Examples of Fn::ForEach in the Resources section - AWS CloudFormation
Replicate an Amazon SNS resourceReplicate an Amazon DynamoDB resourceReplicate multiple resourcesReplicate multiple resources using a nested Fn::ForEach loopsReference replicated properties for an Amazon EC2 resourceReplicate properties for an Amazon EC2 resourcePassing non-alphanumeric characters within the Collection for Fn::ForEach

This is the new AWS CloudFormation Template Reference Guide. Please update your bookmarks and links. For help getting started with CloudFormation, see the AWS CloudFormation User Guide.

Examples of Fn::ForEach in the Resources section

These examples demonstrate using the Fn::ForEach intrinsic function in the Resources section. For more information about this section, see Resources in the AWS CloudFormation User Guide.

Replicate an Amazon SNS resource

This example snippet returns a list of four Amazon SNS topics, with the logical ID corresponding to the items in the collection (Success, Failure, Timeout, Unknown), with a matching TopicName and FifoTopic set to true.

Note

For templates that need to work with both FIFO and standard topics, you can use the DisplayName property instead of TopicName. This allows CloudFormation to automatically generate topic names with the appropriate .fifo suffix when FifoTopic is true. Simply replace TopicName with DisplayName: !Ref TopicName in the Properties section.

JSON

{
    "AWSTemplateFormatVersion": "2010-09-09",
    "Transform": "AWS::LanguageExtensions",
    "Resources": {
        "Fn::ForEach::Topics": [
            "TopicName",
            ["Success", "Failure", "Timeout", "Unknown"],
            {
                "SnsTopic${TopicName}": {
                    "Type": "AWS::SNS::Topic",
                    "Properties": {
                        "TopicName": {"Fn::Sub": "${TopicName}.fifo"},
                        "FifoTopic": true
                    }
                }
            }
        ]
    }
}

YAML

AWSTemplateFormatVersion: 2010-09-09
Transform: AWS::LanguageExtensions
Resources:
  'Fn::ForEach::Topics':
    - TopicName
    - [Success, Failure, Timeout, Unknown]
    - 'SnsTopic${TopicName}':
        Type: 'AWS::SNS::Topic'
        Properties:
          TopicName: !Sub '${TopicName}.fifo'
          FifoTopic: true

The transformed template will be equivalent to the following template:

AWSTemplateFormatVersion: 2010-09-09
Resources:
  SnsTopicSuccess:
    Type: AWS::SNS::Topic
    Properties:
      TopicName: Success.fifo
      FifoTopic: true
  SnsTopicFailure:
    Type: AWS::SNS::Topic
    Properties:
      TopicName: Failure.fifo
      FifoTopic: true
  SnsTopicTimeout:
    Type: AWS::SNS::Topic
    Properties:
      TopicName: Timeout.fifo
      FifoTopic: true
  SnsTopicUnknown:
    Type: AWS::SNS::Topic
    Properties:
      TopicName: Unknown.fifo
      FifoTopic: true

Replicate an Amazon DynamoDB resource

This example snippet creates four AWS::DynamoDB::Table resources with names such as Points, Score, etc.

JSON

{
    "AWSTemplateFormatVersion": "2010-09-09",
    "Transform": "AWS::LanguageExtensions",
    "Resources": {
        "Fn::ForEach::Tables": [
            "TableName",
            ["Points", "Score", "Name", "Leaderboard"],
            {
                "DynamoDB${TableName}": {
                    "Type": "AWS::DynamoDB::Table",
                    "Properties": {
                        "TableName": {
                            "Ref": "TableName"
                        },
                        "AttributeDefinitions": [
                            {
                                "AttributeName": "id",
                                "AttributeType": "S"
                            }
                        ],
                        "KeySchema": [
                            {
                                "AttributeName": "id",
                                "KeyType": "HASH"
                            }
                        ],
                        "ProvisionedThroughput": {
                            "ReadCapacityUnits": "5",
                            "WriteCapacityUnits": "5"
                        }
                    }
                }
            }
        ]
    }
}

