Table of Contents

Class Fn

Namespace
Amazon.CDK
Assembly
Amazon.CDK.dll

CloudFormation intrinsic functions.

public class Fn : DeputyBase
Inheritance
Fn

Examples

using Amazon.CDK;

             Portfolio portfolio;
             CloudFormationProduct product;


             portfolio.ConstrainCloudFormationParameters(product, new CloudFormationRuleConstraintOptions {
                 Rule = new TemplateRule {
                     RuleName = "testInstanceType",
                     Condition = Fn.ConditionEquals(Fn.Ref("Environment"), "test"),
                     Assertions = new [] { new TemplateRuleAssertion {
                         Assert = Fn.ConditionContains(new [] { "t2.micro", "t2.small" }, Fn.Ref("InstanceType")),
                         Description = "For test environment, the instance type should be small"
                     } }
                 }
             });

Remarks

http://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/intrinsic-function-reference.html

ExampleMetadata: infused

Methods

Base64(string)

The intrinsic function Fn::Base64 returns the Base64 representation of the input string.

public static string Base64(string data)

Parameters

data string

The string value you want to convert to Base64.

Returns

string

a token represented as a string

Remarks

This function is typically used to pass encoded data to Amazon EC2 instances by way of the UserData property.

Cidr(string, double, string?)

The intrinsic function Fn::Cidr returns the specified Cidr address block.

public static string[] Cidr(string ipBlock, double count, string? sizeMask = null)

Parameters

ipBlock string

The user-specified default Cidr address block.

count double

The number of subnets' Cidr block wanted.

sizeMask string

The digit covered in the subnet.

Returns

string[]

a token represented as a string

ConditionAnd(params ICfnConditionExpression[])

Returns true if all the specified conditions evaluate to true, or returns false if any one of the conditions evaluates to false.

public static ICfnRuleConditionExpression ConditionAnd(params ICfnConditionExpression[] conditions)

Parameters

conditions ICfnConditionExpression[]

conditions to AND.

Returns

ICfnRuleConditionExpression

an FnCondition token

Remarks

Fn::And acts as an AND operator. The minimum number of conditions that you can include is 1.

ConditionContains(string[], string)

Returns true if a specified string matches at least one value in a list of strings.

public static ICfnRuleConditionExpression ConditionContains(string[] listOfStrings, string value)

Parameters

listOfStrings string[]

A list of strings, such as "A", "B", "C".

value string

A string, such as "A", that you want to compare against a list of strings.

Returns

ICfnRuleConditionExpression

an FnCondition token

ConditionEachMemberEquals(string[], string)

Returns true if a specified string matches all values in a list.

public static ICfnRuleConditionExpression ConditionEachMemberEquals(string[] listOfStrings, string value)

Parameters

listOfStrings string[]

A list of strings, such as "A", "B", "C".

value string

A string, such as "A", that you want to compare against a list of strings.

Returns

ICfnRuleConditionExpression

an FnCondition token

ConditionEachMemberIn(string[], string[])

Returns true if each member in a list of strings matches at least one value in a second list of strings.

public static ICfnRuleConditionExpression ConditionEachMemberIn(string[] stringsToCheck, string[] stringsToMatch)

Parameters

stringsToCheck string[]

A list of strings, such as "A", "B", "C".

stringsToMatch string[]

A list of strings, such as "A", "B", "C".

Returns

ICfnRuleConditionExpression

an FnCondition token

ConditionEquals(object, object)

Compares if two values are equal.

public static ICfnRuleConditionExpression ConditionEquals(object lhs, object rhs)

Parameters

lhs object

A value of any type that you want to compare.

rhs object

A value of any type that you want to compare.

Returns

ICfnRuleConditionExpression

an FnCondition token

Remarks

Returns true if the two values are equal or false if they aren't.

ConditionIf(string, object, object)

Returns one value if the specified condition evaluates to true and another value if the specified condition evaluates to false.

public static ICfnRuleConditionExpression ConditionIf(string conditionId, object valueIfTrue, object valueIfFalse)

Parameters

conditionId string

A reference to a condition in the Conditions section.

valueIfTrue object

A value to be returned if the specified condition evaluates to true.

valueIfFalse object

A value to be returned if the specified condition evaluates to false.

