Environment Slicing

Mon, 01 Jan 0001 00:00:00 +0000

Environment Slicing (The Record Pattern)

The Record Pattern is the most common way to manage dependencies in FsFlow. It uses standard F# records to define the “world” a workflow lives in.

Projecting from the Environment

When a workflow needs a dependency, it “reads” it from the environment record.

type AppEnv = 
    { Gateway: IPingGateway
      Logger: ILogger }

let ping =
    flow {
        // 'env' is the full AppEnv record
        let! gateway = Flow.read (fun env -> env.Gateway)
        return! gateway.Ping()
    }

The Shorthand: `_.Field`

F# provides a nice shorthand for these simple projections. Instead of (fun env -> env.Gateway), you can write _.Gateway. This makes the code much cleaner and easier to read.

Capabilities (CAPS)

Mon, 01 Jan 0001 00:00:00 +0000

Capabilities (CAPS)

The CAPS pattern lets you decouple your workflows from specific record types. Instead of saying “I need the AppEnv record,” a workflow says “I need any environment that provides an IClock.”

This is achieved using the Needs<'dep> interface and the Env<'dep> request token.

Requesting a Dependency with `Env<'dep>`

In a CAPS workflow, you use the Env<'dep> token to request a dependency by its type. FsFlow handles finding that dependency in the environment for you.

Managing Dependencies on FsFlow

Environment Slicing

Environment Slicing (The Record Pattern)

Projecting from the Environment

The Shorthand: _.Field

Capabilities (CAPS)

Capabilities (CAPS)

Requesting a Dependency with Env<'dep>

The Shorthand: `_.Field`

Requesting a Dependency with `Env<'dep>`