WithType Interface

Adds a type symbol to a type for stronger typing.

Sealed

This type is "sealed," meaning that code outside of the library defining it should not implement or extend it. Future versions of this type may add members or make typing of readonly members more specific.

Signature

/** @sealed */
export interface WithType<out TName extends string = string, out TKind extends NodeKind = NodeKind, out TInfo = unknown>

Type Parameters

Parameter	Constraint	Default	Description
TName	string	string	Same as TreeNodeSchema's "Name" parameter.
TKind	NodeKind	NodeKind	Same as TreeNodeSchema's "Kind" parameter.
TInfo		unknown	Same as TreeNodeSchema's "Info" parameter: format depends on the Kind.

Remarks

Powers TreeNode's strong typing setup.

Example

Narrow types for overloading based on NodeKind

function getKeys(node: TreeNode & WithType<string, NodeKind.Array>): number[];
function getKeys(node: TreeNode & WithType<string, NodeKind.Map | NodeKind.Object>): string[];
function getKeys(node: TreeNode): string[] | number[];
function getKeys(node: TreeNode): string[] | number[] {
	const schema = Tree.schema(node);
	switch (schema.kind) {
		case NodeKind.Array: {
			const arrayNode = node as TreeArrayNode;
			const keys: number[] = [];
			for (let index = 0; index < arrayNode.length; index++) {
				keys.push(index);
			}
			return keys;
		}
		case NodeKind.Map:
			return [...(node as TreeMapNode).keys()];
		case NodeKind.Object:
			return Object.keys(node);
		default:
			throw new Error("Unsupported Kind");
	}
}

Properties

Property	Alerts	Modifiers	Type	Description
[typeNameSymbol]	Deprecated	readonly	TName	Type symbol, marking a type in a way to increase type safety via strong type checking.
[typeSchemaSymbol]		readonly	TreeNodeSchemaClass<TName, TKind, TreeNode, never, boolean, TInfo>	Type symbol, marking a type in a way to increase type safety via strong type checking.

Property Details

[typeNameSymbol]

Type symbol, marking a type in a way to increase type safety via strong type checking.

This API is deprecated and will be removed in a future release.

Use typeSchemaSymbol instead.

Signature

get [typeNameSymbol](): TName;

Type: TName

[typeSchemaSymbol]

Type symbol, marking a type in a way to increase type safety via strong type checking.

Signature

get [typeSchemaSymbol](): TreeNodeSchemaClass<TName, TKind, TreeNode, never, boolean, TInfo>;

Type: TreeNodeSchemaClass<TName, TKind, TreeNode, never, boolean, TInfo>