ConfigBuilder

1 min read

Import: import system.config;

Read the usage guide for examples and common tasks. This reference lists the public declarations for this part of the library. See Reading API signatures for parameter and result notation.

ConfigBuilder

Merges defaults, JSON files, environment variables, and explicit CLI values in that order.

public class ConfigBuilder

constructor

Creates an empty builder; source precedence is independent of method call order.

public constructor()

default_value

Registers a known setting and its lowest-precedence default.

public fun default_value(key: string, value: string): ConfigBuilder

require

Adds a required known setting with no default.

public fun require(key: string): ConfigBuilder

json_file

Adds a JSON object file; later files override earlier files.

public fun json_file(path: string): ConfigBuilder

environment

Reads known settings from prefix plus the uppercase key, with hyphens replaced by underscores.

public fun environment(prefix: string = ""): ConfigBuilder

cli

Uses explicitly supplied command-line arguments, excluding parser defaults.

public fun cli(arguments: ParsedArguments): ConfigBuilder

validate

Adds a value predicate; false returns a provenance-aware validation error.

public fun validate(key: string, predicate: fun(string): bool): ConfigBuilder

build

Loads and validates a snapshot; failures never change a previously built configuration.

public fun build(): Result<Config, ConfigError>