Instance Launch failure through Cloud Formation Template

Question

Hello Team,
I'm trying to launch an instance through CF template. However, I'm getting below error while launching:
"Value of property SubnetId must be of type String"
Steps Followed:
1. Created a VPC CF template and defined "Outputs" in the template section as below:

Outputs:

PublicSubnet1:
    Description: Public Subnet 1 ID
    Export:
      Name: !Sub ${AWS::StackName}-PublicSubnet1
    Value: !Ref PublicSubnet1

2. Created an EC2 launch template and in "Resources" section , defined Subnet properties as follows:
    Properties:
          SubnetId:
        - Fn::ImportValue: !Sub ${ExportVpcStackName}-PublicSubnet1

Can anyone please advise what the reason for failure?

Thanks,
Abhishek

kentrad · Answer

Here is the example from the [documentation](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/intrinsic-function-reference-importvalue.html):

```
Resources:
  WebServerInstance:
    Type: 'AWS::EC2::Instance'
    Properties:
      InstanceType: t2.micro
      ImageId: ami-a1b23456
      NetworkInterfaces:
        - GroupSet:
            - Fn::ImportValue: 
              'Fn::Sub': '${NetworkStackNameParameter}-SecurityGroupID'
          AssociatePublicIpAddress: 'true'
          DeviceIndex: '0'
          DeleteOnTermination: 'true'
          SubnetId: Fn::ImportValue 
            'Fn::Sub': '${NetworkStackNameParameter}-SubnetID'
```
It looks like you are presenting an array, '-', as the value to SubnetId.

Instance Launch failure through Cloud Formation Template

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