YAML

AWSTemplateFormatVersion: 2010-09-09
Transform: AWS::LanguageExtensions
Resources:
  'Fn::ForEach::Tables':
    - TableName
    - [Points, Score, Name, Leaderboard]
    - 'DynamoDB${TableName}':
        Type: 'AWS::DynamoDB::Table'
        Properties:
          TableName: !Ref TableName
          AttributeDefinitions:
            - AttributeName: id
              AttributeType: S
          KeySchema:
            - AttributeName: id
              KeyType: HASH
          ProvisionedThroughput:
            ReadCapacityUnits: '5'
            WriteCapacityUnits: '5'

The transformed template will be equivalent to the following template:

AWSTemplateFormatVersion: 2010-09-09
Transform: AWS::LanguageExtensions
Resources:
  DynamoDBPoints:
    Type: AWS::DynamoDB::Table
    Properties:
      TableName: Points
      AttributeDefinitions:
        - AttributeName: id
          AttributeType: S
      KeySchema:
        - AttributeName: id
          KeyType: HASH
      ProvisionedThroughput:
        ReadCapacityUnits: '5'
        WriteCapacityUnits: '5'
  DynamoDBScore:
    Type: AWS::DynamoDB::Table
    Properties:
      TableName: Score
      AttributeDefinitions:
        - AttributeName: id
          AttributeType: S
      KeySchema:
        - AttributeName: id
          KeyType: HASH
      ProvisionedThroughput:
        ReadCapacityUnits: '5'
        WriteCapacityUnits: '5'
  DynamoDBName:
    Type: AWS::DynamoDB::Table
    Properties:
      TableName: Name
      AttributeDefinitions:
        - AttributeName: id
          AttributeType: S
      KeySchema:
        - AttributeName: id
          KeyType: HASH
      ProvisionedThroughput:
        ReadCapacityUnits: '5'
        WriteCapacityUnits: '5'
  DynamoDBLeaderboard:
    Type: AWS::DynamoDB::Table
    Properties:
      TableName: Leaderboard
      AttributeDefinitions:
        - AttributeName: id
          AttributeType: S
      KeySchema:
        - AttributeName: id
          KeyType: HASH
      ProvisionedThroughput:
        ReadCapacityUnits: '5'
        WriteCapacityUnits: '5'

Replicate multiple resources

This example creates multiple instances of AWS::EC2::NatGateway and AWS::EC2::EIP using a naming convention of "{ResourceType}${Identifier}". You can declare multiple resource types under one Fn::ForEach loop to take advantage of a single identifier.

Unique values for each element in the collection are defined within the Mappings section, where the Fn::FindInMap intrinsic function is used to reference the corresponding value. If Fn::FindInMap is unable to find the corresponding identifier, the Condition property will not be set resolving to !Ref AWS:::NoValue.

JSON

{
  "AWSTemplateFormatVersion": "2010-09-09",
  "Transform": "AWS::LanguageExtensions",
  "Conditions": {
    "TwoNatGateways": {"Fn::Equals": [{"Ref": "AWS::Region"}, "us-east-1"]},
    "ThreeNatGateways": {"Fn::Equals": [{"Ref": "AWS::Region"}, "us-west-2"]}
  },
  "Mappings": {
    "NatGateway": {
      "Condition": {
        "B": "TwoNatGateways",
        "C": "ThreeNatGateways"
      }
    }
  },
  "Resources": {
    "VPC": {
      "Type": "AWS::EC2::VPC",
      "Properties": {"CidrBlock": "10.0.0.0/16"}
    },
    "PublicSubnetA": {
      "Type": "AWS::EC2::Subnet",
      "Properties": {
        "VpcId": {"Ref": "VPC"},
        "CidrBlock": "10.0.1.0/24",
        "AvailabilityZone": {"Fn::Select": [0, {"Fn::GetAZs": ""}]}
      }
    },
    "PublicSubnetB": {
      "Type": "AWS::EC2::Subnet",
      "Properties": {
        "VpcId": {"Ref": "VPC"},
        "CidrBlock": "10.0.2.0/24",
        "AvailabilityZone": {"Fn::Select": [1, {"Fn::GetAZs": ""}]}
      }
    },
    "PublicSubnetC": {
      "Type": "AWS::EC2::Subnet",
      "Properties": {
        "VpcId": {"Ref": "VPC"},
        "CidrBlock": "10.0.3.0/24",
        "AvailabilityZone": {"Fn::Select": [2, {"Fn::GetAZs": ""}]}
      }
    },
    "Fn::ForEach::NatGatewayAndEIP": [
      "Identifier",
      [ "A", "B", "C" ],
      {
        "NatGateway${Identifier}": {
          "Type": "AWS::EC2::NatGateway",
          "Properties": {
            "AllocationId": {"Fn::GetAtt": [{"Fn::Sub": "NatGatewayAttachment${Identifier}"}, "AllocationId"]},
            "SubnetId": {"Ref": {"Fn::Sub": "PublicSubnet${Identifier}"}}
          },
          "Condition": {"Fn::FindInMap": ["NatGateway", "Condition", {"Ref": "Identifier"}, {"DefaultValue": {"Ref": "AWS::NoValue"}}]}
        },
        "NatGatewayAttachment${Identifier}": {
          "Type": "AWS::EC2::EIP",
          "Properties": {
            "Domain": "vpc"
          },
          "Condition": {"Fn::FindInMap": ["NatGateway", "Condition", {"Ref": "Identifier"}, {"DefaultValue": {"Ref": "AWS::NoValue"}}]}
        }
      }
    ]
  }
}

