resolvePlaceholder abstract method

String? resolvePlaceholder(
  1. String placeholderName
)

Strategy interface for resolving placeholder values in configuration strings.

A PlaceholderResolver is typically used in systems like property resolvers, YAML or .properties processors, and templating engines to resolve values like #{host} or #{user.name}.

If the placeholder cannot be resolved, this interface allows returning null to indicate that no replacement is to be made.

Example

class MapPlaceholderResolver implements PlaceholderResolver {
  final Map<String, String> values;

  MapPlaceholderResolver(this.values);

  @override
  String? resolvePlaceholder(String placeholderName) => values[placeholderName];
}

final resolver = MapPlaceholderResolver({'port': '8080'});
print(resolver.resolvePlaceholder('port')); // 8080

Resolves the supplied placeholderName to its replacement value.

Returns null if no replacement should be made.

This method is typically called by a property placeholder parser or configuration string processor.

  • placeholderName: The name of the placeholder (without #{).
  • Returns: The replacement value, or null if unresolved.

Implementation

/// Resolves the supplied [placeholderName] to its replacement value.
///
/// Returns `null` if no replacement should be made.
///
/// This method is typically called by a property placeholder parser or
/// configuration string processor.
///
/// - [placeholderName]: The name of the placeholder (without `#{`).
/// - Returns: The replacement value, or `null` if unresolved.
String? resolvePlaceholder(String placeholderName);