Cloudformation SNS template validation error - aws-cloudformation

Question

I am trying to create sns subscription but I am getting template validation error.
'MySNSTopic' is the Logical ID of the cloudformation stack called testsnstopic.
Is this correct. Can anyone explain what value I should give for 'Ref' here
"TopicArn" : {
"Ref": "MySNSTopic"
}
Template validation error:
Template format error: Unresolved resource dependencies [MySNSTopic] in the Resources block of the template
code:
{
"Resources": {
"MySubscription" : {
"Type" : "AWS::SNS::Subscription",
"Properties" : {
"Endpoint" : "test#abc.com",
"Protocol" : "email",
"TopicArn" : {
"Ref": "MySNSTopic"
}
}
}
}
}

Answer 1

To use properties across different stacks, you need to explicitly export the values on the one end and import into the other stack.
In your case you would propably need something like this:
Stack: sns-test
{
"Resources": {
"MySNSTopic": {
"Type": "AWS::SNS::Topic"
}
},
"Outputs": {
"MySNSTopicOutput": {
"Description": "SNS topic arn",
"Value": {
"Ref": "MySNSTopic"
},
"Export": {
"Name": {
"Fn::Sub": "${AWS::StackName}-MySNSTopicExport"
}
}
}
}
}
Stack: sns-subscription
{
"Resources": {
"MySubscription": {
"Type": "AWS::SNS::Subscription",
"Properties": {
"Endpoint": "jens#apimeister.com",
"Protocol": "email",
"TopicArn": {
"Fn::ImportValue" : "sns-test-MySNSTopicExport"
}
}
}
}
}