YAML

AWSTemplateFormatVersion: 2010-09-09
Transform: AWS::LanguageExtensions
Conditions:
  TwoNatGateways: !Equals [!Ref "AWS::Region", "us-east-1"]
  ThreeNatGateways: !Equals [!Ref "AWS::Region", "us-west-2"]
Mappings:
  NatGateway:
    Condition:
      B: TwoNatGateways
      C: ThreeNatGateways
Resources:
  VPC:
    Type: AWS::EC2::VPC
    Properties:
      CidrBlock: 10.0.0.0/16
  PublicSubnetA:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref VPC
      CidrBlock: 10.0.1.0/24
      AvailabilityZone: !Select [0, !GetAZs ""]
  PublicSubnetB:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref VPC
      CidrBlock: 10.0.2.0/24
      AvailabilityZone: !Select [1, !GetAZs ""]
  PublicSubnetC:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref VPC
      CidrBlock: 10.0.3.0/24
      AvailabilityZone: !Select [2, !GetAZs ""]
  Fn::ForEach::NatGatewayAndEIP:
    - Identifier
    - - A
      - B
      - C
    - NatGateway${Identifier}:
        Type: AWS::EC2::NatGateway
        Properties:
          AllocationId: !GetAtt
            - !Sub NatGatewayAttachment${Identifier}
            - AllocationId
          SubnetId: !Ref
            Fn::Sub: PublicSubnet${Identifier}
        Condition: !FindInMap
          - NatGateway
          - Condition
          - !Ref Identifier
          - DefaultValue: !Ref AWS::NoValue
      NatGatewayAttachment${Identifier}:
        Type: AWS::EC2::EIP
        Properties:
          Domain: vpc
        Condition: !FindInMap
          - NatGateway
          - Condition
          - !Ref Identifier
          - DefaultValue: !Ref AWS::NoValue

The transformed template will be equivalent to the following template:

AWSTemplateFormatVersion: 2010-09-09
Transform: AWS::LanguageExtensions
Conditions:
  TwoNatGateways: !Equals [!Ref "AWS::Region", "us-east-1"]
  ThreeNatGateways: !Equals [!Ref "AWS::Region", "us-west-2"]
Resources:
  VPC:
    Type: AWS::EC2::VPC
    Properties:
      CidrBlock: 10.0.0.0/16
  PublicSubnetA:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref VPC
      CidrBlock: 10.0.1.0/24
      AvailabilityZone: !Select [0, !GetAZs ""]
  PublicSubnetB:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref VPC
      CidrBlock: 10.0.2.0/24
      AvailabilityZone: !Select [1, !GetAZs ""]
  PublicSubnetC:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref VPC
      CidrBlock: 10.0.3.0/24
      AvailabilityZone: !Select [2, !GetAZs ""]
  NatGatewayA:
    Type: AWS::EC2::NatGateway
    Properties:
      AllocationId: !GetAtt
        - NatGatewayAttachmentA
        - AllocationId
      SubnetId: !Ref PublicSubnetA
  NatGatewayB:
    Type: AWS::EC2::NatGateway
    Properties:
      AllocationId: !GetAtt
        - NatGatewayAttachmentB
        - AllocationId
      SubnetId: !Ref PublicSubnetB
    Condition: TwoNatGateways
  NatGatewayC:
    Type: AWS::EC2::NatGateway
    Properties:
      AllocationId: !GetAtt
        - NatGatewayAttachmentC
        - AllocationId
      SubnetId: !Ref PublicSubnetC
    Condition: ThreeNatGateways
  NatGatewayAttachmentA:
    Type: AWS::EC2::EIP
    Properties:
      Domain: vpc
  NatGatewayAttachmentB:
    Type: AWS::EC2::EIP
    Properties:
      Domain: vpc
    Condition: TwoNatGateways
  NatGatewayAttachmentC:
    Type: AWS::EC2::EIP
    Properties:
      Domain: vpc
    Condition: ThreeNatGateways