Returns

ICfnRuleConditionExpression

an FnCondition token

Remarks

Currently, AWS CloudFormation supports the Fn::If intrinsic function in the metadata attribute, update policy attribute, and property values in the Resources section and Outputs sections of a template. You can use the AWS::NoValue pseudo parameter as a return value to remove the corresponding property.

ConditionNot(ICfnConditionExpression)

Returns true for a condition that evaluates to false or returns false for a condition that evaluates to true.

public static ICfnRuleConditionExpression ConditionNot(ICfnConditionExpression condition)

Parameters

condition ICfnConditionExpression

A condition such as Fn::Equals that evaluates to true or false.

Returns

ICfnRuleConditionExpression

an FnCondition token

Remarks

Fn::Not acts as a NOT operator.

ConditionOr(params ICfnConditionExpression[])

Returns true if any one of the specified conditions evaluate to true, or returns false if all of the conditions evaluates to false.

public static ICfnRuleConditionExpression ConditionOr(params ICfnConditionExpression[] conditions)

Parameters

conditions ICfnConditionExpression[]

conditions that evaluates to true or false.

Returns

ICfnRuleConditionExpression

an FnCondition token

Remarks

Fn::Or acts as an OR operator. The minimum number of conditions that you can include is 1.

FindInMap(string, string, string)

The intrinsic function Fn::FindInMap returns the value corresponding to keys in a two-level map that is declared in the Mappings section.

public static string FindInMap(string mapName, string topLevelKey, string secondLevelKey)

Parameters

mapName string
topLevelKey string
secondLevelKey string

Returns

string

a token represented as a string

GetAtt(string, string)

The Fn::GetAtt intrinsic function returns the value of an attribute from a resource in the template.

public static IResolvable GetAtt(string logicalNameOfResource, string attributeName)

Parameters

logicalNameOfResource string

The logical name (also called logical ID) of the resource that contains the attribute that you want.

attributeName string

The name of the resource-specific attribute whose value you want.

Returns

IResolvable

an IResolvable object

GetAzs(string?)

The intrinsic function Fn::GetAZs returns an array that lists Availability Zones for a specified region.

public static string[] GetAzs(string? region = null)

Parameters

region string

The name of the region for which you want to get the Availability Zones.

Returns

string[]

a token represented as a string array

Remarks

Because customers have access to different Availability Zones, the intrinsic function Fn::GetAZs enables template authors to write templates that adapt to the calling user's access. That way you don't have to hard-code a full list of Availability Zones for a specified region.

ImportListValue(string, double, string?)

Like Fn.importValue, but import a list with a known length.

public static string[] ImportListValue(string sharedValueToImport, double assumedLength, string? delimiter = null)

Parameters

sharedValueToImport string
assumedLength double
delimiter string

Returns

string[]

Remarks

If you explicitly want a list with an unknown length, call Fn.split(',', Fn.importValue(exportName)). See the documentation of Fn.split to read more about the limitations of using lists of unknown length.

Fn.importListValue(exportName, assumedLength) is the same as Fn.split(',', Fn.importValue(exportName), assumedLength), but easier to read and impossible to forget to pass assumedLength.

ImportValue(string)

The intrinsic function Fn::ImportValue returns the value of an output exported by another stack.

public static string ImportValue(string sharedValueToImport)

Parameters

sharedValueToImport string

The stack output value that you want to import.

Returns

string

a token represented as a string

Remarks

You typically use this function to create cross-stack references. In the following example template snippets, Stack A exports VPC security group values and Stack B imports them.

Join(string, string[])

The intrinsic function Fn::Join appends a set of values into a single value, separated by the specified delimiter.

public static string Join(string delimiter, string[] listOfValues)

Parameters

delimiter string

The value you want to occur between fragments.

listOfValues string[]

The list of values you want combined.

Returns

string

a token represented as a string

Remarks

If a delimiter is the empty string, the set of values are concatenated with no delimiter.

