TfArg<T> class sealed

A Terraform argument: a Dart-side literal, a reference to another block's attribute (TfRef), a variable or a raw expression.

T is the Dart type the factory parameter accepts. Resource factories accept TfArg<T> (or TfArg<T>?) for every settable field, so an attribute getter fills one as is: pushEndpoint: api.uri.

Writing arguments

Pick the form by where the value comes from. The argument's type tells you which forms it takes, and a dot shorthand (.literal, .new, .providedAl2023) names the constructor of that type.

The value is Write Example
known when you synth .literal(...) functionName: .literal('hello')
another resource of this Stack (a RefTo<R> input) its ref role: role.ref
one attribute of another block its getter assumeRolePolicy: trust.json
a resource outside this Stack (a RefTo<R> input) .literal(id) zoneId: .literal('023e105f4ecef8ad9ca31a8372d0c353')
one of a fixed set (an enum) the member runtime: .providedAl2023
one of several exclusive arguments (a sealed type) the variant code: .filename(.literal('build/fn.zip'))
a nested block its helper class; .new(...) inside another block or a variant environment: LambdaFunctionEnvironment(...)
a Terraform variable the handle variable<T>() returns memorySize: memory
a variable in an enum or RefTo<R> input .arg(handle) runtime: .arg(runtimeName)
a secret (a Sensitive<T> input) a sensitive variable, never a literal value: .value(dbPassword)
a reference inside a literal list or map the getter's .interpolation {'ROLE_ARN': role.arn.interpolation}
anything else Terraform evaluates .expression(...) .expression(r'${file("trust.json")}') 
final memory = variable<num>('memory_mb');
final runtimeName = variable<String>('runtime');
final dbPassword = variable<String>('db_password', sensitive: true);

final trust = add(
  DataAwsIamPolicyDocument(
    'trust',
    statement: [
      DataIamPolicyDocumentStatement(
        actions: .literal(['sts:AssumeRole']),
        principals: [
          .new(
            type: .literal('Service'),
            identifiers: .literal(['lambda.amazonaws.com']),
          ),
        ],
      ),
    ],
  ),
);
final role = add(AwsIamRole('hello', assumeRolePolicy: trust.json));
add(
  AwsLambdaFunction(
    'hello',
    functionName: .literal('hello'),
    role: role.ref,
    runtime: .arg(runtimeName),
    code: .filename(.literal('build/fn.zip')),
    memorySize: memory,
    environment: LambdaFunctionEnvironment(
      variables: .literal({'ROLE_ARN': role.arn.interpolation}),
    ),
  ),
);
add(
  AwsSsmParameter(
    'db_password',
    name: .literal('/hello/db_password'),
    type: .securestring,
    value: .value(dbPassword),
  ),
);
Implementers
Available extensions

Constructors

TfArg.literal(T value)
A Dart value: .literal('orders'), TfArg.literal('orders') (T inferred) or TfArg<String?>.literal(null) (explicit). A const constructor, so a helper built from literals can be const.
const
factory

Properties

hashCode → int
The hash code for this object.
no setterinherited
runtimeType → Type
A representation of the runtime type of the object.
no setterinherited

Methods

encodeAs(String attribute) → TfArg<Object?>

Available on TfArg<List<RefTo<R>>>, provided by the RefToList extension

The argument value: each element's RefTo.encodeAs for a literal list, the value itself otherwise.
noSuchMethod(Invocation invocation) → dynamic
Invoked when a nonexistent method or property is accessed.
inherited
toString() → String
A string representation of this object.
inherited
toTfJson() → Object?
Value emitted into Terraform JSON.

Operators

operator ==(Object other) → bool
The equality operator.
inherited

Static Methods

duration(Duration duration) → TfArg<String>
Convenience for Terraform duration-string fields (rotation_period, message_retention_duration, ack_deadline_seconds when expressed in string-seconds form, etc.).
expression<T>(String template) → TfArg<T>
Convenience: TfArg.expression(r'${lower(var.name)}-x') (T inferred) or TfArg.expression<int>(r'${var.replicas * 2}') (explicit).
variable<T>(String name) → TfArg<T>
var.<name> by name: .variable('db_password').
workspace<T>() → TfArg<T>
Convenience: TfArg.workspace() — the name of the selected Terraform workspace, ${terraform.workspace}.

Constants

workspaceTemplate → const String
The template workspace emits: ${terraform.workspace}.