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createBuilder()

createBuilder<State>(initial): BuilderDefinition<State, object>

Creates an immutable builder definition.

Use .step(name, fn) to add steps, then .done() to get the factory. Each step method on the final builder returns a new builder (immutable).

Type Parameters​

State: State​

The product type being built

Parameters​

initial: State​

The initial state

Returns: BuilderDefinition<State, object>​

A builder definition to chain .step() calls

Since​

2.4.0

Example​

const queryBuilder = createBuilder({ table: "", where: [] as string[], limit: 100 })
  .step("from", (s, table: string) => ({ ...s, table }))
  .step("where", (s, clause: string) => ({ ...s, where: [...s.where, clause] }))
  .step("limit", (s, n: number) => ({ ...s, limit: n }))
  .done();

const q = queryBuilder()
  .from("users")
  .where("active = true")
  .limit(10)
  .build();

BuilderDefinition<State, Methods>​

Interface

Intermediate builder definition that accumulates steps.

Since​

2.4.0

Type Parameters​

State: State​

The product state being built

Methods: Methods extends object​

Accumulated method signatures

Methods​

step()​

Adds a step to the builder.

Type Parameters​

K: K extends string​

The method name

Arg: Arg​

The argument type for this step

name: K — The method name
fn: (state, arg) => State — The step function
Returns: BuilderDefinition<State, Methods & { [P in string]: (arg: Arg) => unknown }>

done()​

Finalizes the definition and returns a builder factory.

Returns​

(): FinalBuilder<State, Methods>

Returns​

FinalBuilder<State, Methods>

FinalBuilder<State, Methods>​

Type

FinalBuilder<State, Methods> = { [K in keyof Methods]: Methods[K] extends (arg: infer Arg) => unknown ? (arg: Arg) => FinalBuilder<State, Methods> : never } & object

The final builder object with chainable step methods.

Type Declaration​

build(): () => State​

Returns the built product.

Returns: State​

current(): () => State​

Returns the current state without finalizing.

Returns: State​

Type Parameters​

State: State​

The product state being built

Methods: Methods extends object​

The step method signatures

Since​

2.4.0

Director()<B, State>​

Type

Director<B, State> = (builder) => object

A Director is a function that orchestrates builder steps in a specific sequence. This is the functional equivalent of the GoF Director class.

Type Parameters​

B: B​

The builder type

State: State​

The product type

Parameters​

builder: B​

Returns: object​

build(): () => State​

Returns: State​

Since​

2.4.0

Example​

// Director as a simple function
const buildSportsCar: Director<ReturnType<typeof carBuilder>, Car> = (b) =>
  b.engine("V8").wheels(4).color("red");

const car = buildSportsCar(carBuilder()).build();