitalInputOne", dictElements
dictionary.Add "DigitalInputTwo", dictElements

'test dictionary
dictionary("DigitalInputTwo")("Name")= "Hello"
dictionary("DigitalInputTwo")("Setpoint")= 40.123
HmiRuntime.Screens("Home").ScreenItems("Text field_1").Text = dictionary ("DigitalInputOne")("Name")
HmiRuntime.Screens("Home").ScreenItems("Text field_2").Text = dictionary("DigitalInputOne")("Setpoint")
HmiRuntime.Screens("Home").ScreenItems("Text field_3").Text = dictionary("DigitalInputOne")("Process Value")

HmiRuntime.Screens("Home").ScreenItems("Text field_4").Text = dictionary("DigitalInputTwo")("Name")
HmiRuntime.Screens("Home").ScreenItems("Text field_5").Text = dictionary("DigitalInputTwo")("Setpoint")
HmiRuntime.Screens("Home").ScreenItems("Text field_6").Text = dictionary("DigitalInputTwo")("Process Value")

When I change one of the values it changes all of the values, which makes me think my elements dictionary is by reference. Is there a way to make this happen by value? I want each sub dictionary to be different.

John Coleman · Accepted Answer · 2016-03-23 15:06:12Z

5

You only have

Set dictElements = CreateObject("Scripting.Dictionary")

once so you are only creating one subdictionary -- and are setting two keys to point to that one subdictionary. Instead, do the following:

Set dictElements = CreateObject("Scripting.Dictionary") 'create first sub-dict
dictionary.Add "DigitalInputOne", dictElements
Set dictElements = CreateObject("Scripting.Dictionary") 'create second sub-dict
dictionary.Add "DigitalInputTwo", dictElements

VBScript has reference-counting based garbage collection. When you add the first dictionary to the top-level dictionary, the top level dictionary now maintains a reference to it. Thus, when you set dictElements equal to a second dictionary, the original dictionary is kept alive by the top-level dictionary, hence it isn't garbage-collected.

edited Mar 23, 2016 at 15:06

answered Mar 23, 2016 at 15:01

John Coleman

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10 Comments

FighterHayabusa Over a year ago

Will this allow me to create a template, or is there a better way to do that? Most of my subdictionaries will be the same, only with different values.

John Coleman Over a year ago

I would write a sub which, when passed a dictionary, initializes it in a certain way. Then follow the 3-step process: 1) create the dictionary, 2) run the initialization sub on it, 3) assign it to the top-level dictionary.

FighterHayabusa Over a year ago

I wanted to use dictElements basically like a data type. I did this, and it works

Set dictionary("DigitalInputOne") = CreateObject("Scripting.Dictionary") Set dictionary("DigitalInputTwo") = CreateObject("Scripting.Dictionary")  For Each item In dictionary     For Each element In dictElements         dictionary(item).Add element, dictElements(element)     Next Next

but I don't think it's very good. I can't use classes because I'm doing this in WinCC.

user692942 Over a year ago

I would use a Class for this and have a Dictionary of Class objects.

John Coleman Over a year ago

@Lankymart You are correct that a custom class provides a good solution to OP's problem. If you flesh out the idea and add it as a second answer I would gladly upvote it.

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