ParseDomainName(string)

Given an url, parse the domain name.

public static string ParseDomainName(string url)

Parameters

url string

the url to parse.

Returns

string

Ref(string)

The Ref intrinsic function returns the value of the specified parameter or resource.

public static string Ref(string logicalName)

Parameters

logicalName string

The logical name of a parameter/resource for which you want to retrieve its value.

Returns

string

Remarks

Note that it doesn't validate the logicalName, it mainly serves paremeter/resource reference defined in a CfnInclude template.

RefAll(string)

Returns all values for a specified parameter type.

public static string[] RefAll(string parameterType)

Parameters

parameterType string

An AWS-specific parameter type, such as AWS::EC2::SecurityGroup::Id or AWS::EC2::VPC::Id.

Returns

string[]

a token represented as a string array

Select(double, string[])

The intrinsic function Fn::Select returns a single object from a list of objects by index.

public static string Select(double index, string[] array)

Parameters

index double

The index of the object to retrieve.

array string[]

The list of objects to select from.

Returns

string

a token represented as a string

Split(string, string, double?)

Split a string token into a token list of string values.

public static string[] Split(string delimiter, string source, double? assumedLength = null)

Parameters

delimiter string

A string value that determines where the source string is divided.

source string

The string value that you want to split.

assumedLength double?

The length of the list that will be produced by splitting.

Returns

string[]

a token represented as a string array

Remarks

Specify the location of splits with a delimiter such as ',' (a comma). Renders to the Fn::Split intrinsic function.

Lists with unknown lengths (default)

Since this function is used to work with deploy-time values, if assumedLength is not given the CDK cannot know the length of the resulting list at synthesis time. This brings the following restrictions:

    The only valid operation with such a tokenized list is to pass it unmodified to a CloudFormation Resource construct.

    Lists with assumed lengths

    Pass assumedLength if you know the length of the list that will be produced by splitting. The actual list length at deploy time may be longer than the number you pass, but not shorter.

    The returned list will look like:

    [Fn.select(0, split), Fn.select(1, split), Fn.select(2, split), ...]

    The restrictions from the section "Lists with unknown lengths" will now be lifted, at the expense of having to know and fix the length of the list.

    Sub(string, IDictionary<string, string>?)

    The intrinsic function Fn::Sub substitutes variables in an input string with values that you specify.

    public static string Sub(string body, IDictionary<string, string>? variables = null)

    Parameters

    body string

    A string with variables that AWS CloudFormation substitutes with their associated values at runtime.

    variables IDictionary<string, string>

    The name of a variable that you included in the String parameter.

    Returns

    string

    a token represented as a string

    Remarks

    In your templates, you can use this function to construct commands or outputs that include values that aren't available until you create or update a stack.

    Transform(string, IDictionary<string, object>)

    Creates a token representing the Fn::Transform expression.

    public static IResolvable Transform(string macroName, IDictionary<string, object> parameters)

    Parameters

    macroName string

    The name of the macro to perform the processing.

    parameters IDictionary<string, object>

    The parameters to be passed to the macro.

    Returns

    IResolvable

    a token representing the transform expression

    Remarks

    See: https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/intrinsic-function-reference-transform.html

    ValueOf(string, string)

    Returns an attribute value or list of values for a specific parameter and attribute.

    public static string ValueOf(string parameterOrLogicalId, string attribute)

    Parameters

    parameterOrLogicalId string

    The name of a parameter for which you want to retrieve attribute values.

    attribute string

    The name of an attribute from which you want to retrieve a value.

    Returns

    string

    a token represented as a string

    ValueOfAll(string, string)

    Returns a list of all attribute values for a given parameter type and attribute.

    public static string[] ValueOfAll(string parameterType, string attribute)

    Parameters

    parameterType string

    An AWS-specific parameter type, such as AWS::EC2::SecurityGroup::Id or AWS::EC2::VPC::Id.

    attribute string

    The name of an attribute from which you want to retrieve a value.

    Returns

    string[]

    a token represented as a string array