Need help in fixing this CloudFormation Template for ALB - amazon-web-services

Question

This is a CloudFormation template to create application load balancer.
I'm getting an error that says- Value of property Subnets must be of type List of String.
Are the security group entities declared rightly?
AWSTemplateFormatVersion: '2010-09-09'
Parameters:
Name:
Description: Name of the project
Type: String
Environment:
Description: Environment of the Application Load balancer
Type: String
PublicSubnet:
Description: Subnet
Type: List<AWS::EC2::Subnet::Id>
Vpc:
Description: VPC
Type: AWS::EC2::VPC::Id
Resources:
SecurityGroup:
Type: AWS::EC2::SecurityGroup
Properties:
GroupDescription: ElastiCache Security Group
VpcId: !Ref Vpc
SecurityGroupIngress:
-
IpProtocol: tcp
FromPort: "80"
ToPort: "80"
FromPort: "443"
ToPort: "443"
CidrIp: "0.0.0.0/0"
Tags:
-
Key: Name
Value: "App-SG"
ApplicationLB:
Type: 'AWS::ElasticLoadBalancingV2::LoadBalancer'
Properties:
IpAddressType: ipv4
Name: Test-ALB
Scheme: internet-facing
SecurityGroups:
- !Ref SecurityGroup
Subnets:
- !Ref PublicSubnet
Tags:
- Key: Name
Value: Test-ALB
Type: application
ALBListener:
Type: 'AWS::ElasticLoadBalancingV2::Listener'
Properties:
DefaultActions:
- Type: forward
TargetGroupArn: !Ref ALBTargetGroup
LoadBalancerArn:
Ref: ApplicationLB
Port: '80'
Protocol: HTTP
ALBTargetGroup:
Type: 'AWS::ElasticLoadBalancingV2::TargetGroup'
Properties:
HealthCheckIntervalSeconds: 30
HealthCheckTimeoutSeconds: 5
HealthyThresholdCount: 3
Port: 80
Protocol: HTTP
UnhealthyThresholdCount: 5
VpcId: !Ref Vpc
Also it would be helpful to review the entire template, incase there are more errors.

Answer 1

Your PublicSubnet is already a list. So you can just do:
Subnets: !Ref PublicSubnet