Check if a property/key exists in JSON output

[sunithav]

I'm using "Invoke HTTP Trigger" action in my flow. Sometimes, this action returns JSON response without some keys.

Could someone help on how to check if keys like  locationUri, locationType exist in the JSON response. 

Condition contains(outputs('Invoke_an_HTTP_request'),'locationUri') did not help.

JSON Response

"location": {
"displayName": "",
"locationUri": "",
"locationType": "conferenceRoom",
"uniqueId": "",
"uniqueIdType": "directory",
"address": {
"street": "",
"city": "",
"state": "",
"countryOrRegion": "",
"postalCode": ""
},
"coordinates": {}
},
"locations": [
{
"displayName": "",
"locationUri": "",
"locationType": "conferenceRoom",
"uniqueId": "",
"uniqueIdType": "directory",
"address": {
"street": "",
"city": "",
"state": "",
"countryOrRegion": "",
"postalCode": ""
},
"coordinates": {}
}
],

[dcafiero]

I have this same problem. How do we handle if a property does not exist? In my example, I always get this error.

InvalidTemplate. Unable to process template language expressions in action 'CurrentHealth' inputs at line '1' and column '2931': 'The template language expression 'if(empty(variables('trackerRows').cells[9].value),variables('trackerRows').cells[9].value,'null')' cannot be evaluated because property 'value' doesn't exist, available properties are 'columnId'. Please see https://aka.ms/logicexpressions for usage details.'.

[dcafiero]

I was able to solve the problem by using an if and then contains. This should solve your issue.

if(contains(variables('trackerRows').cells[9], 'value'), variables('trackerRows').cells[9].value, 'null')

[v-bacao-msft · Accepted solution]

Hi @sunithav ,

You can try to use the property name in Compose to get the property value. If Compose fails, it means that the property does not exist.

https://flow.microsoft.com/en-us/blog/error-handling/

Hope this helps.

Best Regards,

[sunithav]

Hi @v-bacao-msft ,

Thanks for your response.

I converted JSON response to string and used condition to check if string contains the required keyword.

Thanks,

SV

[MartinPyman]

A slightly more elegant solution:

Use the equals function in a condition step equal to false

Example:

equals( variables('JSON')?['<Property to Find>'] , null)

[PabloD]

Very nice! Thank you.

[jensweiltoyota]

Good try but it does not work. You can't access a property that does not exist. 

[MartinPyman]

Flow running successfully and property marked as not existing:

Here is the formula, I'm looking for "bob" which definitely is not in my json object:

Did you give it a try? It'd be great to see why yours might be failing

[3tsolutions]

I wrote a solution to handle missing properties of an object, if it helps

LINK

[bookworm2death]

Make sure you have that ? between the variable and the property, mine didn't work until I noticed I missed that.