Logic App Expressions

Description:

This post will be a reference post for different expressions you can create with Logic Apps.

To Resolve:

1. Expression to convert to local time zone: convertTimeZone(utcnow(),'UTC','Central Standard Time','yyyy_MM_dd_HH_mm_ss_tt')

2. To do a Start-Sleep, insert a Delay element and set it up accordingly. I like to test Conditions by having if true...delay just to see if the IF statement will fire.

3. A common tactic is to take a HTTP Response or something similar and put it in a Compose element. Logic Apps will dynamically put it in a For each element. When using this strategy, it is best to rename the element ( for example: Get-FileContent ) and then access it later by something like outputs('Get-FileContent'). This will create an object that you can reference.

4. I usually follow Compose elements with:
   • A string variable named longDescription with the expression json( first(outputs('Get-FileContent'))) if the Get-Content element outputs something like [{'key':'value', 'key2':'value2'}]
   • An array variable named DescArray with the expression split(variables('longDescription'),',')
   • Another string variable named key with the expression of split(variables('DescArray')[0],':')[1]. This will have the value of value
   • Another string variable named key2 with the expression of split(variables('DescArray')[0],':')[1]. This will have the value of value2
   • What those string are doing is splitting on ‘:’ and grabbing the second element 1 (first element is 0).

5. To split something = split( + variables('myVarName') or outputs('myComposeElementTitle') + ,',')

6. To get an array count: sub(length(outputs('Convert-ToArray')),1) coming from a compose element. Length will get the number of elements, but you need to subtract one because arrays are 0 value so you use sub( length, 1) to subtract the length - 1.

7. To access the last element in array: variables('stringArray')[variables('count')] assuming you have a variable named count using the step above.

8. Working with substrings:

   $test = "Some info: Some value
   
   Some info2: Some value2
   
   Some info3: Some value3
   
   Response successful. Response info4: 12345678"
   

   • Syntax: substring ( string to modify, starting index, integer you want past the index)
   • So if I wanted to get:
   • : 12345678 stored in variable $substring
   • I would use expression: substring(variables('test'),lastIndexOf(variables('test'),':'),sub(length(variables('test')),lastIndexOf(variables('test'),':')))

   substring
   (
      variables('test'), #string to modify
      lastIndexOf(variables('test'),':'), # starting index = get the position of last colon = 210
      sub(length(variables('test')),lastIndexOf(variables('test'),':')) # integer you want past the index = subtract the position of last colon 210 from length of $test 216, so 6
   )
   

   • Which is nice, but let’s substring again to get the first two characters removed:

   # Now we do this again
   substring
   ( 
      variables('substring'), #string to modify
      2, # starting index
      sub(length(variables('substring')),2)) # integer you want past the index = subtract 2 from the length of $substring
   )