Extractor (Falco.UnionRoutes)

Extractor Module

Namespace: Falco.UnionRoutes
Assembly: Falco.UnionRoutes.dll
Parent Module: Extraction

Factory functions for creating extractors to use with EndpointConfig.

Route.endpoints needs to know how to populate each field in your route types:

Built-in types (Guid, string, int, bool) - automatic
Single-case DU wrappers (e.g., PostId of Guid) - automatic
Custom types - use Extractor.parser
PreCondition/OverridablePreCondition fields - use Extractor.precondition (covers both)

Example

 let config: EndpointConfig<AppError> = {
     Preconditions = [ yield! Extractor.precondition<UserId, _> requireAuth ]
     Parsers = [
         Extractor.parser<Slug> (fun s -> Ok (Slug s))                                     // no constraint
         Extractor.constrainedParser<Slug> [| RouteConstraint.Alpha |] (fun s -> Ok (Slug s))  // adds :alpha
         Extractor.typedParser<bool, Toggle> (fun b -> Ok (if b then On else Off))          // adds :bool
     ]
     MakeError = fun msg -> BadRequest msg
     CombineErrors = fun errors -> errors |> List.head
     ToErrorResponse = fun e -> Response.ofPlainText (string e)
 }

val config: 'a

union case Result.Ok: ResultValue: 'T -> Result<'T,'TError>

type bool = System.Boolean

Multiple items
module List from Microsoft.FSharp.Collections

--------------------
type List<'T> = | op_Nil | op_ColonColon of Head: 'T * Tail: 'T list interface IReadOnlyList<'T> interface IReadOnlyCollection<'T> interface IEnumerable interface IEnumerable<'T> member GetReverseIndex: rank: int * offset: int -> int member GetSlice: startIndex: int option * endIndex: int option -> 'T list static member Cons: head: 'T * tail: 'T list -> 'T list member Head: 'T with get member IsEmpty: bool with get member Item: index: int -> 'T with get ...

val head: list: 'T list -> 'T

Multiple items
val string: value: 'T -> string

--------------------
type string = System.String

Functions and values

Function or value	Description
`Extractor.constrainedParser constraints parser` Full Usage: `Extractor.constrainedParser constraints parser` Parameters: constraints : `RouteConstraint[]` - ASP.NET Core route constraints to apply (e.g., Alpha). parser : `Parser<'T>` - Function that parses a string into the target type. Returns: `FieldParser` A FieldParser for EndpointConfig.	Registers a string parser with explicit route constraints. Use this when you want ASP.NET Core to validate the route parameter before your parser runs. For example, `constrainedParser<Slug> [\| RouteConstraint.Alpha \|] slugParser` adds an `:alpha` constraint so only alphabetic values reach the parser. constraints : `RouteConstraint[]` ASP.NET Core route constraints to apply (e.g., Alpha). parser : `Parser<'T>` Function that parses a string into the target type. Returns: `FieldParser` A FieldParser for EndpointConfig.
`Extractor.parser parser` Full Usage: `Extractor.parser parser` Parameters: parser : `Parser<'T>` - Function that parses a string into the type. Returns: `FieldParser` A FieldParser for EndpointConfig.	Registers a parser for a custom type used in route or query parameters. Only needed for custom types. Built-in types and single-case DU wrappers around built-in types are handled automatically. This parser adds no route constraints. Use Extractor.constrainedParser to add constraints (e.g., `:alpha`), or Extractor.typedParser for typed input with implicit constraints. parser : `Parser<'T>` Function that parses a string into the type. Returns: `FieldParser` A FieldParser for EndpointConfig.
`Extractor.precondition extractor` Full Usage: `Extractor.precondition extractor` Parameters: extractor : `Extractor<'T, 'E>` - Async function that extracts the value from HTTP context. Returns: `PreconditionExtractor<'E> list` A list of PreconditionExtractors covering both PreCondition and OverridablePreCondition.	Registers an async extractor for both `PreCondition<'T>` and `OverridablePreCondition<'T>` fields. extractor : `Extractor<'T, 'E>` Async function that extracts the value from HTTP context. Returns: `PreconditionExtractor<'E> list` A list of PreconditionExtractors covering both PreCondition and OverridablePreCondition.
`Extractor.preconditionSync extractor` Full Usage: `Extractor.preconditionSync extractor` Parameters: extractor : `SyncExtractor<'T, 'E>` - Synchronous function that extracts the value from HTTP context. Returns: `PreconditionExtractor<'E> list` A list of PreconditionExtractors covering both PreCondition and OverridablePreCondition.	Registers a sync extractor for both `PreCondition<'T>` and `OverridablePreCondition<'T>` fields. Convenience wrapper that wraps a synchronous extractor in `Task.FromResult`. extractor : `SyncExtractor<'T, 'E>` Synchronous function that extracts the value from HTTP context. Returns: `PreconditionExtractor<'E> list` A list of PreconditionExtractors covering both PreCondition and OverridablePreCondition.
`Extractor.typedParser parser` Full Usage: `Extractor.typedParser parser` Parameters: parser : `'TInput -> Result<'TOutput, string>` - Function that converts the pre-parsed typed value into the target type. Returns: `FieldParser` A FieldParser for EndpointConfig.	Registers a typed parser where the input type determines the implicit route constraint. The parser receives a pre-parsed typed value (not a raw string) because the ASP.NET Core route constraint guarantees the format. For example, a `typedParser<bool, ToggleState>` receives a `bool` value since the `:bool` constraint ensures only valid booleans reach the handler. parser : `'TInput -> Result<'TOutput, string>` Function that converts the pre-parsed typed value into the target type. Returns: `FieldParser` A FieldParser for EndpointConfig.