CfnJson¶

class aws_cdk.core.CfnJson(scope, id, *, value)¶

Bases: aws_cdk.core.Construct

Captures a synthesis-time JSON object a CloudFormation reference which resolves during deployment to the resolved values of the JSON object.

The main use case for this is to overcome a limitation in CloudFormation that does not allow using intrinsic functions as dictionary keys (because dictionary keys in JSON must be strings). Specifically this is common in IAM conditions such as StringEquals: { lhs: "rhs" } where you want “lhs” to be a reference.

This object is resolvable, so it can be used as a value.

This construct is backed by a custom resource.

ExampleMetadata: infused

Example:

tag_param = CfnParameter(self, "TagName")

string_equals = CfnJson(self, "ConditionJson",
    value={
        "f"aws:PrincipalTag/{tagParam.valueAsString}"": True
    }
)

principal = iam.AccountRootPrincipal().with_conditions({
    "StringEquals": string_equals
})

iam.Role(self, "MyRole", assumed_by=principal)

Parameters

scope (Construct) –
id (str) –
value (Any) – The value to resolve. Can be any JavaScript object, including tokens and references in keys or values.

Methods

resolve(_)¶

Produce the Token’s value at resolution time.

Parameters

_ –

Return type

Any

to_json()¶

This is required in case someone JSON.stringifys an object which refrences this object. Otherwise, we’ll get a cyclic JSON reference.

Return type: str

to_string()¶

Returns a string representation of this construct.

Return type: str

Attributes

creation_stack¶

The creation stack of this resolvable which will be appended to errors thrown during resolution.

This may return an array with a single informational element indicating how to get this property populated, if it was skipped for performance reasons.

Return type: List[str]

node¶

The construct tree node associated with this construct.

Return type: ConstructNode

value¶

An Fn::GetAtt to the JSON object passed through value and resolved during synthesis.

Normally there is no need to use this property since CfnJson is an IResolvable, so it can be simply used as a value.

Return type: Reference

Static Methods

classmethod is_construct(x)¶

Return whether the given object is a Construct.

Parameters

x (Any) –

Return type

bool