How do I reference custom Cloud Formation resources?

I read the documentation for AWS Cloudformation Resources and there’s no mention of how to reference the resources elsewhere in my serverless.yml. It does link to the documentation for using variables from other “stacks”, but what about the current stack?

I figured this out on my own through trial and error, but I want to know why it’s not in the documentation.

You can reference the resources using the !Ref “function”, like so:

provider:
  vpc:
    subnetIds:
      - !Ref privateSubnetA
      - !Ref privateSubnetB

resources:
  Resources:
    privateSubnetA:
      Type: AWS::EC2::Subnet
      Properties:
        VpcId: something
        AvailabilityZone: something
        CidrBlock: something
        MapPublicIpOnLaunch: false
        Tags:
          - Key: Name
            Value: "something"
    privateSubnetB:
      Type: AWS::EC2::Subnet
      Properties:
        VpcId: something
        AvailabilityZone: something
        CidrBlock: something
        MapPublicIpOnLaunch: false
        Tags:
          - Key: Name
            Value: "something"