CODEWITHSUNDEEP
amazon-web-servicesaws-cloudformation
vishal
vishal

Reputation: 1874

AWS cft "fn::if" shows error

I'am using the below line in my template

     "ec2instance" : {
"Type" : "AWS::EC2::Instance",
"Properties" : {
        "InstanceType" : {"Ref" : "Publicinstancetype"},
        "ImageId" : "<myimageid>",
        "SubnetId" : { "Fn::If" : ["createpublicsubnet",{"Ref":"publicsubnet"},
        {"Fn::If" : ["createprivatesubnet",{"Ref":"privatesubnet"}]}
        ]}
}

} it is displaying as "Template error: Fn::If requires a list argument with three elements" where am I exactly going wrong? AWS documentations aren't helping. I have specified the conditions perfectly so no need top bother about it

Upvotes: 1

Views: 11192

Answers (2)

Cameron Hudson
Cameron Hudson

Reputation: 3935

Since the Fn::If function requires 3 arguments, you need to use a pseudoparameter:

    "ec2instance" : {
        "Type" : "AWS::EC2::Instance",
        "Properties" : {
            "InstanceType" : {"Ref" : "Publicinstancetype"},
            "ImageId" : "<myimageid>",
            "SubnetId" : {
                "Fn::If" : [
                    "createpublicsubnet",
                    {"Ref" : "publicsubnet"},
                    {"Fn::If" : [
                        "createprivatesubnet",
                        {"Ref" : "privatesubnet"},
                        {"Ref" : "AWS::NoValue"}   // Here
                    ]}
                ]
            }
        }
    }

Upvotes: 2

Usman Azhar
Usman Azhar

Reputation: 864

The Fn:In requires 3 elements and you are giving only 2 parameters.

See the AWS documentation Example . "SecurityGroups" : [{ "Fn::If" : [ "CreateNewSecurityGroup", {"Ref" : "NewSecurityGroup"}, {"Ref" : "ExistingSecurityGroup"} ] }]

"SubnetId" : { "Fn::If" : ["createpublicsubnet",{"Ref":"publicsubnet"},

It should have been "SubnetId" : { "Fn::If" : ["createpublicsubnet",{"Ref":"publicsubnet"}, {"Ref:"privatesubnet"}]}

In your code , it has only two elements been passed as .

Check the AWS documentation correctly. http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/intrinsic-function-reference-conditions.html#intrinsic-function-reference-conditions-if

Upvotes: 3

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