Fn::FindInMap
enhancements
The AWS::LanguageExtensions
transform enhances the functionality of the
Fn::FindInMap
intrinsic function in CloudFormation templates.
The Fn::FindInMap
function is used to retrieve a value from a mapping defined
in the Mappings
section of a CloudFormation template. However, the standard
Fn::FindInMap
function has limitations, such as the inability to handle
missing mappings or use a Fn::FindInMap
function with some intrinsic functions
embedded inside it.
The AWS::LanguageExtensions
transform addresses these limitations by
introducing the following enhancements:
-
Default value support – You can specify a default value to be returned if a mapping is not found.
-
Intrinsic function support – You can also use a wider range of intrinsic functions to define the fields of
Fn::FindInMap
than with the standardFn::FindInMap
function.
Declaration
JSON
{ "Fn::FindInMap" : [ "
MapName
", "TopLevelKey
", "SecondLevelKey
", {"DefaultValue": "DefaultValue
"} ] }
YAML
Syntax for the full function name:
Fn::FindInMap:
- MapName
- TopLevelKey
- SecondLevelKey
- DefaultValue:DefaultValue
Syntax for the short form:
!FindInMap
- MapName
- TopLevelKey
- SecondLevelKey
- DefaultValue:DefaultValue
Parameters
- DefaultValue
-
The value that
Fn::FindInMap
will resolve to if theTopLevelKey
and/orSecondLevelKey
can not be found from theMapName
map. This field is optional.
All parameters MapName
, TopLevelKey
,
SecondLevelKey
, and DefaultValue
can be an intrinsic
function as long as it's able to resolve to a valid value during the transform.
Examples
The following examples demonstrate how to define the fields of
Fn::FindInMap
when you add the AWS::LanguageExtensions
transform.
Using a default value
The following is an example of using a default value in the
Fn::FindInMap
function.
JSON
{ //... "Transform": "AWS::LanguageExtensions", //... "Fn::FindInMap": [ "RegionMap", { "Ref": "AWS::Region" }, "InstanceType", { "DefaultValue": "t3.micro" } ] //... }
YAML
Transform: 'AWS::LanguageExtensions' #... !FindInMap - 'RegionMap' - !Ref 'AWS::Region' - 'InstanceType' - DefaultValue: t3.micro #...
Using intrinsic functions to define the top level key
The following is an example of using a Fn::FindInMap
function
with the Fn::Select
and Fn::Split
intrinsic functions
embedded inside it to define the top level key.
JSON
{ //... "Transform": "AWS::LanguageExtensions", //... "Fn::FindInMap": [ "MyMap", { "Fn::Select": [ 0, { "Fn::Split": [ "|", { "Ref": "InputKeys" } ] } ] }, "SecondKey" ] //... }
YAML
Transform: 'AWS::LanguageExtensions' #... !FindInMap: [MyMap, !Select [0, !Split [|, !Ref InputKeys]], SecondKey] #...
Supported functions
You can use the following functions in the parameters of Fn::FindInMap:
enhancements:
-
Fn::Split
- Unless it’s used for the default value,Fn::Split
has to be used in conjunction with intrinsic functions that produce a string, such asFn::Join
orFn::Select
.
Related resources
For more information and examples that show how to use the Fn::FindInMap
intrinsic function, see Fn::FindInMap.
For more information about the AWS::LanguageExtensions
transform, see
AWS::LanguageExtensions transform.