The MacView

Virtual Instrumentation from a Mac perspective

Thursday, May 06, 2010

How To Automate Creating Large Enums

I was creating some VIs to call the OS to get system colors directly when I ran into an annoyance. The OS defines a long list of constants (in this case kThemeBrush* in Appearance.h on the Mac). I wanted an enum in my VI API to make code calling my VI more readable (right click -> create constant on the enum terminal creates an enum constant on the diagram). There were 62 enum values to enter. This was not something I wanted to type one by one into the enum control. So I came up with a way to automate much of the creation.

First I searched for all lines in Appearance.h that contain kThemeBrush and a number. I took those lines and pasted them into a string constant and then wrote some code to parse out the constant name and value (see diagram below).



So what does this diagram do? First I use vi.lib/AdvancedString/Normalize End Of Line.vi to make sure the line endings in the string are the LabVIEW platform line ending (\r on the Mac). I then use Spreadsheet String To Array primitive to parse the string into lines (one of my favorite text parsing tricks in LabVIEW). Then for each line I get the part before the equals (name of the constant) and then I get the part between the equals and the comma (constant value).

I then copy the Ring to my VI, right click on it and select Replace and replace it with an enum. LabVIEW preserves all the strings. However, to get the appropriate value (enums by default use their (zero based) index as their value) I use the output array.

The front panel of the VI has a Ring (not enum because you can't write the strings to an enum on a running VI). The constant names are written to the Ring values (Strings[]) and we output an array of the constant values. We right click on the array control and select Data Operations -> Copy Data. Then right click on the array constant in the diagram below and select Data Operations -> Paste Data.



This diagram converts the enum values to the constants from the header.

I did this for two separate API calls (Theme Text and Theme Brush), each with their own set of constants. More reliable and much faster than doing it by hand.

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4 Comments:

Blogger TonPlomp said...

The LAVA App Store (or Code Repository) has a tool Variant To Control that allows you to store any kind of variant data as a LabVIEW typedef. It features and example VI that saves an Array of Strings as an enum.

No need to hassle with rings, I have used this tool to create an enum that turns a U8 into it's ASCII representation.

Thursday, May 06, 2010 9:49:00 PM  
Blogger TonPlomp said...

Here's an image of some code you could use: snippet it creates a sparse enum if it's needed. Here's the info on the Array To Enum function.

Thursday, May 06, 2010 11:27:00 PM  
Blogger Marc said...

Good call Ton.

Friday, May 07, 2010 5:49:00 AM  
Blogger Scott Hannahs said...

Hey Marc!

I tried to send you direct email, but it bounced back at me.... So this is a bit off topic.

I just saw your post on Christina's blog. It triggered another item that has been bothering me as well. Once upon a time there was some released code called "Tiger Tools". This had some nice little OS X tools for Spotlight Indexing, VI Viewer Widget, and a few Automator actions.

These have stopped working on Snow Leopard since the Spotlight indexing needs a 64 bit version since it is called by a 64 bit version. The others seem to be working though I haven't used the automator tools. But if that package could be recompiled for fat binaries to support all systems it would be very nice.

I see that NI has removed all references to that package from the site other than my forum post asking about this.

Thanks,
-Scott

Friday, May 07, 2010 7:23:00 PM  

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