Replicate multiple resources using a nested Fn::ForEach loops

This example uses nested Fn::ForEach loops to map three resources ( AWS::EC2::NetworkAcl, AWS::EC2::Subnet, and AWS::EC2::SubnetNetworkAclAssociation) with each other.

JSON

{
  "AWSTemplateFormatVersion": "2010-09-09",
  "Transform": "AWS::LanguageExtensions",
  "Resources": {
    "VPC": {
      "Type": "AWS::EC2::VPC",
      "Properties": {
        "CidrBlock": "10.0.0.0/16",
        "EnableDnsSupport": "true",
        "EnableDnsHostnames": "true"
      }
    },
    "Fn::ForEach::SubnetResources": [
      "Prefix",
      [
        "Transit",
        "Public"
      ],
      {
        "Nacl${Prefix}Subnet": {
          "Type": "AWS::EC2::NetworkAcl",
          "Properties": {
            "VpcId": {
              "Ref": "VPC"
            }
          }
        },
        "Fn::ForEach::LoopInner": [
          "Suffix",
          [
            "A",
            "B",
            "C"
          ],
          {
            "${Prefix}Subnet${Suffix}": {
              "Type": "AWS::EC2::Subnet",
              "Properties": {
                "VpcId": {
                  "Ref": "VPC"
                }
              }
            },
            "Nacl${Prefix}Subnet${Suffix}Association": {
              "Type": "AWS::EC2::SubnetNetworkAclAssociation",
              "Properties": {
                "SubnetId": {
                  "Ref": {
                    "Fn::Sub": "${Prefix}Subnet${Suffix}"
                  }
                },
                "NetworkAclId": {
                  "Ref": {
                    "Fn::Sub": "Nacl${Prefix}Subnet"
                  }
                }
              }
            }
          }
        ]
      }
    ]
  }
}

YAML

AWSTemplateFormatVersion: 2010-09-09
Transform: AWS::LanguageExtensions
Resources:
  VPC:
    Type: AWS::EC2::VPC
    Properties:
      CidrBlock: 10.0.0.0/16
      EnableDnsSupport: 'true'
      EnableDnsHostnames: 'true'
  'Fn::ForEach::SubnetResources':
  - Prefix
  - [Transit, Public]
  - 'Nacl${Prefix}Subnet':
      Type: 'AWS::EC2::NetworkAcl'
      Properties:
        VpcId: !Ref 'VPC'
    'Fn::ForEach::LoopInner':
    - Suffix
    - [A, B, C]
    - '${Prefix}Subnet${Suffix}':
        Type: 'AWS::EC2::Subnet'
        Properties:
          VpcId: !Ref 'VPC'
      'Nacl${Prefix}Subnet${Suffix}Association':
        Type: 'AWS::EC2::SubnetNetworkAclAssociation'
        Properties:
          SubnetId: !Ref
            'Fn::Sub': '${Prefix}Subnet${Suffix}'
          NetworkAclId: !Ref
            'Fn::Sub': 'Nacl${Prefix}Subnet'

The transformed template will be equivalent to the following template:

AWSTemplateFormatVersion: 2010-09-09
Transform: AWS::LanguageExtensions
Resources:
  VPC:
    Type: AWS::EC2::VPC
    Properties:
      CidrBlock: 10.0.0.0/16
      EnableDnsSupport: 'true'
      EnableDnsHostnames: 'true'
  NaclTransitSubnet:
    Type: AWS::EC2::NetworkAcl
    Properties:
      VpcId: !Ref VPC
  TransitSubnetA:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref VPC
  NaclTransitSubnetAAssociation:
    Type: AWS::EC2::SubnetNetworkAclAssociation
    Properties:
      SubnetId: !Ref TransitSubnetA
      NetworkAclId: !Ref NaclTransitSubnet
  TransitSubnetB:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref VPC
  NaclTransitSubnetBAssociation:
    Type: AWS::EC2::SubnetNetworkAclAssociation
    Properties:
      SubnetId: !Ref TransitSubnetB
      NetworkAclId: !Ref NaclTransitSubnet
  TransitSubnetC:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref VPC
  NaclTransitSubnetCAssociation:
    Type: AWS::EC2::SubnetNetworkAclAssociation
    Properties:
      SubnetId: !Ref TransitSubnetC
      NetworkAclId: !Ref NaclTransitSubnet
  NaclPublicSubnet:
    Type: AWS::EC2::NetworkAcl
    Properties:
      VpcId: !Ref VPC
  PublicSubnetA:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref VPC
  NaclPublicSubnetAAssociation:
    Type: AWS::EC2::SubnetNetworkAclAssociation
    Properties:
      SubnetId: !Ref PublicSubnetA
      NetworkAclId: !Ref NaclPublicSubnet
  PublicSubnetB:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref VPC
  NaclPublicSubnetBAssociation:
    Type: AWS::EC2::SubnetNetworkAclAssociation
    Properties:
      SubnetId: !Ref PublicSubnetB
      NetworkAclId: !Ref NaclPublicSubnet
  PublicSubnetC:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref VPC
  NaclPublicSubnetCAssociation:
    Type: AWS::EC2::SubnetNetworkAclAssociation
    Properties:
      SubnetId: !Ref PublicSubnetC
      NetworkAclId: !Ref NaclPublicSubnet

Reference replicated properties for an Amazon EC2 resource

This example uses the Fn::ForEach intrinsic function to reference replicated AWS::EC2::Instance resources.

JSON

{
  "AWSTemplateFormatVersion": "2010-09-09",
  "Transform": "AWS::LanguageExtensions",
  "Mappings": {
    "Instances": {
      "InstanceType": {
        "B": "m5.4xlarge",
        "C": "c5.2xlarge"
      },
      "ImageId": {"A": "ami-id1"}
    }
  },
  "Resources": {
    "Fn::ForEach::Instances": [
      "Identifier",
      [
        "A",
        "B",
        "C"
      ],
      {
        "Instance${Identifier}": {
          "Type": "AWS::EC2::Instance",
          "Properties": {
            "InstanceType": {"Fn::FindInMap": ["Instances", "InstanceType", {"Ref": "Identifier"}, {"DefaultValue": "m5.xlarge"}]},
            "ImageId": {"Fn::FindInMap": ["Instances", "ImageId", {"Ref": "Identifier"}, {"DefaultValue": "ami-id-default"}]}
          }
        }
      }
    ]
  },
  "Outputs": {
    "SecondInstanceId": {
      "Description": "Instance Id for InstanceB",
      "Value": {"Ref": "InstanceB"}
    },
    "SecondPrivateIp": {
      "Description": "Private IP for InstanceB",
      "Value": {
        "Fn::GetAtt": [
          "InstanceB",
          "PrivateIp"
        ]
      }
    }
  }
}

YAML

AWSTemplateFormatVersion: 2010-09-09
Transform: AWS::LanguageExtensions
Mappings:
  Instances:
    InstanceType:
      B: m5.4xlarge
      C: c5.2xlarge
    ImageId:
      A: ami-id1
Resources:
  'Fn::ForEach::Instances':
  - Identifier
  - [A, B, C]
  - 'Instance${Identifier}':
      Type: 'AWS::EC2::Instance'
      Properties:
        InstanceType: !FindInMap [Instances, InstanceType, !Ref 'Identifier', {DefaultValue: m5.xlarge}]
        ImageId: !FindInMap [Instances, ImageId, !Ref 'Identifier', {DefaultValue: ami-id-default}]
Outputs:
  SecondInstanceId:
    Description: Instance Id for InstanceB
    Value: !Ref 'InstanceB'
  SecondPrivateIp:
    Description: Private IP for InstanceB
    Value: !GetAtt [InstanceB, PrivateIp]

The transformed template will be equivalent to the following template:

