Power Automate: Generate Custom GUID(s)

/ Charles

Yes, there is a guid() expression available in Power Automate. The provided expression doesn’t accept parameters though, so for some people, there isn’t an easy way to control the GUID formatting. With that in mind, it might be worth creating your own GUID value:

Figure 1 - Power Automate cloud flow logic.
Figure 1 – Power Automate cloud flow logic.

After the cloud flow trigger, initialize a “counter” variable as an Integer. The logic of the cloud flow uses a Do until loop to create the GUID, so this “counter” variable is used to track the number of iterations before exiting the loop:

Figure 2 - Power Automate initialize variable block for vCounter.
Figure 2 – Power Automate initialize variable block for vCounter.

Next, initialize a “length” variable, also as an Integer. This specifies how many characters the GUID should have. Should it be 32 characters? Longer? Shorter?

Figure 3 - Power Automate initialize variable block for vThisGuidLength.
Figure 3 – Power Automate initialize variable block for vThisGuidLength.

Now, the flow needs to initialize an empty String variable for storing the actual GUID value. As the Do until loop processes, pieces of the GUID will be appended to this string variable.

Figure 4 - Power Automate initialize variable block for vThisGuidValue.
Figure 4 – Power Automate initialize variable block for vThisGuidValue.

Switching variable types again, initialize an Array variable for storing the letters of alphabet. To easily populate the array, add a string of comma separated letters, then split() the string using the comma as a delimiter:

Figure 5 - Power Automate initialize variable block for aListOfLetters.
Figure 5 – Power Automate initialize variable block for aListOfLetters.

E.g., 

split('a,b,c,d,e, ... ,v,w,x,y,z', ',')

Finally, getting into the core flow logic, add a Do until action. This action will loop until the “counter” value is greater than the “length” value. Don’t forget to increment the “counter” variable by 1.

Within the loop, add a Switch() step to the flow. In this scenario, the flow generates a random number between 1 and 4, inclusive of the number 1:

rand(1,4)
Figure 6 - Power Automate loop with increment variable action and switch statement.
Figure 6 – Power Automate loop with increment variable action and switch statement.

For those unfamiliar with Switch actions, they’re essentially another type of conditional logic. If-Then statements are binary and often repeat the condition. Taking an alternative approach, switch statements ask for the condition once, then makers can add multiple cases for the condition to evaluate against.

Here, the rand() expression is evaluating a 1, 2 3, or 4. If a “1”, then append a lower-case letter. If a “2”, then append an upper-case letter:

Figure 7 - Switch action for lower-case letters.
Figure 7 – Switch action for lower-case letters.
Figure 8 - Switch action for upper-case letters.
Figure 8 – Switch action for upper-case letters.

Use the array variable from earlier to append the lower- and upper-case letters:

variables('aListOfLetters')

Summarizing the logic of this step, get the length() of the array and subtract 1 because arrays are 0-based. Now, get a rand() number between 0 and the calculated array length, use the take() expression to return a subset of the array, then get the last() item of the subset.

Because the array is already full of lower-case letters, use the toUpper() expression to change the casing.

last(
    take({collection}, 
    rand(0, 
        sub(
            length(variables('aListOfLetters')), 
            1
)    )    )    )

For the last case option, the default, append a random number within the range of 0-9:

rand(0,9)
Figure 9 - Switch case for random number, 0-9.
Figure 9 – Switch case for random number, 0-9.

An optional last step, store the newly created GUID value using a newly initialized flow variable. Why? Because after running the flow, you can review the run log and check the GUID value.

Figure 10 - Power Automate initialize variable block for vGuid.
Figure 10 – Power Automate initialize variable block for vGuid.

E.g., expanded vGuid variable block after a successful run.

Figure 11 - Power Automate vGuid variable after a successful cloud flow run.
Figure 11 – Power Automate vGuid variable after a successful cloud flow run.

Conclusion:
Creating your own GUID value is useful when needing to control the length or characters of the GUID.

“The question of color was but another detail, somewhere between being six feet tall and being six feet under.”

James Baldwin

#BlackLivesMatter

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