AWSTemplateFormatVersion: 2010-09-09
Transform: AWS::LanguageExtensions
Resources:
  InstanceA:
    Type: AWS::EC2::Instance
    Properties:
      InstanceType: m5.xlarge
      ImageId: ami-id1
  InstanceB:
    Type: AWS::EC2::Instance
    Properties:
      InstanceType: m5.4xlarge
      ImageId: ami-id-default
  InstanceC:
    Type: AWS::EC2::Instance
    Properties:
      InstanceType: c5.2xlarge
      ImageId: ami-id-default
Outputs:
  SecondInstanceId:
    Description: Instance Id for InstanceB
    Value: !Ref InstanceB
  SecondPrivateIp:
    Description: Private IP for InstanceB
    Value: !GetAtt [InstanceB, PrivateIp]

Replicate properties for an Amazon EC2 resource

This example uses the Fn::ForEach intrinsic function to repeat some properties like ImageId, InstanceType, and AvailabilityZone to an AWS::EC2::Instance resource.

JSON

{
  "AWSTemplateFormatVersion": "2010-09-09",
  "Transform": "AWS::LanguageExtensions",
  "Mappings": {
    "InstanceA": {
      "Properties": {
        "ImageId": "ami-id1",
        "InstanceType": "m5.xlarge"
      }
    },
    "InstanceB": {
      "Properties": {
        "ImageId": "ami-id2"
      }
    },
    "InstanceC": {
      "Properties": {
        "ImageId": "ami-id3",
        "InstanceType": "m5.2xlarge",
        "AvailabilityZone": "us-east-1a"
      }
    }
  },
  "Resources": {
    "Fn::ForEach::Instances": [
      "InstanceLogicalId",
      [ "InstanceA", "InstanceB", "InstanceC" ],
      {
        "${InstanceLogicalId}": {
          "Type": "AWS::EC2::Instance",
          "Properties": {
            "DisableApiTermination": true,
            "UserData": {
              "Fn::Base64": {
                "Fn::Join": [
                  "",
                  [
                    "#!/bin/bash\n",
                    "yum update -y\n",
                    "yum install -y httpd.x86_64\n",
                    "systemctl start httpd.service\n",
                    "systemctl enable httpd.service\n",
                    "echo \"Hello World from $(hostname -f)\" > /var/www/html/index.html\n"
                  ]
                ]
              }
            },
            "Fn::ForEach::Properties": [
              "PropertyName",
              [ "ImageId", "InstanceType", "AvailabilityZone" ],
              {
                "${PropertyName}": {
                  "Fn::FindInMap": [
                    { "Ref": "InstanceLogicalId" },
                    "Properties",
                    { "Ref": "PropertyName"},
                    {
                      "DefaultValue": { "Ref": "AWS::NoValue" }
                    }
                  ]
                }
              }
            ]
          }
        }
      }
    ]
  }
}

YAML

AWSTemplateFormatVersion: 2010-09-09
Transform: AWS::LanguageExtensions
Mappings:
  InstanceA:
    Properties:
      ImageId: ami-id1
      InstanceType: m5.xlarge
  InstanceB:
    Properties:
      ImageId: ami-id2
  InstanceC:
    Properties:
      ImageId: ami-id3
      InstanceType: m5.2xlarge
      AvailabilityZone: us-east-1a
Resources:
  'Fn::ForEach::Instances':
  - InstanceLogicalId
  - [InstanceA, InstanceB, InstanceC]
  - '${InstanceLogicalId}':
      Type: 'AWS::EC2::Instance'
      Properties:
        DisableApiTermination: true
        UserData:
          Fn::Base64: !Sub |
            #!/bin/bash
            yum update -y
            yum install -y httpd.x86_64
            systemctl start httpd.service
            systemctl enable httpd.service
            echo "Hello World from $(hostname -f)" > /var/www/html/index.html
        'Fn::ForEach::Properties':
          - PropertyName
          - [ImageId, InstanceType, AvailabilityZone]
          - '${PropertyName}':
             'Fn::FindInMap':
               - Ref: 'InstanceLogicalId'
               - Properties
               - Ref: 'PropertyName'
               - {DefaultValue: !Ref 'AWS::NoValue'}

The transformed template will be equivalent to the following template:

AWSTemplateFormatVersion: 2010-09-09
Transform: AWS::LanguageExtensions
Resources:
  InstanceA:
    Type: AWS::EC2::Instance
    Properties:
      DisableApiTermination: true
      UserData:
        Fn::Base64: 
          !Sub |
            #!/bin/bash
            yum update -y
            yum install -y httpd.x86_64
            systemctl start httpd.service
            systemctl enable httpd.service
            echo "Hello World from $(hostname -f)" > /var/www/html/index.html
      ImageId: ami-id1
      InstanceType: m5.xlarge
  InstanceB:
    Type: AWS::EC2::Instance
    Properties:
      DisableApiTermination: true
      UserData:
        Fn::Base64: 
          !Sub |
            #!/bin/bash
            yum update -y
            yum install -y httpd.x86_64
            systemctl start httpd.service
            systemctl enable httpd.service
            echo "Hello World from $(hostname -f)" > /var/www/html/index.html
      ImageId: ami-id2
  InstanceC:
    Type: AWS::EC2::Instance
    Properties:
      DisableApiTermination: true
      UserData:
        Fn::Base64: 
          !Sub |
            #!/bin/bash
            yum update -y
            yum install -y httpd.x86_64
            systemctl start httpd.service
            systemctl enable httpd.service
            echo "Hello World from $(hostname -f)" > /var/www/html/index.html
      ImageId: ami-id3
      InstanceType: m5.2xlarge
      AvailabilityZone: us-east-1a

Passing non-alphanumeric characters within the Collection for Fn::ForEach

This example uses the &{} syntax, which allows the non-alphanumeric characters (. and /) in the IP addresses to be passed within the Collection.

JSON

{
    "AWSTemplateFormatVersion": "2010-09-09",
    "Transform": "AWS::LanguageExtensions",
    "Parameters": {
        "IpAddresses": {
            "Type": "CommaDelimitedList",
            "Default": "10.0.2.0/24,10.0.3.0/24,10.0.4.0/24"
        }
    },
    "Resources": {
        "VPC": {
            "Type": "AWS::EC2::VPC",
            "Properties": {
                "CidrBlock": "10.0.0.0/16",
                "EnableDnsSupport": "true",
                "EnableDnsHostnames": "true"
            }
        },
        "Fn::ForEach::Subnets": [
            "CIDR",
            {
                "Ref": "IpAddresses"
            },
            {
                "Subnet&{CIDR}": {
                    "Type": "AWS::EC2::Subnet",
                    "Properties": {
                        "VpcId": {
                            "Ref": "VPC"
                        },
                        "CidrBlock": {
                            "Ref": "CIDR"
                        }
                    }
                }
            }
        ]
    }
}

YAML

AWSTemplateFormatVersion: 2010-09-09
Transform: AWS::LanguageExtensions
Parameters:
  IpAddresses:
    Type: CommaDelimitedList
    Default: '10.0.2.0/24,10.0.3.0/24,10.0.4.0/24'
Resources:
  VPC:
    Type: AWS::EC2::VPC
    Properties:
      CidrBlock: 10.0.0.0/16
      EnableDnsSupport: 'true'
      EnableDnsHostnames: 'true'
  'Fn::ForEach::Subnets':
    - CIDR
    - !Ref IpAddresses
    - 'Subnet&{CIDR}':
        Type: 'AWS::EC2::Subnet'
        Properties:
          VpcId: !Ref VPC
          CidrBlock: !Ref CIDR

The transformed template will be equivalent to the following template:

AWSTemplateFormatVersion: 2010-09-09
Transform: AWS::LanguageExtensions
Parameters:
  IpAddresses:
    Type: CommaDelimitedList
    Default: '10.0.2.0/24,10.0.3.0/24,10.0.4.0/24'
Resources:
  VPC:
    Type: AWS::EC2::VPC
    Properties:
      CidrBlock: 10.0.0.0/16
      EnableDnsSupport: 'true'
      EnableDnsHostnames: 'true'
  Subnet1002024:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref VPC
      CidrBlock: 10.0.2.0/24
  Subnet1003024:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref VPC
      CidrBlock: 10.0.3.0/24
  Subnet1004024:
    Type: AWS::EC2::Subnet
    Properties:
      VpcId: !Ref VPC
      CidrBlock: 10.0.4.0/24